Important Questions

Punjab State Board PSEB 9th Class Science Important Questions Chapter 10 Gravitation Important Questions and Answers.

PSEB 9th Class Science Important Questions Chapter 10 Gravitation

Long Answer Type Questions:

Question 1.
Define Newton’s universal law of gravitation and establish mathematical formula for force of attraction between two objects.
Answer:
Newton’s universal law of gravitation-Every particle in this universe attracts each and every particle, the force of attraction is:
1. directly proportional to the product of both the masses.
2. Inversely proportional of the square of the distance between the two. This force always acts along the line joining the two masses.

Derivation of Mathematical Formula: From the fig. Jet there are two balls A and B having masses m₁ and m₂ distance between them is ‘r’.
According to Newton’s third law of motion ball A exerts a force FAB on the ball B and ball B exerts a force FBA on the ball A. These forces are equal and opposite

where G is universal gravitational constant. This is named so since its numerical value remains constant in whole of the universe and the formula is known as Newton’s universal law’ of gravitation.
Value of G
G = 6.67 × 10^-11 Nm²/kg²

Question 2.
Write Kepler’s law in context with the motion of planets.
Answer:

By the 16th centuary, a lot of data on the motion of planets had been collected by many astronomers. Johannes Kepler derived three law s based on these data. These are known as Kepler’s laws. These are:
1. Law of orbits (First laws): The orbit of a planet is an ellipse and the sun is at one of the foci, as shown in fig. In this fig. Sun is shown at O.

2. Law of area (Second laws): The line joining the planet and sun sweep equal areas in equal interv als of time. Thus, time taken for the motion from A to B is same as for the motion from C to D and area OAB and OCD are equal.

3. Law of time period (Third law): The cube of mean distance of a planet from the sun is directly proportional to square of its orbital time period
T² ∝ r³
But Kepler could not give a theory which explained the motion of planets.
Newton showed that due to motion of planets sun exerts force of gravtation on them.
i.e. T²/r³ = constant.

Question 3.
How did Robert Boyle proved experimentally that all bodies fall in vacuum with same acceleration?
Or
How did Robert Boyle show experimentally that a coin and a piece of paper when dropped simultaneously from same height in vacuum fall with same acceleration?
Answer:
Boyle’s Experiment: As shown in fig. Robert Boyle took a long glass tube. A heavy coin and a piece of paper were placed inside the tube. The ends of the tube were closed. Air from the tube was removed with the help of a vacuum pump.

When the tube was quickly inverted it was seen that coin and a piece of paper hit the bottom of the tube at the same time. Now the experiment was repeated with air inside the glass tube. This time it was observed that a piece of paper falls slowly whereas the coin immediately hit the bottom of glass tube. This experiment proves that in vacuum all bodies irrespective of their masses (both light and heavy) fall towards earth with same acceleration

Question 4.
(a) Prove that acceleration due to gravity is independent of mass.
(b) Find the value of ‘g’.
Answer:
(a) Consider a body of mass ‘m’ lying on the surface of earth. Suppose M and R are respectively mass and radius of earth.
Let F be the force of gravity acting on the body

This acceleration is called acceleration due to gravity
∴ g = \(\frac{G M}{R^{2}}\)
This equation is free from mass ‘m’. This shows that due to force of gravity the acceleration produced in an object is independent of its mass.

(b) To find the value of ‘g’
G = 6.67 × 10 “n Nm2/kg2
R = 6400 km
= 6400 × 1000 m
= 64 × 105 m
= 6.4 × 106 m
Mass of the earth(M) = 6 × 1024 kg
But g = \(\frac{G M}{R^{2}}\)
= \(\frac{6.67 \times 10^{-11} \times 6 \times 10^{24}}{\left(6.4 \times 10^{6}\right)^{2}}\)
or g = 9.8 ms^-2

Question 5.
Describe those factors which are responsible for variation in the value of acceleration due to gravity ‘g’?
Answer:
Variation in the value of acceleration due to following factors:
Variation in g with altitude-Value of ‘g’ is maximum on the surface of earth. As we move in the upward direction (higher altitudes) value of ‘g’ goes on decreasing. We can calculate value of ‘g at altitude using mathematical formula. If
g_e = acceleration due to gravity on the surface of earth
g_h = acceleration due to gravity at height h
R = radius of earth
we know g_h = g_e\(\left[\frac{\mathrm{R}^{2}}{(\mathrm{R}+h)^{2}}\right]\)
If we know value of h, we can calculate g_h.
Special case-If ‘h’ is half the value of radius of earth i.e. h = \(\frac {R}{2}\) then

Another interesting fact that value of ‘g’ is zero at the centre of earth.

2. Variation in g due to shape of earth-
Earth is not exactly spherical. It is somewhat egg-shaped. Its radius at poles is less than that at equator as shown in fig.

As shown in fig. radius of earth at equator is 6378 km and radius of earth at poles is 6357 km. Thus, value of g at poles is g_p = 9.831 m s_-2 (maximum) and minimum value at equator is g_e = 9.782 m s_-2. We use average value of g calculated from g_e, and g_p.

3. Effect of depth: If we go deep under the earth e.g. in caves or in mines, value of ‘g’ i’ decreased. Value of g goes on decreasing, if depth goes on increasing. At the centre of earth, value of g is zero.
\(\frac{\mathrm{W}_{d}}{\mathrm{~W}_{e}}=\frac{g_{d}}{g_{e}}=\left[1-\frac{d}{\mathrm{R}}\right]\)

Question 6.
Establish the relation between ‘g’ and ‘G’.
Or
Deduce an expression for it in terms of mass of the earth ‘M’ and universal gravitational constant ‘G’.
Or
Show that the acceleration due to gravity of an object is independent of its mass.
Answer:

Relation between ‘g’ and ‘G’. Suppose the earth is a sphere of mass M and radius R, Consider a body of mass m lying at a distance ‘r’ from the centre of the earth. According to Newton’s law of gravitation, the force of attraction between the earth and the body,
F = \(\frac{\mathrm{GM} m}{r^{2}}\) ……………… (i)
Tills force of gravity produces an acceleration ‘g’, is the body of mass m.
Hence, from Newton’s second law,
F = Mass × Acceleration
F = m × g ……………..(ii)
From equations (i) and (ii) we get
mg = \(\frac{\mathrm{GM} m}{r^{2}}\)
or g = \(\frac{\mathrm{GM}}{r^{2}}\) ………..(iii)
This equation gives relation between acceleration due to gravity ‘g’ at points far away from the earth and gravitational constant ‘G’.
Since (3) does not involve’m’ it is therefore eviden t that ‘g’ does not depend upon the mass of the body.

Question 7.
What is Archimedes principle? How can you verify it experimentally? Also write applications of Archimedes principle.
Answer:
Archimedes Principle: According to this principle when a solid body is immersed either completely or partially in a liquid, it experiences an upward thrust which is equal to the weight of the liquid displaced by the immersed part of the body.”

Experimental Verification: Take a stone piece and tie it to the hook of a spring balance. Hold the spring balance in your hand or support it from the stand so as to suspend the stone piece as shown in fig.

Note, the reading on the spring balance to know the weight of the stone. Now pour some water a beaker with and slowly immerse the stone in the water while remaining tied with the hook of spring balance as shown in fig. (b). You will see that spring balance shows a decreased reading i.e. weight of stone is decreased after it is immersed in the water.

Subtract the two readings to know the decrease in the weight of stone. As soon as the stone is immersed in the water it displaces water equal to its own volume. Collect this water in other beaker and measure its weight. You will find that this weight of water is equal to the decrease of weight of the stone. Thus Archimedes principle is proved.

Applications of Archimedes’ Principle:

1. Archimedes principle is used in designing ships and submarines.
2. Lactometers are constructed on Archimedes’ Principle which are used to measure puritv of a sample of milk.
3. Hydrometers used to measure density of liquid are also based on Archimedes principle.

Short Answer Type Questions:

Question 1.
Which one is greater-the gravitational force of the earth on 1 kg iron or the force of gravitation applied by 1 kg on earth?
Answer:
According to Newton’s law of Gravitation there exists of mutual force of attraction between two objects. Since the mass of iron is less than the mass of the earth, therefore earth attracts 1 kg mass towards it with a greater force which is noticeable.

Question 2.
Why is G called universal gravitational constant?
Answer:
G is called universal gravitational constant because its numerical value is same in the whole universe. This value is G = 6.67 x 10^-11 Nm²/kg².

Question 3.
Is the value of ‘g’ at a given place same for different bodies or it is variable?
Answer:
From the relation between the acceleration due to gravity ‘g’ and universal gravitational constant G, we know g = \(\frac{\mathrm{GM}}{\mathrm{R}^{2}}\)
From this equation it is evident that the value of ‘g’ does not depend upon the mass of the body. Thus we reach a conclusion that at a given place the value of g is same for different bodies.

Question 4.
Why does a body becomes weightless at the centre of earth?
Answer:
We know value of g goes on decreasing as we continue moving deep into the earth and value of acceleration due to gravity (g) = 0 at the centre of earth. Thus, a body whose mass is m,
Weight of body = m × 0 = 0
Therefore, body becomes weightless.

Question 5.
A tennis ball jumps higher at hills than at planes. Explain.
Answer:
Value of g decreases with altitude, thus gravitational force acting on ball at hills is less as a result ball jumps higher at hills than at planes.

Question 6.
The weight of an object on the surface of earth is 9.8 N. What does this statement mean?
Answer:
We know that value of ‘g’ on the surface of earth is 9.8 m/s² and the relation for weight of an object is:
w = m × g
9.8 = m × 9.8
or m = \(\frac {9.8}{9.8}\)
∴ m = 1 kg
The given statement therefore means the mass of the object on earth is 1 kg.

Question 7.
What type of motion a freely falling body execute under gravity?
Answer:
A body falling freely under gravity executes uniform accelerated motion. If bodies with different masses and different shapes are allowed to fall freely in vacuum, they all will have same acceleration due to gravity.

Question 8.
Give points of difference between Acceleration due to gravity (g) and Universal gravitational constant'(G).
Answer:
Difference between g and G:

Acceleration due to gravity (g)	Gravitational constant (G)
1. It represents acceleration acquired by the body due to gravity.	It represents force of attraction between two masses of 1 kg each lying 1 m apart.
2. Its value is different at different places on earth surface.	Its value is constant at all places. Thus, it is called universal constant.
3. Its value at the surface of earth is 9.8 m/s2.	Its value is 9.67 × 10-11 Nm2kg-2.
4. It is a vector quantity.	It is a scalar quantity.

Question 9.
You buy W weight of sugar at a place situated on equitorial line and then take it to Antarctica. Will that sugar weigh same there? If not whether it would be more or less.
Answer:
The value of ‘g’ at Antarctica is not same as on equator. The value of ‘g’ increases on Antarctica therefore, sugar bought at any place on equitorial line when taken to Antarctica would have more weight but its mass will remain the same because mass is a constant quantity.

Question 10.
Why cannot we move a finger without disturbing all the stars?
Answer:
When we move our finger, then distance between finger and all other things in the universe change and as a result force of gravitation also changes. Thus, all the things get disturbed, although this disturbance is negligible.

Question 11.
Distinguish between Gravitation and Gravity.
Answer:

• Gravitation: Gravitation is the force of attraction between any two bodies in the universe. The attraction between the sun and the earth, the attraction between a table and a chair are examples of gravitation.
• Gravity: Gravity is a special case of gravitation when one of the two bodies is the earth. Gravity is the attraction between the earth and any object lying on or near its surface. A ball thrown upward falls back on the surface of the earth due to earth’s force of gravity.

Question 12.
Explain why a small piece of stone is not attracted towards another big place of stone on the earth’s surface?
Answer:
Because of very small value of G, the force of attraction between any two such ordinary sized bodies is so small that it cannot produce motion in them.

Question 13.
The earth attracts an apple. Does the apple also attract with earth? If it does, why does the earth not move towards the apple?
Answer:
The apple also attracts the earth with an equal and opposite force. The mass of the earth is very large compared to that of apple. So, the acceleration produced in earth is very small as compared to that in the apple. Hence, the motion of the earth towards the apple is not appreciable and therefore, is not noticeable.

Question 14.
If the force of gravity somehow vanishes today, why would we be sent being in space?
Answer:
In the absence of force of gravity, the centripetal force required to keep us rotating along the earth would not be available. As a result would fly off along the tangent to with into the space.

Question 15.
What is meant by density and relative density?
Answer:
Density of a substance is defined as the mass of a substance contained in a unit volume.
Density = \(\frac{\text { Mass }}{\text { Volume }}\)
Its SI unit is kg m^-3.

Relative density or specific gravity is the ratio of density of substance to the density of same volume of water
R.D or S.G = \(\frac{\text { Density of substance }}{\text { Density of water }}\)

Density of water is 1,000 kg m^-3 in SI.
According to Archimedes’ principle, when a body is immersed in water, the loss of weight in water is equal to the weight of an equal volume of water, i.e., weight of water displaced. Hence R.D. can be written as
R.D = \(\frac{\text { Weight of substance }}{\text { Loss of weight of body in water }}\)

Question 16.
What do you mean by buoyancy and centre of buoyancy? In which direction does the buoyant force on an object immersed in a liquid act?
Answer:
Buoyancy: When a body is immersed partially or wholly in a fluid (liquid or gas), it displaces fluid. The displaced fluid exerts an upward force on the body.

The upward force acting on a body imnu rsed in a fluid is called upthrust or force of buoyancy and the phenomenon is called buoyancy. The buoyancy acts through the centre of gravity of the displaced fluid which is called centre of buoyancy.

Question 17.
State Archimedes’ principle.
Answer:
Archimedes’ Principle. When a solid body is immersed completely or partially in a fluid, it experiences an upward thrust which is equal to the weight of the fluid displaced by the immersed part of the body.

Question 18.
Name two forces which act on a body immersed in a liquid. Give the directions in which they act.
Answer:
Two forces which act on a body immersed in a liquid are:

• Weight of the body acting downward.
• An upthrust due to displaced liquid.

Question 19.
How is submarine able to move on water surface as well as go under water?
Answer:
To move submarine under water, water is pumped in its special tanks. This causes a net increase in weight and thus submarine goes down in water.

To bring the submarine upon the surface of sea, the water from the tanks is thrown out by pumps. When water from the tanks of submarine is taken out, the net weight of the submarine decreases without any change in its volume and it comes up on the surface of water.

Question 20.
Give reason when Big buildings and dams have wide foundations for safety.
Answer:
Dams and big buildings have wide foundations for safety, because they may not collapse under high pressure of the building.

Question 21.
A steel needle sinks in water but a steel ship floats. Explain how?
Answer:
A steel needle sinks in water because it displaces less weight of water which provides less buoyant force than the actual weight of the needle. On the other hand, steel ship floats because it displaces a large weight of water which provides a greater buoyant force to keep it a float.

Question 22.
Give reasons for the following :
(a) A sharp blade is more effective in cutting an object than a blunt blade.
(b) A cork piece floats but an iron piece sinks in water.
Answer:
(a) We know Pressure = \(\frac{\text { Thrust }}{\text { Area }}\). For the given thrust, pressure ∝ \(\frac{\text { 1 }}{\text { Area }}\). Thus the effect of the same magnitude of force is more when the area of surface in contact is less. Hence a sharp blade is more effective in cutting an object than a blunt blade.
(b) The density of the cork piece is less than the density of water, and the. density of the iron piece is more than the density of water. Hence, the cork piece floats but the iron piece sinks in water.

Question 23.
Explain the following:
(a) Swimmers are provided with an inflated rubber jacket.
(b) It is easier of swim in sea water than in river water.
Answer:
(a) Swimmers are provided with an inflated rubber jacket to increase the volume such that density is decreased, which is helpful for swimming.
(b) It is easier to swim in sea water than in river water because density of sea water is more than water of the needle sinks in a river while a ship float on it.

Question 24.
Why is the pressure on ground more when a man is walking than when he is standing?
Answer:
When the man stands he exerts a force on the ground equal to his own weight. But when he walks, he pushes the ground backward and exerts an additional force on the ground. That is why pressure on the ground is more when a man is walking than when he is standing.

Question 25.
Why a bucket of water is lighter when in water than when it is taken out of water?
Answer:
Inside water, the bucket experiences upthrust exerted by displaced water, so its apparent weight becomes less than the actual weight. When bucket is taken out of water, upthrust on the bucket disappears and it feels heavier.

Question 26.
If a fresh egg is put into a beaker filled with water, it sinks. On dissolving a lot of salt in the water, the egg begins to rise and floats. Why?
Answer:
The average density of a fresh egg is more than that of pure water but less than that water in which salt is dissolved. So a fresh egg sinks in pure water while it floats in salty water.

Important Formulae:

1. F = G\(\frac{\mathrm{M} m}{\mathrm{R}^{2}}\)
2. F = mg
3. g = G\(\frac{\mathrm{M}}{\mathrm{R}^{2}}\)
4. υ = u +gt
5. υ² = u² + 2gh
6. h = ut + \(\frac {1}{2}\)gt²
7. g_m = \(\frac {1}{6}\)g_e
   (g_m = Acceleration due to gravity on moon , g_e = Acceleration due to gravity on earth)

Necessary Data-
Earth
Mass = 6 × 10²⁴ Kg
Radius = 6.4 × 10⁶ m (6400 Km)
Distance from Sun = 1.5 × 10¹¹ m
Moon
Mass = 7.3 × 10²² Kg

Numerical Problems (Solved):

Question 1.
Two spheres of 1 kg mass each are separated by 3 m. Calculate the gravitational force between then. Given G = 6.67 × 10^-11 Nm²/kg².
Solution:
Here m₁= m₂ = 1 kg
Distance between two spheres, (r) = 3 m
Gravitational constant (G) = 6.67 × 10^-11 Nm²/kg²
We know

Question 2.
The radius of moon is 1.7 × 10⁶ m and its mass is 7.35 × 10²² kg. What is the acceleration due to gravity on the surface of moon? Given G = 6.67 × 10^-11 Nm²/kg²
Solution:
Radius of moon, (R) = 1.7 × 10⁶ m
Mass of moon, (M) = 7.35 × 10²² kg
Gravitational constant, (G) = 6.67 × 10^-11 Nm²/kg² (Given)
We know, Acceleration due to gravity on moon

Question 3.
Find the change in weight percentage of a body when it is taken from equator to poles. Polar radius is 6357km and equitorial radius is 6378km.
Solution:
Polar radius, (r) = 6357 km
Equitorial radius (R) = 6378 km
∴ h = R – r
⇒ h = (6378 – 6357)km
h = 21km
R = 6400 km(Approx)

Question 4.
At what height above the earth surface, the acceleration due to gravity will be half that on the surface of earth? Suppose R is the radius of earth.
Solution:
Let h be the height above earth surface where

Question 5.
A ball is dropped from top of 40 m high tower. What will be its velocity after covering a distance of 20 m ? What will be its velocity on striking the earth?
Answer:
1. Here, height of the tower, (h) = 40 m
Initial velocity, (u) = 0
Acceleration due to gravity, (g) = 10m/s²
Distance covered (S) = 20m

i.e. Velocity of ball when it strikes the earth. = 20 m/s

Question 6.
If weight of an object is 49 N then what will be its mass?
Solution:
Weight of the object W = 49 N
g = 9.8 m s^-2
We know, weight = Mass × acceleration due to gravity
W = m × g
49 = m × 9.8
or m = \(\frac {49}{9.8}\)
∴ m = 5 kg

Question 7.
Ah object is projected vertically upward with a velocity of 50 m/s. After what time the object will attain the maximum height.
Solution:
Initial velocity of the object (u) = 50 m/s [upward direction]
Acceleration due to gravity, (g) = – 10 ms^-2 [object comes to rest]
Velocity of the object at maximum height,
(υ) = 0
Time taken (t) =?
We know, υ = u + gt
0 = 50 + (-10) × t
0 = 50 – 10t
or 10t = 50
∴ t = \(\frac {50}{10}\) = 5s
So the object will attain its maximum height after 5 seconds.

Question 8.
A stone is dropped from the edge of a rooftop. If it crosses 2 m high window in 0.1 second then what is the distance between the upper end of window and the roof?
Solution:

Distance covered in crossing the window
(S) = 2 m
g = 9.8 ms^-2
t = 0.1 s
Let υ be the velocity of the stone when it reaches the upper edge A of the window.

Question 9.
A helicopter drops food packet for people caught in stationary boat. This is moving at a height of 20 m with a horizontal velocity of 2 m/s. When food packet is dropped the nearest end of the boat is just below the helicopter. If boat is 5 m long shall people caught in the boat receive the dropped food packets?
Solution:
h = 20 m, u = 2 m/s g = 10ms^-2
Vertical Range (R) = \(\frac{2 \sqrt{2 h}}{g}\)
= \(\frac{2 \sqrt{2 \times 20}}{10}\)
= 2\( \sqrt{{4}} \)
= 2 × 2 = 4 m
But lenght of boat, = 5m
So people caught in the boat will receive food packets.

Question 10.
An object of volume V is immersed in a liquid of density ρ. Calculate the magnitude of buoyant force acting on the object due to the liquid.
Solution:
By Archimedes’ principle, the magnitude of buoyant force,
U.F. = Weight of liquid displaced = Volume × Density × g or
or U.F. = Vρg

Question 11.
The pressure exerted by the weight of a cubical block of side 4 cm on the surface is 10 pascal. Calculate the weight of the block.
Solution:
Here pressure exerted, P = 10 pascal = 10 Nm^-2,
Area, A = 4 cm × 4 cm
= 16 × 10^-4 m²
As P = \(\frac {F}{A}\)
= \(\frac {W}{A}\)
W = P × A
= 10 Nm^-2 × 16 × 10^-4m²
= 1.6 × 10^-2 N

Question 12.
The volume of a 500 g sealed packet is 350 cm³. Will the packet float or sink in water if the density of water is 1 g cm^-3? What will be the piass of the water displaced by this packet?
Solution:
Mass of packet = 500 g
Volume of packet = 350 cm³.
Density of packet = \(\frac{\text { Mass }}{\text { Volume }}\)
= \(\frac{500 \mathrm{~g}}{350 \mathrm{~cm}^{3}}\)
= 1.43 g cm^-3
Since its density (1.43 g cm^-3) is more than that of water (1 g cm^-3) thus, the sealed packet will sink in water
Volume of water displaced = Volume of packet
= 350 cm³
Mass of water displaced = Volume × Density
= 350 cm³ × 1gcm^-3
= 350 g

Question 13.
A block of wood is kept on the table top. The mass of wooden block is 5 kg and its dimensions are 40 cm × 20 cm × 10 cm. Find the pressure exerted by the wooden block on the table top if it is made to lie on the table top with its sides of dimensions (a) 20 cm × 10 cm and (b) 40 cm × 20 cm.
Solution:
Here, M = 5kg and g = 9.9 ms^-2
Weight = force exerted on table top
= mg
= 5 × 9.8
= 49 N

Question 14.
A solid body floating in water has \(\frac {1}{6}\)th of its volume above the surface.
What fraction of its volume will project upwards if it floats in a liquid of density 1,020 km m^-3?
Solution:
Let V be the volume of the body
Volume inside water = V – \(\frac {V}{6}\)
= (1 – \(\frac {1}{6}\))V
= \(\frac {5}{6}\)V
Upward thrust in water = \(\frac {5}{6}\) × 1,000 × g N ……………..(i)
where density of water is 1,000 kg m^-3
Let υ be the volume of the body outside the liquid of density, 1,020 kg m^-3.
∴ Volume inside the liquid = (V – υ)
Upward thrust in liquid = (V – υ) × 1,020 × g N ……….(ii)
Upward thrust in two cases must be the same and must be equal to the weight of the body.

Very Short Answer Type Questions:

Question 1.
What is g on the moon as compared to that on earth?
Answer:
Nearly \(\frac {1}{6}\)th of its value on earth.

Question 2.
What is unit of G?
Answer:
It is Nm² kg^-2.

Question 3.
What is the mass of the earth?
Answer:
It is about 6 × 10²⁴ kg.

Question 4.
What is essential property of matter-mass or weight?
Answer:
Mass is the basic and essential property. It is constant everywhere. Weight of a body varies from place to place.

Question 5.
What is SI unit of weight of a body?
Answer:
It is newton (N).

Question 6.
The earth’s gravitational force causes an acceleration of 5 m s^-2 on a 1 kg mass somewhere in the space. How much will be the acceleration of a 3 kg mass at that place?
Answer:
Same i.e., 5ms^-2 since g at a place is independent of mass of the body.

Question 7.
Why one can jump higher on the surface of moon than on the earth?
Answer:
The g at moon surface is nearly 1/6th of that at the surface of earth. Hence one can jump six times higher on the moon with a given initial velocity.

Question 8.
Give the value of universal gravitational constant in S.I. units.
Answer:
(G) = 6.67 × 10^-11 Nm²/kg²
The value of gravitational constant.

Question 9.
The value of ‘G’ on the surface of earth is 6.67 × 10^-11 Nm²/kg². What is its value on the surface of moon?
Answer:
Since G is universal constant so its value on moon surface will be same as on the earth surface i.e. G = 6.67 × 10^-11 Nm²/kg² .

Question 10.
State two factors on which the gravitational force between two objects depends.
Answer:
The gravitational force between two objects depends on: (i) their masses (ii) distance between them.

Question 11.
Write the formula to find the magnitude of gravitational force between the earth and an object on the surface of the earth.
Answer:
F = \(\mathrm{G} \frac{\mathrm{Mm}}{r^{2}}\)

Question 12.
Can the mass of a body be zero.
Answer:
No, mass of body can never be zero.

Question 13.
Mass of an object on the earth is 600g. What will be its mass on moon?
Answer:
Mass of the object on moon will be same i.e. 600 g.

Question 14.
You find your mass to be 42 kg on a weighing machine. Is your mass more or less than 42 kg?
Answer:
Mass is a constant quantity. So, it can not be more or less than 42 kg.

Question 15.
How does the value of ‘g’ vary from equator to poles?
Answer:
The value of ‘g’ increases as we move from equator to poles.

Question 16.
What will be the weight of an object on the earth whose mass is 10 kg?
Answer:
Weight of the object on earth
(W) = m x g
= 10 kg × 10 m s^-2
= 100 N

Question 17.
Write the S.I. unit of G.
Answer:
Nm²/kg².

Question 18.
When does an object float when placed on the surface of water?
Answer:
If the density of object is less than water, it will float.

Question 19.
While swimming why do we feel light?
Answer:
The swimmer experiences an upward force by water, this causes buoyancy and makes the swimmer feel light.

Question 20.
Why does a truck or a motor-bus has much wider tyres?
Answer:
So that pressure acting on the road due to weight of truck or motor-bus may be small.

Question 21.
An army tank weighing more than a hundred tonne move conveniently on an earthen road. How?
Answer:
The army tank rests upon a continuous broad chain. So, the total surface area is large and pressure on road due to weight of tank is not very high.

Question 22.
What is the unit of relative density? Why?
Answer:
Relative density has no unit because it is a ratio of two terms having same units. So relative density is expressed in numbers only.

Question 23.
The weight of an object on the moon is ………………. of its weight on the earth.
Answer:
The weight of an object on the moon is 1/6th of its weight on the earth.

Punjab State Board PSEB 9th Class Science Important Questions Chapter 9 Force and Laws of Motion Important Questions and Answers.

PSEB 9th Class Science Important Questions Chapter 9 Force and Laws of Motion

Long Answer Type Questions:

Question 1.
What are the different types of Forces? Explain each with the help of example
Answer:
Types of forces. There are two types of forces:
1. Balanced forces
2. Unbalanced Forces.
1. Balanced Forces: When several forces are acting simultaneously on a body and their resultant is zero, the forces are said to be balanced forces.

In the case of balanced forces if some body is at rest then it will remain at rest and if it is moving with uniform speed then it will continue to move with the same speed, as if no force is doing any work. In this way with the effect of balanced forces. There does not take place any change in position of the body.

Balanced forces change the shape of the objects, e.g. if a rubber ball is pressed between palms by applying equal and opposite forces then the shape of the ball changes. This ball no longer remains round and instead becomes flat.

Example: In a tug of war, when both teams pull the rope with equal force, then resultant forces becomes zero. Therefore, both teams remain in their places. In this situation the forces applied by the two teams are equal and opposite so get balanced.
Condition for forces to be balanced.

Two equal forces acting in the opposite direction become balanced if they act along the same line and their magnitudes are equal.
Effect of Balanced Forces: Forces acting on any object if do not change its state of rest or its motion then these do change the shape of the object.

2. Unbalanced Forces: If the resultant of the several forces acting on a body is not zero, the forces are said to be unbalanced forces. Unbalanced forces produce change in the direction of uniform motion of the body or its state of rest.
Example:
In a tug-of-war, when one of the two teams pulls the rope with a larger force, it is able to pull the weaker team towards it. Here two forces are not balanced. Therefore, it results in the motion of the weaker team towards the larger force along the rope.

Question 2.
State and explain the Newton’s First Law of Motion.
Answer:
Newton’s First Law of Motion. This law states that “In this universe all bodies will remain in their state of rest or of uniform motion in a straight line until some external force is applied to bring about change in their state.
According to this law, motion can be divided into two parts:
1. First part says that a body at rest continues in its state of rest unless some external force is applied to bring change in its state of rest. We find a book lying on the table keeps lying in the same state unless someone applies force on it to pick it up.

2. Second part says that a body jn uniform motion continues moving in straight line path with a uniform speed unless someone applies external force to stop it. But in our daily life it appears but different.

As for example when we stop pedalling a bicycle the moving bicycle stops. After studying minutely it is found that between tyres of bicycle and ground there acts a force of friction which is an external force which opposes the motion. The resistance of air also opposes the motion of bicycle. So, moving bicycle stops moving due to these two forces.

Question 3.
What is inertia? What are its different types? Give examples for each one of them.
Answer:
Inertia: It is the property of matter by virtue ofivhich an object is unable to change by itself its state of rest or of uniform motion in a straight line.
Because of this property Newton’s First Law of Motion is also called the law of Inertia.

Types of Inertia Inertia is of three types:
1. Inertia of Rest: It means a body at rest tends to remain in its position of rest. i.e. a body at rest opposes the forces which try to move it. It can be understood clearly by the following example.
A man standing in a stationary bus or train falls backward when the bus or train suddenly starts moving forward. When the bus moves, the lower part (limbs) of his body begins to move along with the bus while his upper-part tends remain at rest due to inertia.

2. Inertia of Motion: This means a body in motion continues to move with uniform
motion in a straight line. i.e. it is the tendency of a body to remain in its state of uniform motion in a straight line.

Example: 1. A person sitting in moving bus falls forward when the moving bus suddenly stops. It is because as the bus stops the lower part of his body comes to rest along with the bus while upper part of his body continues to remain in motion due to inertia of motion.

2. An athelete runs for some distance before taking a jump so that his inertia of motion may help his muscular force to a longer jump.

3. Inertia of Direction. It is the property of a body which helps to maintain its direction i.e. it is inability of a body to change by itself its direction of motion.
Example: The mudguard is fitted in the wheel of a bicycle to protect from mud particles and water drops sticking to its wheel leaving it tangentially.
Imagine a stone tied to the end of a thread moving in a horizontal circle, while doing so, if the thread breaks then due to inertia of direction the stone flies off tangentially in a straight line.

Question 4.
State and explain Newton’s Second Law of motion with the help of this law how can we measure force.
Answer:
Newton’s Second Law of Motion. Newton’s second Law of motion helps to calculate the force required to bring a body in motion. It consists of two parts
1. The rate of change of momentum of a body is directly proportional to the applied unbalanced force and
2. the change in momentum due to the external applied force takes place in the direction of force.
i.e. According to this law “the external force applied in the body is directly proportional to the product of mass of the body and the acceleration produced in the direction of force.

Explanation: When a force acts on a body, it produces change in its momentum. If the force is doubled then the change in momentum also gets doubled. The more the force applied; the more is the change in momentum produced. Momentum is the product of mass of the body and its velocity. Generally no change in mass occurs. Therefore, the rate of change of momentum is actually the rate of change of velocity. Thus the applied force is proportional to the acceleration.

When an external force acts on a body at rest, it begins to move in the direction of force. When force acts in the direction of motion of the body then its momentum gets increased. But when force acts in a direction opposite to the direction of motion, its momentum gets reduced.
Force (F) ∝ mass (m) × acceleration (a)
or F = k × m × a ….(i)
(where k is a constant of proportionality)
If we choose the unit of force in such a way that as unit of force produces unit acceleration in a body of unit mass, then
Substituting F = 1, m = 1 and a = 1 in (1)
1 = k × 1 × 1
or k = 1
∴ from equation (i), F = 1 × m × a
or F = m × a
Force = Mass × Acceleration

Question 5.
Derive the mathematical relation for magnitude of force from Newton’s Second Law of Motion.
Answer:
Measurement of Magnitude of Force from Newton’s Law of Motion. Suppose force F acts on a body of mass’m’ for Y seconds which changes its velocity from u to υ, then
Initial momentum of body, p₁ = mu
Final momentum of body, p₁ = mυ
Now because final velocity (υ) is more than the initial velocity (u), therefore final momentum (p₂) will be more than the initial momentum (p₁) change in momentum,
p = p₂ – p₁
= mυ – mu
= m (υ – u)
According to second law of motion,

Question 6.
State and explain Newton’s third Law of motion.
Answer:
Newton’s third Law of Motion. This law states that “Every action has equal and opposite reaction” According to this law, there does not exist one force in isolation. Force always exists in pair i.e. forces of action and reaction always act on different bodies.

Explanation: (1) Consider two similar spring balances attached to each other through their hooks. One end of spring balance A is fastened to the fixed support. Pull the free end of spring balance B to right side. Note the readings of both the spring balances. Both will read the same as shown in fig. It is because read.
A and B pull each other in opposite direction with same force.

(2) Keep two balls A and B on a table at some distance from each other. When you push the ball. A towards B then the ball A acts on ball B. This force is represented by
F_A→B According to Newton’s third law of motion, the ball B also reacts and applies
force on ball A. This force is represented as F_B→A. if both the balls are similar then the magnitudes of action and reaction will be equal.
∴ F_A→B = – F_B→A
Action and reaction forces always act in the direction opposite to each other.

Question 7.
What is meant by the Law of Conservation of Momentum? Deduce this law mathematically with the help of Newton’s second and third law of motion.
Answer:
Law of Conservation of Momentum. For a system of bodies, the total vector sum of momenta of all the bodies due to mutual action and reaction remain unchanged so long as no external force acts on the system.”

Mathematical Derivation: Consider two rubber balls of masses m₁, m₂ and initial velocities u₁, u₂ respectively. Let these collide and their velocities after collisions be υ₁ and υ₂ respectively. If A applies a force F on B also for time t; B also applies a force F on A for same time t.
From Newton’s Second Law of Motion:

i.e. total momentum of balls A and B before collision
= Total momentum of balls A and B after collision
This proves the law of conservation of momentum that is the total momentum remains conserved.

Short Answer Type Questions:

Question 1.
What is force? Give its units.
Answer:
Force. Force is an agent which

• produces or tends to produce motion in the body
• stops the moving body or tends to stop
• increases the speed of the body or tries to increase the speed therefore,

Force may be defined is as physical cause (a push or a pull) which changes or tends to change the state of rest or uniform motion or direction of motion of a body. The force exerted by the engine makes the train to move from its actual position of rest while the force exerted by the brakes slows down or stops the moving train. The force exerted on the steering wheel of a car changes its direction of motion.
Force is a vector quantity.
Units of force: The unit of force depends upon the unit of mass and acceleration. S.I. unit of force is Newton and C.G.S. unit is Dyne
1N = 10⁵ Dynes

Question 2.
Why does the horse rider fall forward when a running horse suddenly stops?
Answer:
When horse is running, both the horse and the rider are in motion. When the horse suddenly stops, the lower part of the rider and horse come in the state of rest while the upper part of the rider remains in motion so that he falls forward.

Question 3.
When a horse suddenly gallops, the rider falls backward. Why?
Answer:
The horse and the rider form one system. Initially both are at rest. When the horse suddenly gallops then the horse and the lower part of the rider come into motion in the forward direction while the upper part of the rider’s body tends to remain at rest. Therefore, the rider falls backward.

Question 4.
Why does a passenger fall forwaid when he alights from the moving bus?
Answer:
While alighting from the moving bus the passenger falls forward because when the feet of the passenger touch the ground, his lower part suddenly comes to rest while the upper part still remains in motion. In this way the passenger falls forward.

Question 5.
Define momentum of a body. Also give its units.
Answer:
Momentum. It is defined as the quantity of motion possessed by the body. It is measured by the product of the mass and velocity of the body.

Question 6.
A fast-moving bullet when hits the windowpane makes a round hole while a stone strikes and shatters it, why?
Answer:
If stone piece strikes window pane glass, it gets shattered while a fast-moving bullet when strikes the windowpane a round hole is formed. The reason is that small particle of glass around and near the hole do not move due to inertia along with the bullet and threfore, do not scatter.

Question 7.
Explain how a dirty blanket becomes dust-free if it is jerked once or twice?
Answer:
If a dirty blanket is beaten with a stick or is given a jerk then dust particles get separated from it because when we beat or give a jerk to the blanket it comes in motion but due to inertia of rest, dust particles remained at rest and get separated and the blanket becomes dust-free.

Question 8.
Why a fan continues to rotate for sometime even after it is switched off?
Answer:
When a fan is rotating, then because of inertia of motion it continues it rotation for some time even if we switch if off. Due to friction on resistance of air it comes to rest after few seconds.

Question 9.
Why does a gun recoil when a bullet is fired from the gun? Explain.
Answer:
When bullet is not fired, then gun and bullet both are at rest, thus total momentum of both together is zero. When a bullet is fired from the gun the bullet moves with very high speed in the forward direction i.e. its momentum is very high. Now according to law of conservation of momentum, total momentum should still be zero as was before the firing of the bullet. Thus to balance the momentum of bullet in the forward direction gun recoil.

Question 10.
Why a cricket player lowers his hand while taking of catch of cricket ball?
Answer:
A lot of force is needed to stop a fast moving ball. If we lower our hands while catching the ball, acceleration of the ball is decreased and we have to apply less force of stop the ball.

Question 11.
Write differences between balanced and unbalanced forces.
Answer:
Differences between balanced forces and unbalanced forces:

Balanced forces	Unbalanced forces
1. When balanced forces act simultaneously on a body then their net resultant is zero.	When unbalanced forces act simultaneously on a body then their net resultant is not zero.
2. Balanced forces are acting on a body which is at rest, these can not bring it in motion.	Unbalanced forces act on a body at rest, these can bring it in motion.
3. These forces cannot bring a change in speed or direction of the motion.	This force can bring change in the speed of direction of motion.
4. This force can make a change in the shape of the body.	This force can not make a change in the shape of the body.

Question 12.
Why a boatman exists a force on water with his oars in the opposite direction to move forward?
Answer:
That force, which causes motion in any direction, is the reaction of the applied force. To move the boat in forward direction boatman exerts a force on water with his oars in the opposite direction. As a reaction to this force boat moves in forward direction because action and reaction are equal and opposite to each other.

Important Formulae:

1. Force (F) = m × a
2. Acceleration (a) = \(\frac {F}{m}\)
3. Acceleration (a) = \(\frac {υ – u}{t}\)
4. Momentum(p) = m × υ
5. Pressure (P) = \(\frac {F(force)}{A(Area)}\)

Numerical Problems (Solved):

Question 1.
What acceleration will be produced in a body of mass 3 kg, when a force of 12 N is applied?
Solution:
Here, Force (F) = 12 N
Mass (m) = 3 kg
Acceleration (a) =?
We know F = m × a
12 = 3 × a
or a = \(\frac {12}{3}\)
∴ a = 4 m s^-2

Question 2.
How much force will be required to produce an acceleration of 4 m s^-2 in a ball of mass 6 kg?
Solution:
Mass of the ball (m) = 6 kg
Acceleration produced in the ball (a) = 4ms^-2
Force (F) = ?
We know, F = m × a
= 6 × 4
Force (F) = 24 N

Question 3.
A man throws a ball of mass 0.5 kg vertically upwards with a velocity of 10 m s^-1. What will be its initial momentum? What would be its momentum at the highest point of its reach?
Solution:
Mass of the ball (m) = 0.5 kg
Initial velocity of ball (u) = 10 m s^-1
Final velocity of the ball (v) = 0 (At highest point the ball comes to rest)
Initial momentum of the ball = m × u
= 0.5 × 10
= 5 kg – m/s
Final momentunvof the ball = m × υ
= 0.5 × 0 = 0

Question 4.
A steam engine of mass 3 × 10⁴ kg pulls two wagons each of mass 2 × 10⁴ kg with an acceleration of 0.2 m s^-2. Neglecting frictional force, calculate the:
1. force exerted by the engine.
2. force experienced by each wagon.
Solution:
Mass of steam engine (m₁) = 3 × 10⁴ kg
Mass of two wagons (m₂) = 2 × (2 × 10⁴ kg)
Total mass of the engine and wagons (m) = m1 + m2
= 3 × 10⁴ + 4 × 10⁴
= (3 + 4) × 10⁴ kg
= 7 × 10⁴ kg
Acceleration (a) = 0.2 ms^-2
1. We know, F = m × a
= 7 × 10⁴ × 0.2
= 1.4 × 10⁴ N
2. Force experienced by each wagon = 1.4 × 10⁴ N

Question 5.
A bullet of mass 20 g moving with a speed of 500 ms^-1 strikes a wooden block of mass 1 kg and gets embedded in it. Find the speed with which block moves along with the bullet.
Solution:
Suppose the final velocity of the bag with bullet embedded in it is υ.
For Bullet, m₁ = 20 g = 0.02 kg, u₁ = 500 m s^-1, υ₁ = υ
For Block, m₂ = 1 kg, u₂ = 0, υ₂ = υ
According to the law of conservation of momentum,
Total momentum before collision = Total momentum after collision

Question 6.
A car travelling at the speed of 108 km/h takes 4 s to stop on applying brakes. Calculate the force acting on the car after applying brakes. Total mass of the car (including passengers) is 1000 kg.
Solution:
Inital velocity of the car (u) = 108 km/h
= 108 × \(\frac {5}{18}\)
= 30 ms^-1
Final velocity of the car (υ) = 0 ms^-1
Total mass of the car (m) = 1000kg
Time taken to stop the car (t) = 4s
Force ‘F’ due to application of brakes = m\(\frac {υ – u}{t}\)
= 1000kg × \(\frac {0 – 30}{4s}\)ms^-1
= – 750 kg – ms^-2
= – 750 N
Negative sign shows that the force applied by the brakes is acting in a direction opposite to the direction of motion of the car.

Question 7.
Which one requires more force, a body of mass 2 kg accelerated at the rate 5 m s^-2 or a body of mass 4 kg accelerated at 2 m s^-2
Solution:
Given:
m₁ = 2kg, a₁ = 5 ms^-2
m₂ = 4kg, a₂ = 2 ms^-2
Force required for first body, F₁ = m₁ × a₁
= 2kg × 5ms^-2
Force required for second body, F₂ = m₂ × a₂
= 4kg × 2ms^-2 = 8N
F₁ > F₂
From this, it is clear that the first body would require more force.

Question 8.
A bullet of mass 0.03 kg is fired from a gun of mass 3 kg which leaves the muzzle of the gun write a velocity of 100 ms^-1. If bullet takes 0.003 s to come out of the gun then calculate the force acting on the gun.
Solution:
Mass of the gun (m₁) = 3 kg
Mass of the bullet (m₂) = 0.03 kg
Before firing, both the gun and the bullet are at rest
∴ Initial velocity of the gun (u₁) = 0
Initial velocity of the bullet (u₂) = 0
After firing. Final velocity of the gun (υ₁) =?
Final velocity of the bullet (υ₂) = 100 m s^-1
According to the law of conservation of momentum

Negative sign shows that the gun moves backward and experiences a force of 1000 N

Question 9.
From a rifle of mass 5000 g a bullet of 20 g is fired with a velocity of 500 ms^-1 with respect to the ground. Find the velocity of recoil of the rifle.
Solution:
According to law of conservation of momentum,
MV + mυ = 0
V = – \(\frac {mυ}{M}\)
Now m = 0.02 kg, υ = 500 ms^-1 and M = 5 kg
∴ \(\frac {20×500}{5000}\)
or V = – 2ms^-1
Negative sign shows recoiling of the rifle.

Question 10.
A girl of 40 kg mass jumps with a horizontal velocity of 5 ms^-1 on a stationary trolley. The wheels of the skate are frictionless. What will be the velocity of the girl in the position of start of the trolley. Suppose no unbalanced force is acting in the horizontal direction.
Solution:
Suppose in the initial motion of the trolley, the velocity of the trolley and the girl is υ
Total initial momentum of the girl and trolley = 40 kg × 5 m s^-1 + 3 kg × 0 ms^-1
= 200 kg ms^-1 + 0
= 200 kg – ms^-1
Total momentum of the girl and trolley after she jumps on the trolley.
= 40 kg × υ ms^-1 + 3 kg × υ m s^-1
= (40 + 3) × υ kg – ms^-1
= 43 υ kg – ms^-1
According to the law of conservation of momentum.
43υ = 200
υ = \(\frac {200}{43}\)
= 4.65 ms^-1
The girl boarding on the trolley will move with a velocity of 4.65 m s^-1 in the direction of jump.

Question 11.
The following is the distance-time table of an object in motion.

Time in seconds	Distance in metres
0	0
1	1
2	8
3	27
4	64
5	125
6	216
7	343

(a) What conclusion can you draw about acceleration? Is it constant, increasing, decreasing or zero?
(b) What do vou infer about forces acting on obiect?
Solution:

(a) Table shows that the motion is accelerated and acceleration is increasing uniformly with time i.e. acceleration is increasing by 6 ms^-2 every second.
(b) Since acceleration is increasing uniformly, the force is also increasing uniformly with time.

Question 12.
Two persons manage to push a motor car of mass 1,200 kg at uniform velocity on the road. The same motor can be pushed by three persons to produce an acceleration of 0.2 ms^-2. With what force does each person push the motor car? Assume that all persons push motor car with same muscular effort.
Solution:
Here, mass of the car (m) = 1200 kg
Acceleration produced in the car (a) = 0.2 ms^-2
Acceleration produced by first two persons in the car = 0
It is clear that when third person pushes the car, an unbalanced force acts on the car which produces an acceleration of 0.2 ms^-2
∴ Force applied by three persons together (F) = m × a
= 1200 × 0.2 = 240 N
Now because three persons together push the car using their muscular force to produce an acceleration of 0.2 ms^-2
∴ Push (Force) applied by each person = \(\frac{F}{3}\)
= \(\frac{240 \mathrm{~N}}{3}\)
= 80 N

Question 13.
A hammer of mass 500 g moving at 50 ms^-1, strikes a nail. The nail stops the hammer in a very short time of 0.01 s. What is the force of the nail on the hammer?
Solution:
Mass of the hammer (m) = 50 gm
= \(\frac{500}{1000}\)kg
= \(\frac{1}{2}\)kg
Initial velocity (u) = 50ms^-1
Final velocity (v) = 0ms^-1
Time (t) = 0.01s
Force (F) = ?
We know, υ = u + at
0 = 50 + a × 0.01
– 50 = a × \(\frac{1}{100}\)
a = – 50 × 100
∴ a = – 5000 ms^-2
Here, negative sign indicates that there is retardation.
Now force applied by the nail on the hammer (F) = m × a
= \(\frac{1}{2}\) × (- 5000)
= – 2500 N
∴ Force = 2500 N

Question 14.
A motorcar of mass 1,200 kg is moving along a straight line with uniform velocity of 90 km h^-1. Its velocity is slowed down to 18 km h^-1 in 4 s by an unbalanced external force. Calculate the acceleration and change in momentum. Also calculate the magnitude of the force required.
Solution:
Here, mass of the car (m) = 1200 kg
Time (t) = 4 s
Initial velocity of the car (u) = 90 km/h
= \(\frac{90 \times 5}{18}\)ms^-1
= 25ms^-1
Final velocity of the car (υ) = 18 km/h
= 18 × \(\frac{5}{18}\)ms^-1 = 5ms^-1
Acceleration of the car (a) = ?
Change in momentum of the car = ?
Magnitude of the force acting on the car (F) = ?
We know, υ = u + at
5 = 25 + a × 4
– 20 = 4a
or a = \(\frac{20}{4}\)
Initial momentum = mu = 1,200 × 25 = 30,000kg ms^-1
Final momentum = 1,200 × 5 = 6,000kg ms^-1
Change in momentum = Final momentum – Initial momentum
= mυ – mu
= m × (υ – u)
= 1200 × (5 – 25)
= 1200 × (- 20)
= – 24000 kg ms^-1
= 24000kg – ms^-1 (decrease)
F = \(\frac{m×(υ – u)}{t}\)
= \(\frac{1,200×(5 – 25)}{4}\)
F = – 6,000 N
Magnitude of the force (F) = 6000N

Very Short Answer Type Questions:

Question 1.
To bring a body into motion, what is required to be done?
Answer:
It is required to be pulled, pushed or kicked.

Question 2.
Why does an object fall down?
Answer:
Due to unbalanced gravitational force.

Question 3.
Which type of force is required to change the direction of motion of the body – a balanced or unbalanced force?
Answer:
An unbalanced force is required.

Question 4.
Why does a body stop after rolling down for some time?
Answer:
Due to frictional force.

Question 5.
How can force of friction be reduced?
Answer:
By polishing/smearing the surface with a lubricant.

Question 6.
Which scientist postulated the three laws of motion?
Answer:
Newton.

Question 7.
By which other name the first law of motion is known?
Answer:
Law of Inertia.

Question 8.
Of heavy and light objects, which have more inertia?
Answer:
Heavier objects have more inertia.

Question 9.
What is the S.I unit of momentum?
Answer:
The S.I. unit of momentum is kg – ms^-1.

Question 10.
Why is talcom powder sprinkled on carrom board while playing?
Answer:
In order to reduce friction.

Question 11.
Why does an athelete run before taking a high jump?
Answer:
To increase inertia in order to take high leap.

Question 12.
What is law of conservation of momentum?
Answer:
Law of conservation of momentum. The sum total of momentum of two objects before and after collision remains same unless some external force is applied.

Question 13.
A bus and a ball are moving with the same speed. To stop which one would require more force?
Answer:
Due to more inertia of bus, more force is required to be applied for stopping it.

Question 14.
A vehicle stops on applying brakes. During this activity, what happens to its momentum?
Answer:
In this activity the major part of momentum of the vehicle is transferred to the ground while the remaining part is transferred to the air molecules.

Question 15.
1 kg wt is equal to how many newtons?
Answer:
1 kg wt = 9.8 Newtons.

Question 16.
1 newton is equal to how many kg wt?
Answer:
1 newton = 0.102 kg wt.

Question 17.
On which physical quantity inertia of an object depends?
Answer:
On mass of the object.

Question 18.
On which Newton’s law of motion, the working principle of rocket is based?
Answer:
On Newton’s third law of motion.

Punjab State Board PSEB 9th Class Science Important Questions Chapter 8 Motion Important Questions and Answers.

PSEB 9th Class Science Important Questions Chapter 8 Motion

Long Answer Type Questions:

Question 1.
Derive mathematically the equations of motion.
Answer:
Equations of motion under uniform acceleration: The following are the equations of motion of an object moving in a straight line with uniform acceleration.
1. υ = u + at
2. S = ut + \(\frac{1}{2}\)at²
3. υ² – u² = 2aS
1. First Equation of Motion, υ = u + at
Let u be the initial velocity and ‘a’ be the uniform acceleration of a body in motion so that after every 1 sec its velocity increases by ‘a’.
Increase in velocity of the body after 1 sec = a
Secondary Increase in velocity of the body after 2 sec = a + a = 2 a
∴ Increase in velocity after t sec = a × t = at
Therefore, velocity of an object after t secs = Initial velocity + increase in velocity of the object after ‘t’ secs
or υ = u + at

2. Second equation of motion S = ut + \(\frac{1}{2}\)at²
Let ‘u’ be the initial velocity of the body in motion having uniform acceleration ‘a’ and after ‘t’ second the final velocity be ‘υ’.
∴ Increase in velocity of the body after 1sec = a
Velocity of the body after 1 sec from start of its motion = (u + a)
Velocity of the body 1 second before the end of its motion = (υ – a)

Question 2.
For uniform accelerated motion, draw by graphical method establish the following equations of motion:
1. υ = u + at
2. S = ut + \(\frac{1}{2}\)at²
3. υ² = u² + 2aS
Answer:
Consider an object moving with initial velocity ‘u’ along a straight line and uniform acceleration ‘a’. Suppose its final velocity becomes υ after time t and during this time it travels a distance S. If time is represented along X-axis and velocity along Y-axis, then velocity-time graph obtained will be BA, an ipchned straight line. With its help we can derive the various equators of motion.
Here OA = ED = u,
OC = EB = υ and OE = t = AD
(a)Equation for velocity-time relation. We know that
Acceleration = Slope of velocity-time graph AB or

This proves the first equation of motion.

(b) Equation for position-time relation
We know that area below velocity-time graph and time axis gives the distance covered by the body.

(S = ut + \(\frac{1}{2}\)at²)
Distance travelled by the object in time t is
S = Area of the trapezium OABE
= Area of rectangle OADE + Area of triangle ADB
= OA × OE + \(\frac{1}{2}\)DB × AD
a = \(\frac{\mathrm{DB}}{\mathrm{AD}}=\frac{\mathrm{DB}}{t}\)
or DB = at
= u × t + \(\frac{1}{2}\)at × t
or S = ut + \(\frac{1}{2}\)at²
This proves the second equation of motion.

(c) Equation for position-velocity relation (υ² – u² = 2aS).
The distance travelled by object in time t is:
S = Area of trapezium OABE
= \(\frac{1}{2}\)(EB + OA) × OE
= \(\frac{1}{2}\)(EB + ED) × OE …….. (1)

Question 3.
Draw velocity-time graph for a body moving with uniform velocity. Hence show that the area under the velocity-time graph gives the distance travelled by the body in a given time interval.
Answer:
Distance covered as area under the velocity-time graph. In Fig. straight line PQ is the velocity-time graph of a body moving with a uniform velocity, ‘υ’ represented by OP.

Area of rectangle ABCD
= AD × AB
= OP × AB
= υ × (t₂ – t₁)
= Velocity × time
= Distance travelled in time interval (t₂ – t₁)
Hence, the area under the velocity-time graph gives the distance travelled by the body in the given time interval.

Question 4.
What is meant by Angular velocity? How is it related to linear velocity? Derive the relation.
Answer:
Angular velocity: The angle traced out by a body moving along a circular path in unit time is called Angular velocity. It is usually represented by a greek letter ω (omega). If θ is the angle covered by a body in time ‘t’, then
Angular velocity (ω) = \(\frac{Angle traced out by the moving body(θ)}{t}\)
∴ ω = \(\frac{θ}{t}\)
or θ = ωt

Relation between Linear velocity and Angular velocity:
Suppose a body in motion in a circular path of radius ‘r’ having linear velocity υ. Suppose ‘S’ is the linear distance covered by the body in time ‘t’ and relative to this, ‘θ’ is the angular displacement produced, then

Short Answer Type Questions:

Question 1.
Define rest and motion. Give one example for each.
Answer:

• Rest: A body is said to be at rest if it does not change its position with respect to its surroundings. A book lying on the table in a room is at rest with respect to the other objects in the room.
• Motion: A body is said to be in motion if it changes its position with time with respect to its surroundings. A car running on the road is in motion with respect to the electricpole, trees along the roadside.

Question 2.
Show that rest and motion are relative terms.
Or
Can an object be af rest as well as in motion at the same time?
Answer:
An object may be at rest relative to one surrounding object and at the same time it may be in motion with respect to some other object. For example, a passenger sitting in moving train is at rest relative to other co-passengers. But since he is sharing the motion of the train, so he is in motion relative to the outside trees, lamp posts etc. Thus, rest and motion are relative terms.

Question 3.
Give some points of differences between distance and displacement.
Or
Give two differences between distance and displacement.
Answer:
Differences between distance and displacement:

Distance	Displacement
1. Distance is the length of the actual path covered by a body, irrespective of its direction of motion.	Displacement is the shortest distance between the initial and final positions of a body in a given direction.
2. Distance between two given points may be same or different for different paths chosen.	Displacement between two given points is always same.
3. It is a scalar quantity.	It is a vector quantity.
4. Distance covered is always positive or zero.	Displacement covered may be positive, negative or zero.

Question 4.
What is meant by uniform motion?Give an example.
Answer:
Uniform motion. If an object covers equal distances in equal intervals of time, hoxvever small the time interval may be, then the motion of the object is said to be uniform motion. For example, suppose a bus moves 10 km in the first 15 minutes, 10 km in second 15 minutes, 10 km in third 15 minutes and so on. Then one can say that the bus is in uniform motion.

Question 5.
Define the term velocity. What is its SI unit?Is it a scalar or vector quantity?
Answer:
Velocity: Velocity of a body is defined as the displacement produced per unit time. It is also defined as the speed of a body in a given direction.
Velocity = Displacement/Time
If ‘S’ is the distance travelled by a body in a given direction and t is the time taken to travel that distance, then the velocity ‘υ’ is given by
υ = \(\frac{S}{t}\)
The SI unit of velocity is m s^-1.
Velocity is a vector quantity because it requires both magnitude and direction for its complete description.

Symbols of Physical Quantities and Important Formulae:

(A) Symbols of Physical Quantities

• Time = t
• Speed = v
• Distance = S
• Initial Velocity = u
• Final Velocity = v
• Acceleration = a
• Average Velocity = V_av

(B) Important Formulae:

If initial velocity u at time t velocity υ and uniform acceleration a Then the under given relations are called Equations motion:
υ = u + at (Velocity at time t)
S = ut + \(\frac{1}{2}\)at²(Displacement in time ‘t’)
υ² = u² + 2aS (Velocity square relation)
Displacement in n th The Second of time (S_n) = u + (2n – 1)

Numerical Problems (Solved):

Question 1.
A police car running on a highway with a speed of 30 km/h fires on the vehicle of thiefs running in the same direction at a speed of 192 km/h. If the velocity of the bullet is 150 m/s then with what velocity the bullet will hit the thiefs?
Solution:
Velocity of the bullet fired = 150 m/s
= 150 × \(\frac{18}{5}\)km/h = 540 km/h
∴ Total speed = Speed of police vehicle + Speed of bullet
= 30 km/h + 540 km/h = 570 km/h
Speed of the bullet relative to the speed of thief’s vehicle in the same direction
= (570 – 192) km/h
= 378 km/h
= \(\frac{378 \times 1000}{60 \times 60}\) m/s
= 105 m/s

Question 2.
A train 50 m long travels on a plain and level track and reached a post in 5 secs. Find
1. speed of the train
2. the time train will take to cross 450 m long bridge.
Solution:
1. Since the train takes 5 secs to reach the post, it covers a distance equal to its own length, then
speed of train = \(\frac{Total distanve travelled}{Total time taken}\)
= \(\frac{50m}{5s}\)
= 10 m/s

2. Distance travelled by the train to cross the bridge
= Length of the bridge + Length of train
= 450 m + 50 m
= 500 m

∴ Time taken to cross the bridge = \(\frac{Total distance covered}{speed of the train}\)
= \(\frac{500m}{10m/s}\)
= 50 s

Question 3.
A cheetah is the fastest land animal and can achieve a peak velocity of 100 km/h upto distances less than 500 m. If a cheetah spots his prey at a distance of 100 m. What is the minimum time it will take to get its prey, if the average velocity attained by it is 90 km/h.
Solution:
Here, υ = 90 km/h
= \(\frac{90 \times 1000 \mathrm{~m}}{3600 \mathrm{~s}}\)
= 25 m/s
s = 100m
Minimum time, t = \(\frac{s}{υ}\)
= \(\frac{100}{25}\) = 4s.

Question 4.
A car travels a certain distance with a speed of 50 km/h and returns with a speed of 40 km/h. Calculate the average speed for the whole journey.
Solution:
Let the one-way distance = x km

Question 5.
On a 100 km track, a train travels the first 30 km at a uniform speed of 30 km h^-1. How fast must the train travel the next 70 km so as to average 40 km h^-1 for the entire trip?
solution:

Question 6.
A railway train 50 m long passes over a bridge 250 m long with uniform velocity of 10 m s^-1. How long will it take to completely, pass over the bridge?
Solution:

To completely pass over the bridge, the train will have to cover the length of the bridge, as well as its own length i.e., AB + BC
∴ Total distance to be covered, S = 50 + 250 = 300 m
Velocity of train, u = 10 m s^-1
Here velocity is uniform, hence
a = 0 m s^-2
Using S = ut + \(\frac{1}{2}\)at²
300 = 10t + 0
or t = 30 s
Hence train will pass completely over the bridge in 30 s.

Question 7.
A car starts from rest and moves with uniform acceleration for 40 s. It then moves with uniform velocity attained by it and is finally brought to rest in 30 s under uniform retardation. The car covers a total distance of 1,380 m in 2.5 min. Calculate constant speed, acceleration and retardation.
Solution:
Let x be the constant speed. Now the total distance covered is equal to total area between velocity-time graph and time axis. Therefore
Distance covered = area of ∆ABC + area of rectangle BCDE + area of ADEF

Question 8.
The graph shown in Fig. indicates the position of body at different positions. Calculate the speed of the body as it moves from (i) A to B; (ii) B to C and (iii) C to D.
Solution:

Speed from A to B = Slope of AB
= \(\frac{\mathrm{BF}}{\mathrm{AF}}=\frac{3-0}{5-2}\) = 1ms^-1
(ii) Speed from B to C is zero since slope of BC is zero. From B to C, the body is at rest.
(iii) Speed between C and D = Slope of CD
= \(\frac{D G}{C G}=\frac{7-3}{9-7}\)
= \(\frac{4}{2}\) = 2ms^-1

Very Short Answer Type Questions:

Question 1.
What is motion?
Answer:
Motion: When an object changes its position with time then it is said to be in motion.

Question 2.
What is displacement of object?
Answer:
Displacement. The change in position of an object in a given direction is known as displacement. It is measured by the shortest distance moved by an object from its initial position to final position.

Question 3.
Which device shows the speed of vehicles?
Answer:
Odometer.

Question 4.
What is uniform motion?
Answer:
Uniform motion. When a body covers equal distances in equal intervals of time then its motion is called uniform motion.

Question 5.
Give two examples of non-uniform motion.
Answer:
1. A car moving on the road.
2. A man doing exercise in park.

Question 6.
Define speed.
Answer:
Speed. The distance travelled by a body in a unit time is called its speed.

Question 7.
What is the SI unit of speed?
Answer:
S.I. unit of speed is ms^-1.

Question 8.
How is average speed obtained?
Answer:
Average speed. It is the total distance travelled by an object divided by the time taken to travel that distance.
Average Speed = \(\frac{Total distance travelled}{Total time taken}\)

Question 9.
What is velocity?
Answer:
Velocity: The speed in a particular direction is called velocity.
Or
It is the distance travelled by an object in a particular direction.

Question 10.
What is acceleration?
Answer:
Acceleration. It is defined as the rate of change of velocity with time.
Acceleration = \(\frac{Change of velocity}{Total time taken}\)

Question 11.
What is the SI unit of acceleration?
Answer:
ms^-2

Question 12.
A cricket player tosses the ball upward and again catches it. What is the total displacement?
Answer:
Total displacement is zero.

Question 13.
Is displacement a scalar or vector quantity?
Answer:
Displacement is a vector quantity because it needs both magnitude and direction for its complete representation.

Question 14.
What would be acceleration of a body if its velocity-time graph is line parallel to the time axis?
Answer:
Zero, as the body possesses uniform velocity.

Question 15.
A body is moving along the boundary of a square plot of land with constant speed. Does its velocity remain unchanged?
Answer:
No. because its velocity changes due to change in direction.

Question 16.
What will be the position-time graph of a city bus standing at rest at a depot?
Answer:
A straight line parallel to the time axis.

Question 17.
What is the nature of the distance-time graph for an object moving uniformly along a straight long road?
Answer:
A straight line inclined to the time axis.

Question 18.
Does the speedometer of a car measure its average speed?
Answer:
No. It measures only instantaneous speed.

Punjab State Board PSEB 9th Class Science Important Questions Chapter 7 Diversity in Living Organisms Important Questions and Answers.

PSEB 9th Class Science Important Questions Chapter 7 Diversity in Living Organisms

Long Answer Type Questions:

Question 1.
Give a broad outline classification of kingdom plantae.
Answer:
Classification of kingdom Plantae:

1. Kingdom Plantae is divided into five subdivisions i.e. Thallophyta, Bryophyta, Pteridophyta, Gymnosperms and Angiosperms.
2. Thallophyta includes Algae.
3. Algae are found in water and moist places.
4. Fungi are non-green, heterotrophic (parasitic and saprophytic) thallophytes.
5. In Bryophytes, plant body is thallus-like (thalloid) or leaf-like (foliose). Body differentiated to form stem and leaf-like structure. Riccia, Marchantia and Funaria are examples.
6. In pteridophytes plant body is differentiated into root, stem and leaves. There is specialised tissue for conduction of water and other materials. This group includes Marselia, Ferns, and horse tails.
7. In Gymnosperms, seeds are not covered with fruit wall or pericarp. Cycas, Pine, and deodar are examples.
8. In Angiosperms, seeds are covered with fruit wall or pericarp to form fruits.

Question 2.
What are phanerogams? Write characters of gymnosperms and angiosperms.
Answer:
Phanerogamae. These are seed-bearing plants. Vascular tissue is present. They are found on land. This division is composed of two main sub-divisions i.e. Gymnosperms and Angiosperms.

Characters of gymnosperms:

1. They are flowering plants and seeds develop inside fruit.
2. Cotyledons are the plant embryos present inside the seed.
3. Plant body is divided into root system and shoot system. Examples: Mango, Rose, Wheat, Grasses.

Question 3.
Give an outline classification of animal kingdom with two characters of each phylum with example.
Answer:
Classification of kingdom Animalia:

Name of phylum	Characters	Examples
1. Porifera	Pore bearing body, spongocoel present.	Leucosolenia, Sycon, Spongilla
2. Coelenterata	Diploblastic, radial symmetry, nematocysts present.	Hydra, Obelia, Physalia, Aurelia
3. Platyhelminthes	Triploblastic, flat body, acoelomate	Fasciola, Taenia, Turbellaria
4. Nematehelminthes	Pseudocoelomate, cylindrical body	Ascaris, Dracunculus
5. Annelida	coelomate, segmented body, setae or suckers or parapodia present.	Pheretima, Nereis, Leech
6. Arthropoda	Jointed appendages, chitinous exoskeleton, haemocoel present	Crab, prawn, centipede, spider, cockroach
7. Mollusca	soft-bodied, shell present	Pila, Unio, Chiton, Dentalium
8. Echinodermata	spiny skin, water vascular system	Sea Lily, Seastar, Sea urchin, Sea cucumber
9. Hemichordata	Notochord in proboscis, Tomaria larva	Balanoglossus
10. Chordata	Notochord present, dorsal hollow nerve tube, pharynx perforated by gill slits	Fishes, Frog, Toad, Snakes, Lizard, Birds, Mammals

Question 4.
Write characters of phylum protozoa and phylum porifera.
Answer:
Characters of Phylum Protozoa:
1. Very minute, one-celled microscopic organisms. Cell itself is an organism therefore, they are also called acellular organisms.
2. Structure is very simple. The body consists merely of a mass of protoplasm. There is no tissue or organ formation.
3. Generally, there is no skeleton. However, locomotory and feeding organelles such as pseudopodia, flagella or cilia may be present.
Example. Amoeba, Entamoeba, Paramecium, Trypanosoma.

Characters of Phylum Porifera:
1. They are primitive, sessile animals with specialized cells but no tissues or organs.
2. Pores ali over the body, no digestive tract.
3. Collar cells filter out food particles from water current flowing through canal system.
4. Mostly marine.
5. They are called sponges.
Examples: Euplectella, Sycon, Spongilla.

Question 5.
Give a brief account of Whittaker’s five kingdoms of life.
Answer:
Whittaker’s Five Kingdoms are: Monera, Protista, Fungi, Plantae and Animalia.

1. Kingdom Monera: Monerans are prokaryotes. Examples: Bacteria, Blue-green algae.
2. Kingdom Protista: Protists are unicellular eukaryotes having widely diverse lifestyles. Protists form tine precursors from which higher forms-Plantae, Fungi and Animalia-arose on photosynthetic, assimilative and ingestive lines. Examples: Mastigophores, Ciliates, Sarcodines, Sporozoans, Slime moulds, Diatoms.
3. Kingdom Fungi: Fungi are eukaryotic, heterotrophic organisms with assimilative nutrition. Examples: Rhizopus, Agarieus,
4. Kingdom Plantae: Plantae includes eukaryotic, multicellular, photosynthetic organisms. It includes green multicellular plants.
5. Kingdom Animalia: Animals are eukaryotic, multicellular consumer characterised by ingestive nutrition. It includes non-chordates and chordates.

Question 6.
Differentiate between plants and animals.
Answer:
Differences between plants and animals:

Characters	Plants	Animals
1. Mode of nutrition	Autotrophs, prepare food from inorganic substances.	Heterotrophs, feed on com­plex organic compounds.
2. Photosynthesis	Photosynthesize.	Do not photosynthesize.
3. Chlorophyll	Possess chlorophyll.	Have no chlorophyll.
4. Locomotion	Are fixed but move parts of the body.	Move the whole body.
5. Branching	Branching body.	Compact body.
6. Response	Are less sensitive and respond slowly.	Are highly sensitive and re­spond quickly.
7. Cell wall	Cellulose cell walls usually present.	Have no cellulose cell walls.

Question 7.
Enlist the peculiar features of phylum Arthropoda.
Answer:

1. These have organ-system organization and bilateral symmetry.
2. These are triploblastic and haemocoelomates (have hemocoel-a body cavity with blood).
3. Their body is externally covered by a sclerotized chitinous exoskeleton formed of plates, called sclerites, and are formed of chitin.
4. Body is divided into 2 (cephalothorax and abdomen) or 3 parts (head, thorax and abdomen).
5. Mouth is surrounded by mouthparts which are of different types in different arthropods.
6. These have jointed appendages which are of different types to perform different functions.
7. These have complete and coiled gut.
8. Respiration occurs by gills or book lungs or tracheae (air tubes).
9. Blood is colourless and is called hemolymph.
10. Excretion occurs by green glands or coxal glands or malpighian tubules.
11. Examples: Insects Periplaneta (cockroach), Butterfly, Dragonfly, Housefly, Crustaceans, Crab, Centipede, Palaemon (Prawn), Millipede and Scorpion (Arachnid).

Question 8.
Write distinct features of phylum Echinodermata.
Answer:

1. Spiny skin of these animals contain dermal calcareous plates. Spines may be movable (c.g. sea urchin).
2. Pentaradial symmetry in adult but larva is bilaterally symmetrical.
3. Head absent. But divisible into central disc and arms.
4. Water vascular system (Ambulacra! system) is present. It consists of an array of radiating and tube-like appendages called tube feet. Locomotory organs are tubular tube feet or podia and also aid in capturing prey.
5. Body has oral surface bearing mouth and aboral surface bears anus.
6. Tube feel, and dermal branchiae aid in gaseous exchange.
7. All are marine, mostly gregarious and free living, creep slowly on the sea bottom.
   Examples: Star fish, Sea urchin. Sea cake, Sea lily and Sea cucumber.

Question 9.
Give diagnostic characters of phylum chordata.
Answer:
Diagnostic characters of Phylum Chordata:

1. Presence of notochord, at any stage of life history. Notochord is stiff rod-like structure which is retained throughout life in lower chordates. It is replaced by vertebral column in higher chordates.
2. Presence of dorsal, hollow nervous system.
3. Pharynx is perforated by gill slits at any stage of life history.
4. Tail is present at any stage of life history.
5. Respiratory pigment haemoglobin is present in the R.B.C.

Short Answer Type Questions:

Question 1.
Briefly describe diversity of life.
Answer:
Diversity of life (also called biological diversity or biodiversity) is the variety of living systems. It may refer to extinct organisms, but also to their diversity in the past. It usually covers multiple levels of biological diversity. About 2 million species have been described upto date. About 17000 – 19000 new species are added every year to the list. Exact number of species present on earth is unknown, current estimates favouring figures in the range of 8-12 million.

Thus biological diversity includes all forms of life including micro-organisms, plants and animals. Biological diversity is constantly changing.

Question 2.
Differentiate taxonomy and systematics.
Answer:
Difference between Taxonomy and Systematics:

Taxonomy	Systematics
1. It is the science of identification, nomenclature and classification. 2. It deals with rules and principles of classification.	1. Systematics is the science of identification, nomenclature, description and classification. 2. It brings out unique properties at every level of classification

Question 3.
Describe the importance of classification.
Answer:
Importance of classification:

1. Recognition: Classification of living beings recognises the basic taxonomic units or species.
2. Description: Classification of organisms is responsible for description of species.
3. Relationship: It tells a possible way for grouping these units on the basis of their resemblances and relationships.
4. Phylogeny: It gives us most of the information permitting a reconstruction of phylogeny of life. It helps in understanding the evolution of organisms.
5. Applied biology: It has great role in applied biology (agriculture, public health, environmental biology) also.
6. The introduction of harmful plants and animals can be checked. Exact identification of harmful pests, a disease vector, a pathogen and their control is made possible with knowledge of applied biology.
7. Human health: Exact identification of insects helps in controlling the epidemic diseases like malaria, filaria, dengue fever, kala-azar etc.
8. Horticulture: Several ornamentals have been introduced due to proper identification and nomenclature.

Question 4.
Why are local names not sufficient to recognize the organisms? What are the advantages of keeping scientific names?
Answer:
Local names are not understood elsewhere. The common name of a species often varies with language and region of world. In Biology, we deal with a very large number of species. It would not be possible to refer to them unless each one of them had a separate name for itself.
Advantages of scientific names:

1. The scientific names are same all over the world.
2. They are uniformly binomial.
3. They are definite and accepted universally.
4. They are descriptive.
5. They indicate general relationship.

Question 5.
Write different categories of classification.
Answer:

1. Species: It is defined as a dynamic group of organisms, which:
   • resemble each other in all essential respects, i.c. structure and function.
   • Interbreed among themselves to produce fertile young ones of their own kind.
2. Genus: It forms the taxonomic higher category than species. It is a group of closely related species.
3. Family: A number of genera having several common characters constitute a family.
4. Order: A number of families having many common characters are placed in an order.
5. Class: The class is the basic category. Similar orders are grouped together in the common class. A class is generally a subdivision of a phylum.
6. Phylum: A number of classes having common features constitute a phylum.
7. Division: In the case of plants, many classes constitute a division which corresponds to the phylum of animal kingdom.
8. Kingdom: All the animals are included in Kingdom Animalia, while all plants are included in the Kingdom Plantae. It is the highest taxonomic category.

Question 6.
Classify tiger and mango.
Answer:

Category	Tiger	Mango
Kingdom	Animalia	Plantae
Phylum/Division	Chordata	Tracheophyta
Sub-Phylum	Vertebrata	—
Class	Mammalia	Mangoliopsida
Order	Carnivora	Spindales
Genus	Panther a	Mangifera
Species	Tigris	Indica

Question 7.
List differences between monocot plants and dicot plants.
Answer:
Apart   below:

Monocot plants	Dicot plants
1. Roots are generally adventitious.	1. They usually possess tap root.
2. Venation in leaves is parallel.	2. Venation is reticulate.
3. Flowers of monocots are trimerous i.e. floral leaves in each whorl are either three or a multiple of three.	3. Flowers in dicots are either tetramerous or pentamerous.
4. The calyx and corolla are not differentiated and the outer two whorls are exactly alike to form perianth.	4. The flower has distinct calyx and corolla.
5. Vascular bundles in stem are scattered and closed.	5. The vascular bundles in dicot stem arranged in-ring and are open.

Question 8.
What are the basis of Whittaker’s system of classification?
Answer:
Whittaker based his classification on the following three criteria:

1. The prokaryotic versus eukaryotic structure of cell.
2. The unicellular versus multicellular organization.
3. The three different modes of nutrition i.e. autotrophic, absorptive and holozoic (ingestive).

Question 9.
What are the advantages of five-kingdom system of classification?
Answer:
Advantages of five-kingdom system:

1. The subdivisions of two kingdoms have been redistributed among additional kingdoms. Such an arrangement reflects the phylogeny evolutionary history of different life styles in a better way.
2. This system allows us to visualize the increase of complexity with evolutionary time.
3. Five kingdom arrangement allows us to visualize the divergence of their modes of nutrition in the multicellular organisms.
4. An added advantage of Whittaker’s system lies in the coherence and definable characters of a kingdom as a unit of classification.

Question 10.
Name the five kingdoms as proposed by R.H. Whittaker. Give at least one example in each case.
Answer:
Robert H. Whittaker of Cornell University organised the living organisms into five kingdoms as follows:

1. Kingdom Monera (Bacteria, Blue-green algae)
2. Kingdom Protista (Amoeba, Euglena)
3. Kingdom Fungi (Mushroom)
4. Kingdom Plantae (Green Plants)
5. Kingdom Animalia (Animals)

Question 11.
Give general characters of kingdom Monera.
Answer:

Characters of Kingdom Monera:

1. Body is formed of single-cell but the cells lack nuclear membrane and membrane-bound organelles such as mitochondria, chloroplasts etc.
2. They may be motile or non-motile. Flagella, if present, have a solid core and formed of flagellin protein.
3. Monerans have various forms of nutrition: some are autotrophs capable of photosynthesis, others are capable of deriving energy from inorganic chemical reaction (chemosynthetic).
4. Most species absorb organic nutrients from their environment.
5. Reproduction is asexual.
6. Some organisms may have cell wall.
7. Monerans are the important decomposers in the biosphere. Examples are Bacteria, Blue-Green algae (Cyanobacteria) and Mycoplasma.

Question 12.
What kinds of organisms are grouped under Protista?
Answer:
Characters of Kingdom Protista:

1. This kingdom includes diverse kinds of mostly unicellular and primarily aquatic eukaryotes.
2. They are eukaryotic organisms having typical eukaryotic cell organelles such as nucleus, mitochondria, ER, Golgi bodies, plastids etc.
3. Mode of nutrition may be absorptive, ingestive or photo-autotrophic.
4. Mostly bear eukaryotic flagella or cilia composed of 9 + 2 internal microtubular structure.
5. Reproduction asexual as well as sexual. Examples: Protozoan (Amoeba), Euglena, Diatoms.

Question 13.
Write the general characters of kingdom Fungi.
Answer:
Tire kingdom of multicellular decomposers is Fungi. This kingdom includes diverse kinds of eukaryotic, predominantly multicellular, heterotrophic organisms.
Characters of Kingdom Fungi:
1. Body organization mycelial or secondarily unicellular, composed of hyphae, coenocytic or septate.
2. They are non-green as chlorophyll is absent.
3. They are heterotrophic in nutrition and obtain food from dead and decaying organic matter by absorption.

4. Cell wall is chitinous cellulose
5. Asexual reproduction by spore formation.
6. Sexual reproduction also occurs.
Examples: Bread moulds, mushrooms, puff balls and bracket fungi, Penicillium, yeast and certain parasitic fungi.

Question 14.
Make a list of characteristics of kingdom Plantae.
Answer:
Kingdom Plantae. This kingdom includes multicellular producers. The characteristics are:

1. Complex multicellular plants adapted for photosynthesis.
2. The plant cells are rigid because of cellulose cell wall.
3. Mostly the cells are rigid and cannot contract and relax like animal cells do. Plants are immobile and do not exhibit the phenomenon of locomotion.
4. Plant synthesize all organic constituents from water, C02 and inorganic forms of essential elements using light energy trapped by chlorophyll and accessory pigments.
5. They have unlimited growth.

Question 15.
List the general characters of kingdom Animalia.
Answer:
Characters of Kingdom Animalia:

1. Members of the group are multicellular eukaryotes with tissue differentiation.
2. Nutrition hetero trophic, ingestive mode of intake of food.
3. Muscle cells well developed which provide mobility.
4. Nervous system well developed.
5. Ecologically animals are consumers.
6. Sexual reproduction occurs. Examples: Sponges, insects, molluscs, fishes, birds, reptiles and mammals.

Question 16.
What is binomial nomenclature? Illustrate with an example.
Answer:
In binomial nomenclature, name of every organism is composed of two components-first one is genus (generic) and second species name (specific).
Example: Scientific name of human is Homo sapiens where Homo is generic name and sapiens is specific name.

Question 17.
Give some examples of binomial nomenclature.
Answer:

• Scientific name of potato is Solanum tuberosum Linn. Where Solanum is genus, tuberosum is species and Linn is the scientist.
• Man is scientifically called as Homo sapiens Mill. Here Homo is a generic name and sapiens is specific name.
• Mill is the scientist. Sometimes specific names can be given after a country or locality e.g. Rosa indica, Rumcx nepalensis.

Question 18.
Write some advantages of binomial nomenclature.
Answer:
(a) The biological names are same all over the world.
(b) They are uniformly binomial.
(c) They are definite and accepted universally.
(d) They are descriptive.
(e) They indicate general relationship.
(f) All newly discovered plants and animals can be named and described easily.

Question 19.
Write distinguishing features of division Thallophyta.
Answer:
Characters of Division Thallophyta:
(a) Plants belonging to this group are the simplest and primitive.
(b) The plants are made up of single cell or group of cells.
(c) The plant body is thallus i.e. it is not differentiated into stem, root and leaves. id) The reproductive organs are unicellular and thus unjacketed.
(e) The zygote formed after fertilization, gives rise to either plant body directly or produces spores.
(f) Vascular tissue absent.

Question 20.
Write three characters of Algae. Give examples.
Answer:
Characters of Algae
(a) Green in colour due to chlorophyll.
(b) They are photoautotrophs.
(c) Reserve food material is starch.
Example: Chlamydomonas, Volvox, Ulothrix, Spirogyra.

Question 21.
Sketch Aspergillus, Penicillium and Agaricus.
Answer:

Question 22.
What are lichens?
Answer:
Lichens: They are organisms formed of intimate combination of an alga and fungus found in all types of habitat. It is an example of mutualism. Mycobiont is the fungal component and phycobiont an algal partner.
Example: Graphis, Parmelia and Usnea.

Question 23.
Write important characters of division Bryophyta.
Answer:
Characters of Division Bryophyta
(a) The plant body is not differentiated into root, stem and leaves (thalloid).
(b) Absorbing and anchoring organs are rhizoids.
(c) Vascular tissue and mechanical tissue absent.
(d) Vegetative reproduction is very common.
(e) Sexual reproduction is by gamete formation.
(f) Sex organs are multicellular and jacketed.
(g) Formation of sporogonium takes place.
Examples: Riccia, Porella, Punaria (Moss), Marchantia (Liverwort) and Anthoceros.

Question 24.
List four important features of Pteridophytes.
Answer:
Important features of Pteridophytes:

1. The dominant plant body in ferns is sporophyte. It is differentiated into root, stem and leaves.
2. The leaves are large (megaphyllous), variously-shaped and look like the branches. They are called as fronds.
3. The stem may be an underground rhizome or a trunk as in tree ferns while the roots are adventitious.
4. Ferns bear special spore-bearing leaves called the sporophylls. The spores are produced in sporangia.
5. Spores in ferns, germinate each forming an independent, small gametophyte, the prothallus. The latter bear the sex organs, antheridia (male) and archegonia (female).

Question 25.
Make a few diagrams of common pteridophytes.
Answer:

Question 26.
What are the two main divisions of angiosperms on the basis of number of cotyledons.
Answer:
Classification according to cotyledons
The number of cotyledons in seed of a flowering plant is either one or two. The angiosperms are divided into two groups-1. Monocotyledons and 2. Dicotyledons.
1. Monocotyledons are the plants in which the seed contains a single cotyledon; e.g. Wheat, Rice, Maize, Sugarcane, Grasses. There are about 50,000 species of them.
2. Dicotyledons are those flowering plants in which the seed contains two cotyledons.
e.g. Solarium sp, Mango, Beans, Castor, Gram, Sunflower.

Question 27.
Write two differences between gymnosperms and angiosperms.
Answer:
Differences between gymnosperms and angiosperms:

Gymnosperms	Angiosperms
1. The seeds are naked. 2. These are cone-bearing plants.	1. The seeds are present within fruits. 2. They bear flowers.

Question 28.
What characters of seed plants make them specially adapted to life on land?
Answer:
Characters of seed plants which make them specially adapted to life on land are:

1. Presence of vascular tissue.
2. The development of seed habit removed the liquid medium as an essential feature for fertilization.
3. Presence of cuticle in the leaves.

Question 29.
Write three features of kingdom Animalia.
Answer:
Features of Kingdom Animalia:

1. Eukaryotic cells lack cell wall.
2. They do not perform photosynthesis instead take readymade food, thus heterotrophs.
3. They have power of locomotion.

Question 30.
Write unique features of Coelenterates (cnidarians).
Answer:
Unique Features of Coelenterates (cnidarians)

1. Tissue level of organisation of the body.
2. Special stinging cells, the cnidoblasts, for defence and offence.
3. Incomplete digestive tract bounded by gastrodermis of body wall.
4. Simple gonads without gonoducts.
5. Show polymorphism.

Examples: Hydra, Jellyfish and Sea Anemone.

Question 31.
Write characters of flatworms. Give example.
Answer:

Characters of Flatworms:

1. Dorsoventrally flattened triploblastic, bilaterally symmetrical animals.
2. They are acoelomate.
3. Mostly parasite, a few are free living.
4. Incomplete branched or unbranched alimentary canal.
5. Bisexual or hermaphrodite. Life history is complicated. Examples: Planaria, Fasciola and Taenia.

Question 32.
Write features of roundworms.
Answer:

Features of Roundworms:

1. Unsegmented, bilaterally symmetrical cylindrical worms also called as roundworms.
2. They are triploblastic and pseudo- coelomatic.
3. Mostly free living.
4. Complete alimentary canal present.
5. Sexes are separate and show sexual dimorphism. Fertilized egg has a thick wall and survive adverse conditions. Examples: Ascaris (Roundworm), Ancylostoma (Hookworm), Dracunculus (Guinea worm), Rhabditis.

Question 33.
List unique features of phylum Annelida. Give examples.
Answer:
Unique Features of Phylum Annelida:
1. Metameric segmentation i.e. body divided externally by grooves into metameres or segments and internally bv septa into compartments.
2. Nephridia for excretion and osmoregulation.
3. Closed circulatory system with respiratory pigment dissolved in the plasma. Examples : Nereis, Pheretima (Earthworm), Ilirudinaria (Leech), Aphrodite (Sea-mouse).

Question 34.
List three important distinguishing characters of phylum Arthropoda.
Answer:
Distinguishing Characters of Phylum Arthropoda
1. Body covered with chitinous exoskeleton.
2. Body bears jointed appendages.
3. One or two pairs of jointed antennae present.
4. There is an open circulatory system, and so the blood does not flow in well defined blood vessels.

Question 35.
Write unique features of phylum Mollusca. Give three examples.
Answer:
Unique Features of Phylum Mollusca:
1. Three body regions head, visceral mass and foot.
2. A glandular fold, the mantle, over the body.
3. Mantle cavity with anal, excretory and genital apertures in it.
4. Calcareous shell around the body in most cases.

5. A rasping organ, the radula in the buccal cavity.
Examples: Pila, Sepia, Octopus.

Question 36.
What are Echinoderms?
Answer:
1. Phylum Echinodennata includes starfish, sea cucumbers, sea urchins, sea lilies etc.
2. The animals show pentaradial symmetry.
3. There is an exoskeleton of calcareous plates and spines.
4. Locomotion is by tube feet.
5. There occurs a peculiar water vascular system. Echinoderms are confined to sea.

Question 37.
Write five examples of echinoderms.
Answer:
Examples of echinoderms

1. Asterias (Star fish)
2. Sea urchin
3. Antedon (Sea lily)
4. Sea Cucumber
5. Sea cake

Question 38.
List three characters of phylum Hemichordata. Give one example.
Answer:

Characters of Phylum Hemichordata

1. Body divided into proboscis, collar and trunk.
2. Respiration through gills.
3. Bilateral symmetry.
4. Example: Balanoglossus (Tongue worm).

Question 39.
Give the general characteristics of the vertebrates.
Answer:
General Characters of Vertebrates:

1. The body is divided into three regions – a head with an internal cranium, trunk and postanal tail.
2. The notochord is replaced by vertebral column during life history.
3. Body contains cartilaginous or bony endoskeleton.
4. The post-anal part called tail is usually present.
5. There is a complex brain with special sense organs.
6. There is well developed ventral heart with two, three or four chambers.
7. Two pairs of lateral appendages, fins or limbs present.
8. The excretory organs are kidneys.
9. Respiration occurs through gills or lungs.
10. The sexes are separate.

Question 40.
Differentiate exoskeleton and endoskeleton.
Answer:
Differences between exoskeleton and endoskeleton:

Exoskeleton	Endoskeleton
1. It is present outside the body. 2. Examples: chitinuous cuticle of insects, calcareous shell of mollusc, hard plates of echinoderm, scales, feathers, hair, nails, horns of vertebrates.	1. It is present inside the body. 2. Bones and cartilages constitute the endoskeleton.

Question 41.
Write characters of class Pisces.
Answer:
Characters of Class Pisces:

1. All fish varieties belong to this class which are exclusivusingely water living animals.
2. Their skin is covered with scales/plates.
3. They obtain oxygen dissolved in water by gills.
4. The body is streamlined and a muscular tail is used for movement.
5. They are cold-blooded and their hearts have only two chambers.
6. Some fish varieties have their skeletons made entirely of cartilage, such as Sharks and some with a skeleton made of both bone and cartilage, such as Tuna or Rohu.

Question 42.
List distinguishing characters of cartilaginous fishes.
Answer:
Chondrichthyes (Cartilaginous fishes):
1. Skeleton cartilaginous
2. Mouth and nares ventral
3. Gill slits uncovered
4. Tail fin asymmetrical
5. No swim bladder
6. Intestine with scroll valve
7. Males with claspers

Examples: Scoliodon, Narcine, Torpedo, Trygon, Angler fish, Lionfish

Question 43.
List distinguishing features of bony fishes.
Answer:
Osteichthyes (Bony fishes):
1. Skeleton bony
2. Mouth anterior
3. Gill slits covered by opercula
4. Tail symmetrical
5. Swim bladder present
6. Intestine without scroll valve
7. Copulatory organs claspurs absent.

Examples: Labeo, Rita, Exocoetus, Hippocampus, Solea, Muraena, Lophius, Anabas, Protopterus.

Question 44.
Give a few features of class Amphibia.
Answer:
Features of Class Amphibia:
Amphibia (amphibians): First land vertebrates, evolved from lobe-finned bony fishes, skin naked and moist for respiration, have four limbs, digits without claws, sac-like lungs, 3-chambered heart, eggs laid in water, tailed, gill-breathing larva undergoes metamorphosis, embryonic membranes not formed.

Examples: Ichthyophis, Ram (Frog), Bufo (Toad), Salamander.

Question 45.
Write distinguishing features of class Reptilia.
Answer:
Distinguishing characters of Class Reptilia
1. Dry homy scale-covered skin present.
2. Body divisible into head, neck, trunk and tail,
3. Heart divisible into incomplete four-chambered heart.

Question 46.
Write distinct features of class Aves.
Answer:
Features of Class Aves:

1. Body covered with feathers.
2. Forelimbs modified into wings.
3. jaws absent, beak present.
4. Lungs with air sacs.

Question 47.
Write distinguishing features of class Mammalia.
Answer:
Distinguishing features of Class Mammalia:

1. Body is covered with hair.
2. Presence of rnilk produced by mammary glands.
3. Presence of pinnae or external ear.
4. Presence of diaphragm.
5. They give birth to young ones.

Question 48.
Name at least five invertebrates belonging to different groups which are of economic importance.
Answer:

1. Pearl oyster helpful in pearl industry.
2. Silkmoth spins silk.
3. Earthworm helps the farmer as an aid in ploughing.
4. Palaemon is consumed as food.
5. Bath sponge is used as bath sponge and also for making cushions.

Question 49.
Write differences between cartilaginous fishes and bony fishes.
Answer:
Differences between cartilaginous and bony fishes:

Cartilaginous Fish	Bony Fish
1. Alwavs marine.	1. May be marine or fresh water.
2. Skin covered by small placoid scales.	2. Scales are large either cycloid or ganoid.
3. Mouth is subterminal or ventral.	3. Mouth terminal.
4. Gill slits not covered by operculum.	4. Gills covered by operculum.
5. Swim bladder absent.	5. Presence of swim bladder.
6. Endoskeleton entirely cartilaginous.	6. Endoskeleton bony.
7. Tail fin asymmetrical.	7. Tail fin symmetrical.
8. Usually viviparous.	8. Oviparous.
Examples-Sharks, Rays, Sea horse.	Examples-Labeo, Catfish, Flat fish.

Question 50.
Draw a few examples of common birds.
Answer:

Question 51.
Make a flow chart of classification of Kingdom Animalia.
Answer:

Question 52.
Write differences between chardates and non-chardates.
Answer:
Differences between chordates and non-chordates:

Chordates	Non-Chordates
1. Notochord is present in some stage of the life cycle. 2. Tail is present at some stage. 3. A living endoskeleton is present. 4. Pharyngeal gill slits are present at some stages of life. 5. Digestive tract is complete. 6. Heart is ventral.	1. The notochord is absent in non- chordates. 2. Tail is absent in most cases. 3. Endoskeleton if present, is non-living. 4. Pharyngeal gill slits are absent. 5. Digestive tract may be complete, incomplete or absent. 6. Heart is absent, if present, then on dorsal or lateral side.

Very Short Answer Type Questions:

Question 1.
What is Classification?
Answer:
The method of placing organisms into groups and such groups depending upon similarities and differences.

Question 2.
Who is the father of taxonomy?
Answer:
Carl Linnaeus.

Question 3.
Define species.
Answer:
Species. It is defined as a dynamic group of organisms, which:
1.  resemble each other in all essential respects, i.e. structure and function.
2. interbreed freely under natural conditions to produce fertile young ones of their own kind.

Question 4.
Name the two groups according to old system of classification.
Answer:
1. Plant kingdom
2. Animal kingdom.

Question 5.
Who devised binomial nomenclature?
Answer:
Carolus Linnaeus.

Question 6.
Write two sub-groups of plant kingdom.
Answer:
1. Cryptogamae
2. Phanerogamae.

Question 7.
Why are algae green in colour?
Answer:
Green colour of algae is due to the presence of chlorophyll pigment in their cells.

Question 8.
How do fungi obtain their food?
Answer:
Fungi obtain their food from dead decaying matter by absorption.

Question 9.
Name two kinds of angiospermic plants.
Answer:
1. Monocotyledonous plants
2. Dicotyledonous plants.

Question 10.
Name the respiratory organ of fishes.
Answer:
Gills.

Question 11.
How many chambers are present in the heart of fishes?
Answer:
Two chambers.

Question 12.
Give examples of bony fishes.
Answer:
Labeo (Rahu), Anabas, Exocoetus, Hippocampus (Sea horse).

Question 13.
Write examples of phylum Echinodermata.
Answer:
Starfish, Sea cucumber, Sea Lily, Sea urchin, Antedon (Feather star).

Question 14.
Write examples of phylum Urochordata.
Answer:
Herdmania, Doliolum, Pyrosoma.

Question 15.
Give one example of cartilaginous fish.
Answer:
Scoliodon.

Question 16.
Name the excretory structures of flatworms.
Answer:
Flame cells

Question 17.
Name the body cavity of Nematodes.
Answer:
Pseudocoel.

Question 18.
Give the habitat of Ascaris.
Answer:
An endoparasite of intestine of man, especially children.

Question 19.
Name any two mammals.
Answer:
1. Elephant
2. Monkey

Question 20.
What are the different forms with respect to size in which life occurs on earth?
Answer:
Microscopic bacteria a few micrometres in size, the ~30 metre long blue whale and -100 metre tall redwood trees of California.

Question 21.
Name the plant having life span of more than thousand years.
Answer:
Pine trees.

Question 22.
Which division of biology helps us in exploring the diversity of life forms?
Answer:
Taxonomy.

Question 23.
Who made the first attempt to classify animals?
Answer:
Aristotle.

Question 24.
Name any five marine animals.
Answer:
Whale, Octopus, Star fish, Shark, Sea horse.

Question 25.
Name the organisms which carry out photosynthesis.
Answer:
Green plants.

Question 26.
What do you mean by characteristics?
Answer:
Characteristic is a particular form or function of a living organism.

Question 27.
What is a prokaryotic cell?
Answer:
Prokaryotic cell. A cell without clearly demarcated nucleus and membrane-bound organelles.

Question 28.
Give examples of prokaryotes.
Answer:
Prokaryotes (monerans) includes bacteria, blue-green algae.

Question 29.
What is evolution?
Answer:
Descent with modification.

Question 30.
Who wrote the book ‘Origin of species’?
Answer:
Charles Darwin (1859).

Question 31.
What are primitive animals?
Answer:
The group of animals which have ancient body divisions and have not changed very much. They are also called lower organisms.

Question 32.
Define advanced organisms.
Answer:
The group of organisms that have acquired their particular body design relatively recently, also called ‘higher’ organisms.

Question 33.
Name five kingdoms as proposed by R.H. Whittaker.
Answer:
Monera, Protista, Fungi, Plantae, Animalia.

Question 34.
What are basis of five kingdom classification as proposed by Whittaker?
Answer:
1. Nature of cells
2. Number of cells
3. Mode of nutrition

Question 35.
Name the two divisions as proposed by Karl Woose.
Answer:
1. Archaebacteria
2. Eubacteria

Question 36.
Name the various taxonomic categories.
Answer:
Species, genus family, order, class, phylum and kingdom.

Question 37.
Name the tnree aspects of systematics.
Answer:
Identification, nomenclature and classification.

Question 38.
What is highest taxonomic category?
Answer:
Kingdom.

Question 39.
What is the nature of cells of monerans?
Answer:
Prokaryotic cell.

Question 40.
Name the kind of mode of nutrition in kingdom Monera,
Answer:
Autotrophic and Saprotrophic.

Question 41.
Give examples of kingdom Monera.
Answer:
Bacteria, Cyanobacteria and Mycoplasma.

Question 42.
Write locomotory structures of kingdom Protista.
Answer:
1. Cilia
2. Flagella

Question 43.
Write examples of Protista.
Answer:
Single-celled algae, Protozoa (Fuglena, Amoeba) and Diatoms.

Question 44.
Give examples of Fungi.
Answer:
Yeast, Mushroom, Mucor, Rhizopus.

Question 45.
What is the mode of nutrition of Fungi?
Answer:
Fungi obtain their food from dead decaying organic matter.

Question 46.
What is symbiosis?
Answer:
An inter-relationship between two different species e.g. Lichens.

Question 47.
Write few characters of kingdom Animalia.
Answer:
1. Eukaryotic
2. Multicellular
3. Heterotrophic mode of nutrition

Question 48.
What is thallus-like plant body?
Answer:
When there is no differentiation of the plant body into root, stem and leaves.

Question 49.
Give few examples of Bryophytes.
Answer:
Riccia, Mardmntia, Funaria (Moss).

Question 50.
Name the division which is called ‘amphibians of plant kingdom’.
Answer:
Bryophyta.

Question 51.
What is hypha?
Answer:
In fungi, thallus is made up of colourless filamentous structure called hypha.

Question 52.
What is the mode of nutrition in Fungi?
Answer:
Absorptive-saprophytic, Heterotrophic.

Question 53.
Name the group in which seeds are naked.
Answer:
Gymnosperms.

Question 54.
Name the group in which reproductive organs are flowers.
Answer:
Angiosperms.

Question 55.
Name the class of angiosperms in which reticulate venation is present.
Answer:
Dicots.

Question 56.
Name the class of organisms in which leaves show parallel venation.
Answer:
Monocots.

Question 57.
Name the reproductive organ of Angiosperms.
Answer:
Flower.

Question 58.
What are cryptogams?
Answer:
Cryptogams are flowerless, seedless, lower plants.

Question 59.
What are phanerogams?
Answer:
Phanerogams are seed bearing plants.

Question 60.
What are Algae?
Answer:
These are green, autotrophic thallophytes.

Question 61.
Write examples of dicot plants.
Answer:
Pea, Gram, Rose.

Question 62.
How do oviparous and viviparous animals differ from each other?
Answer:
Oviparous animals lay eggs e.g. birds, while viviparous animals give birth to young ones e.g. most of mammals.

Question 63.
What are hermaphrodite animals?
Answer:
Animals which have both male and female reproductive organs e.g. earthworm, leech, etc.

Question 64.
Name the skeletal elements of sponges.
Answer:
Spicules (needles) or spongin fibres or both.

Question 65.
What are cnidoblasts? Give their function.
Answer:
These are stinging cells present on the tentacles of coelenterates like Hydra. These inject the hypnotoxin and paralyze the prey.

Question 66.
Name the cavity present in the body of Coelenterates.
Answer:
Coelenteron.

Question 67.
Mention two characters of sponges.
Answer:
Presence of two types of pores (dermal ostia and osculum) and collar cells.

Question 68.
Which characters appeared for the first time in the flatworms?
Answer:
Triploblastic, bilateral symmetry and organ-system organisation.

Question 69.
Write two examples of phylum Annelida.
Answer:
Earthworm, Leech.

Question 70.
Write two examples of phylum Coelenterata.
Answer:
Hydra, Obelia.

Question 71.
Name five animals belonging to kingdom Arthropoda.
Answer:
Prawn, Butter fly, Housefly, Spider, Crab, Body Louse.

Question 72.
Write two examples of phylum Mollusca.
Answer:
Pila, Unio, Cuttlefish.

Question 73.
Give two examples of phylum Echinodermata.
Answer:
Star Fish, Sea lily.

Question 74.
What is primary unit of classification?
Answer:
Species.

Question 75.
What were the two most outstanding contributions of Linnaeus to the modem science of taxonomy?
Answer:
The outstanding contributions of Linnaeus were his method of grouping species in a hierarchy and his binomial method of nomenclature.

Question 76.
What is a genus?
Answer:
Group of related species.

Question 77.
Why do species included in a genus resemble in many features?
Answer:
Because they have originated from a common ancestor.

Punjab State Board PSEB 9th Class Science Important Questions Chapter 6 Tissues Important Questions and Answers.

PSEB 9th Class Science Important Questions Chapter 6 Tissues

Long Answer Type Questions:

Question 1.
Define tissue, Differentiate meristematic and permanent tissue, Describe different types of primary meristematic tissue.
Answer:
Tissue, A tissue is a group of similar or dissimilar cells coordinating to perform a specific function.

Meristematic tissue	Permanent tissue
1. Cells are thin walled, living, oval or rounded, and isodiametric.	1. Cells are thin or thick walled, living or dead, oval or rounded or elongated fibre-like.
2. Divide throughout life so help in growth.	2. Lost the division power, so do not help in growth.
3. Reserve food is absent.	3. Reserve food may be present.
4. Vacuoles are absent.	4. Vacuoles are present.

Types of primary meristematic tissues. On the basis of their position, these are of three types:

1. Apical meristem lies at shoot and root apices and helps in longitudinal growth.
2. Intercalary meristem lies between shoot and root apices and helps in longitudinal growth.
3. Lateral meristem lies on lateral sides of stem and root and helps in increase in diameter.

Question 2.
What is permanent tissue? Briefly explain the types of simple permanent tissue.
Answer:
Permanent Tissue: They are composed of mature cells which after undergoing complete growth have assumed a definite shape, size and function. They have lost the power of division. The permanent tissues are of two types i.e. simple tissue and compound tissue.
Kinds of simple tissue:
1. Parenchyma
2. Collenchyma
3. Sclerenchyma

1. Parenchymal tissue is formed of thin walled, living, oval cells having walls formed of only cellulose. It forms cortex, endodermis, pericycie, pith etc. of different parts of plants. It is loosely packed with intercellular spaces. It is modified to form epidermis covering of all the parts of plant body, chlorenchyma for photosynthesis, aerenchyma for floating in the hydrophytes.

2. Collenchyma is formed of thick walled (with pectinised cell wall) and living cells and is found in hypodermis of dicot stem. It provides flexibility to plants.

3. Sclerenchyma is formed of thick walled (with lignified cell wall) and dead cells and forms hypodermis of monocot stem, bark, shells of nuts, etc. It makes the plants hard and stiff. It provides strength to plant parts. It also forms hard covering of seeds and nuts.

Question 3.
What is complex tissue? Explain its types along with diagrams.
Answer:
Complex tissue. The tissue formed of two or more than two kinds of tissue is called complex tissue. It is of two types:
1. Xylem
2. Phloem

1. Xylem, also called wood, is compound tissue of the plants which primarily helps in conduction of water and minerals from the root system to various parts of shoot system (Ascent of sap).

Xylem elements	Function
1. Tracheids 2. Tracheae or vessels 3. Xylem parenchyma 4. Xylem sclerenchyma	1. Long-distance conduction of water and minerals upward from the root system to various parts of shoot system. 2. Storage and short distance conduction of water and minerals. 3. Mechanical support so helps in resisting strong winds.

(a) Element of xylem

(b) Kinds of xylem
1. Primary xylem. It is derived from procambium during the formation of primary plant body, developing from embryo.
2. Secondary xylem. It is formed from cambium, during secondary growth of plant development when increase in thickness takes place.

2. Phloem, also called bast, is a compound tissue which helps in downward conduction of food.

Phloem elements	Function
1. Sieve tube cells 2. Companion cells 3. Phloem parenchyma 4. Phloem sclerenchyma	Long-distance conduction of food from the leaves to other parts of plant body. Control the functioning of dead sieve tube cells. Storage and short distance conduction of food. Mechanical support.

Question 4.
List various forms of connective tissue and write functions of each.
Answer:
Kinds of connective tissue:

1. Proper connective tissue: It joins the body parts, such as blood vessels and nerves.
2. Bone: It is the hardest tissue: It forms skeleton and provides shape to body. It protects the body organs.
3. Cartilage: It forms parts of endoskeleton. It forms tip of nose, pinna, ends of long bones.
4. Blood: It is fluid tissue. It transports materials and gases in the body.
5. Tendon: It connects muscles with bone.
6. Ligament: It connects bone with bone.

Question 5.
Give an account on types of epithelia.
Answer:
Simple epithelium is unilaminar in which cells are arranged in only one layer. It is found in those parts of body where wear and tear are less. Types of simple epithelial tissues are:

Type of Epithelium	Structure	Positive	Function
1. Squamous epithelium	Cells are flat, discoidal  and polygonal and fit like the tiles in a floor.	Alveoli of lung. Bowman’s capsule of nephron. Blood capillaries.	Exchange of gases. Ultrafiltration. Exchange between body cells and blood.
2. Cuboidal epithelium	Cells are polygonal and cuboidal with centric and rounded nuclei.	Proximal part of body of nephron (with micro-villi). In gonads.	Selective reabsorption of useful materials. Divide by meiosis and form gametes.
3. Columnar epithelium	Cells are polygonal and pillar-like with oval-shaped nuclei.	Fallopian tube (cells) with cilia. Mucosa of small intestine (with microvilli).	Move ovum/zygote. Increased absorption of nutrients.
4. Ciliated epithelium	Free ends of cells bear cilia.	Uriniferous tubules, trachea and fallopian tubes.	Flow of materials
5. Glandular epithelium	These are cuboidal gland cells.	Lining of alimentary canal and digestive gland.	Secretion of useful substances.

Question 6.
Give an account on the types of animal tissue.
Answer:

• Epithelial tissue is covering and protective tissue and is formed of one or more layers of compactly arranged cells with no intercellular spaces and resting on basement membrane.
• Muscular tissue is formed of highly elongated and useful secretion contractile cells called muscle fibres. It helps in movements of body parts and locomotion.
• Muscular tissue is of three types:
  • Striated or skeletal muscular tissue.
  • Visceral or smooth or unstriated muscular tissue.
  • Cardiac muscular tissue.
• Connective tissue mainly acts as binding tissue and has large amount of matrix.
• Connective tissue is of three types: Connective tissue proper, Skeletal connective tissue and Vascular connective tissue.
• Connective tissue proper: Areolar connective tissue has soft matrix. Yellow fibrous connective tissue (with many elastic fibres and forms ligaments); Adipose connective tissue (with large number of fat-storing adipocytes e.g. below the skin of mammals, fat- bodies of frog, etc.)
• Skeletal connective tissue has dense and mineralised matrix and forms endoskeleton of vertebrates. It includes cartilages and bones.
• Vascular connective tissue has fluidy and fibre-free matrix. It is of two types: Blood and Lymph.
• Blood is red vascular connective tissue and flows inside the blood vessels. It is formed of plasma and blood corpuscles which are of three types: Erythrocytes or RBCs mainly with haemoglobin.
• Leucocytes or WBCs (rounded or amoeboid and nucleated corpuscles and Blood platelets (cytoplasmic fragments and help in blood clotting at the injury’).
• Lymph is white vascular connective tissue and flows inside the lymph-vessels. It is formed of plasma and leucocytes so is called filtered blood. It acts as middle man between body cells and blood.
• Nervous tissue has the properties of excitability and conductivity of nerve impulses.
• Neurons are structural and functional units of nervous tissue. Neurons receive and conduct impulses.
• Each neuron is formed of a nucleated cyton and one or more nerve processes which are of 2 types: Axon or efferent and dendron or afferent.
• When axon (acts as neuraxis) is surrounded by one or more sheath, then it is called nerve fibre.
  Nerve fibres are of two types: Medullated nerve fibres and Non-medullated nerve fibres.

Short Answer Type Questions:

Question 1.
What is a tissue? What are its kinds?
Answer:
Tissue: A tissue is a group of cells having a similar origin along with intercellular material and performing a similar function. The different cells of a tissue are usually joined together. The microscopic study of tissues is called histology.

Depending upon the constitution, their structure and arrangement, tissues are of two types-simple and complex (= compound).
A simple tissue is made up of only one type of cells while a complex tissue consists of two or more types of cells.

Question 2.
What are the kinds of meristem depending upon location?
Answer:
Depending upon the position (location) in the plant body, the meristems may be apical, intercalary and lateral.

1. Apical meristems are bom at the tips of the stems, roots and their branches.
2. Intercalary meristems are the left-out portions of the apical meristems that get separated from the latter by the differentiation of permanent tissues in-between meristems at the base of leaves or inter- nodes.
3. Lateral meristems are located along the lateral sides of stems and roots.

Question 3.
How will you prove that growth occurs in certain specific regions of plant?
Answer:
Apical meristem causes growth in length.
Materials: Two jars, two onion bulbs, water, pair, of scissors and measuring scale.

Procedure:

1. Take two glass jars and fill them with water.
2. Now, take two onion bulbs and place one on each jar as shown in the Fig.
3. Observe the growth of roots in both the bulbs for a few days.
4. Measure the length of roots on day 1,2 and 3.
5. On day 4, cut the root tips of the onion bulb in Jar-II by about 1 cm.

After this, observe the growth of roots in both the jars and measure their lengths each day for five more days and record the observations in tables like the table below:

Length	Day 1	Day 2	Day 3	Day 4	Day 5
Jar-I
Jar-II

Observation:
1. Roots of Jar-1 continue to grow on 5th and 6th day. They stop in case of Jar-II. Conclusion. It is due to the fact that apical meristem remains intact in case of Jar-I which is responsible for growth Thus growth occurs in specific regions.

Question 4.
What are different kinds of animal tissue? Give one example and one function of each type.
Answer:
Types of animal tissues:

Name of tissue	Example	Function
Epithelial Tissue	Internal and external surfaces of body and its organs	Protection
Connective Tissue	Bone, Cartilage, Areolar tissue, Blood	Connects two similar or different types of tissues together.
Muscular Tissue	Body wall, Limbs, Tongue, Face.	Movement and protection.
Nervous Tissue	Brain and Spinal cord.	Conduction of messages and coordination of various parts of body.

Question 5.
Describe the salient features of meristematic tissue.
Answer:
Characteristic features of meristematic tissue are as follows:

1. They consist of immature cells which are in a state of division and growth.
2. They are compactly arranged so that there are no intercellular spaces in between them.
3. The cells have thin walls.
4. Each cell consists of a prominent nucleus and dense cytoplasm.
5. Vacuole in the cells is usually absent, if present it is quite small.

Question 6.
Write characteristics of permanent tissues.
Answer:
Permanent tissues are those tissues whose cells have lost the power of division and become structurally and functionally specialised.
Characteristics of permanent tissue are as follows:

1. The cells have lost the power of division.
2. They have undergone differentiation into specific types, for a particular function.
3. Permanent tissues are of two types:
   1. Simple permanent tissues, where the tissue is composed of only one type of cells.
   2. Complex permanent tissues, where the tissue is composed of more than one type of cells.

Question 7.
Differentiate meristematic cells and permanent cells.
Answer:
Differences between meristematic cells and permanent cells:

Meristematic cells	Permanent cells
1. These cells do not have large vacuoles. 2. They are thin-walled and isodiametric. 3. These cells can divide and produce new cells.	1. These cells often have large central vacuoles. 2. They may be thin or thick-walled. They have permanent shape. 3. These cells have lost the power of growth and cell division.

Question 8.
What are the characteristics of parenchyma? Give two examples of specialized parenchyma cells.
Answer:
Parenchyma. It is the most common type of simple permanent tissue found in almost all the parts of the plant.
Characteristics of parenchyma:
1. It is the main representative of the ground tissue system. It forms a continuous soft tissue, as in the cortex and pith of stems, cortex of roots, ground tissue, petiole, mesophyll of leaves.
2. It is thin-walled.
3. They retain the ability to divide at maturity.
4. The cells of parenchyma vary in their shape, but a typical ground tissue parenchyma cell is equal in length and width.
5. Parenchyma of stems and roots stores nutrients and water.

Examples of specialized parenchyma:

• Chlorenchyma. In some cases the parenchyma cells contain chloroplasts and are called as chlorenchyma. These cells are meant for photosynthesis.
• Aerenchyma. In aquatic plants parenchyma cells occur around air cavities, they are called as aerenchyma e.g. in Hydrilla stem. Aerenchyma provides buoyancy to the plants to help them float.

Question 9.
Mention any two functions of parenchyma.
Answer:
Functions of parenchyma:

• It provides rigidity and also stores food in the form of starch, proteins, oil and fats.
• In hydrophytes they have large air spaces to keep up buoyancy of plants.

Question 10.
Explain the structure and functions of collenchyma.
Answer:
Structure of collenchyma. It is a special type of parenchyma having localised thickenings on the cell walls and is found only in the primary body. The cells are longer than ordinary’ parenchyma. It is a soft tissue having a pliable primary wall. Tire thickening of the corners of the cells is due to the addition of cellulose and pectin.
Functions:

1. Provide flexibility as allows easy bending in different parts.
2. It provides rigidity and strength,
3. Chloroplast containing collenchyma takes part in photosynthesis.

Question 11.
What is sclerenchyma? What are its two main kinds?
Answer:

Sclerenchyma: The cells of this tissue have very thick cell walls. Most of these cells may be dead. They are long and narrow as walls are thickened due to lignin. They provide mechanical support to the plants and parts. Sclerenchyma cells are generally of two types i.e. Fibres and sclereids.

Question 12.
State the location and one function of each of the following tissues: Parenchyma, Sclerenchyma and Collenchyma.
Answer:

Name of tissue	Location	Function
1. Parenchyma	Soft parts	Store food
2. Sclerenchyma	Stems and veins	Strength to the plant
3. Collenchyma	Leaf stalk and below epidermis of leaf	Support and Photosynthesis

Question 13.
Differentiate parenchyma and collenchyma.
Answer:
Differences between parenchyma and collenchyma:

Parenchyma	Collenchyma
1. The cell walls are uniformly thickened.	1. The ceil walls get extra thickened at places.
2. Parenchyma does not have any permanent mechanical function except when its cells are turgid.	2. Tt is a living mechanical tissue.
3. Parenchyma is formed both in the outer and inner parts of plant organs.	3. It is mostly restricted to outer parts of plant organs.

Question 14.
Write functions of xylem and phloem.
Answer:
Functions of xylem:

• It is mainly responsible for conduction of water and minerals.
• Provides mechanical strength.

Functions of phloem:

• Phloem transports food from leaves to other parts.
• Phloem parenchyma helps in storage of food.
• Materials can move in both directions.

Question 15.
Differentiate skeletal and smooth muscles.
Answer:
Differences between skeletal (striped) and smooth muscles (unstriped)

Skeletal muscles (striped)	Smooth muscles (unstriped)
1. Muscle fibres are cylindrical and unbranched. 2. Multiruicleate and nuclei lie in the peripheral region. 3. Striated due to presence of dark and light bands.	1. Fibres are spindle-shaped and unbranched. 2. Uninucleate and nucleus lies in the middle. 3. Non-stria ted.

Question 16.
List the functions of bone.
Answer:
Functions of bone:

1. It forms framework of the body.
2. It provides definite shape to the body.
3. It protects the internal organs of body such as brain, spinal cord, heart and lungs.
4. It provides solid surface for attachment of muscles so that they may act as system of levers in motion and locomotion.
5. Skeleton stores certain mineral reserves.
6. R.B.Cs. are formed in the bone marrow.

Question 17.
Write a note on blood.
Answer:
Blood. It consists of plasma, red blood corpuscles, white blood corpuscles and platelets, circulates in blood vessels. Red corpuscles are circular, biconcave and enucleated in mammals, carry O₂ and CO₂. White corpuscles are nucleated, have granular or non-granular cytoplasm, and defend the body. Platelets help in blood clotting. Plasma transports materials and contains proteins that maintain osmotic pressure, help in blood clotting and act as antibodies.

Question 18.
Explain the structure of xylem elements.
Answer:
Structural elements of xylem
(a) Tracheids are elongated, dead cells with large cavities and possess highly lignified thick-walls. Depending upon the kind of thickenings, tracheids may be annular, spiral, reticulate, scleriform and pitted.
(b) Vessels are broader as compared to the tracheids. These are composed of many cells joined end to end with their walls perforated to give it a tube-like appearance. They also show thickenings like the tracheids.
(c) Xylem Parenchyma (= Wood Parenchyma). It is parenchyma present in xylem. The cells are, however smaller and thick-walled. Xylem parenchyma stores food and helps in lateral conduction of sap or water.
(d) Xylem Fibres (= Wood Fibres). They represent sclerenchyma fibres present in xylem. The fibres are mechanical in function.

Question 19.
Give a brief account of components of phloem.
Answer:
Phloem. It is a complex permanent tissue which conducts organic materials inside the plant. Phloem consists of four types of cells-sieve tubes, companion cells, phloem parenchyma and phloem fibres. Except for phloem fibres, phloem cells are living cells.
(a) Companion Cells. They are narrow, elongated, nucleated cells which are connected to sieve tube cells.
(b) Phloem Parenchyma. It is parenchyma associated with phloem. The cells store food and take part in slow lateral conduction of the same.
(c) Phloem Fibres. Sclerenchyma fibres found in phloem are known as phloem or bast fibres. They provide mechanical strength.
(d) Sieve Tubes. They are tubular cells with perforated walls. They are tubular channels which are formed by end to end arrangement of a number of cells called sieve tube cells or sieve elements. They bear a number of small sieve pores. Due to the presence of sieve pores, the end walls are also called sieve plates.

Question 20.
Make a list of functions of blood.
Answer:
Functions of Blood:

1. It delivers the nutrients to the tissue and carries the waste products away from tissue.
2. It transports carbon dioxide from various organs to lungs.
3. It transports hormones.
4. Its components act as carrier of antibodies and antitoxic substances.
5. It conducts heat of skin for dissipation.
6. It acts as carrier of nitrogenous waste material like urea etc. to kidneys for elimination.
7. It maintains water balance in the body.
8. It maintains constant temperature in body after distributing heat within the body.

Functions of RBC:

• They transport O₂ to tissues from respiratory organs as oxyhaemoglobin.
• Erythrocytes also participate in transport of C0₂ Mainly C0₂ is carried as bicarbonate.
• Function of WBC. Act as soldiers.

Question 21.
What is muscular tissue?
Answer:
Muscular Tissue:
The muscular tissue is a contractile tissue consisting of very large cells. Excitability and contractility are properties of protoplasm called sarcoplasm which is very well developed in these tissues. These cells bring about locomotion and movement of internal organs. Based on structural and functional differences, three types of muscles are recognised. They are unstriated, striated and cardiac muscles.

Question 22.
What are main functions of muscular tissue? Name the three kinds of muscular tissue.
Answer:
Functions:

• The muscular tissues help in protection of body.
• The muscles bring about various kinds of movements.

Types of muscular tissue:
The muscular tissue is of three kinds:

1. Unstriated or visceral muscle fibres.
2. Striated or skeletal muscle fibres.
3. Cardiac muscle fibres.

Question 23.
1. Write the similarities between cardiac muscles and striped muscles.
2. Outline two similarities between smooth and cardiac muscles.
Answer:
1. Similarities of cardiac muscles with striped muscles:

• Both are striated and bear dark and light bands.
• Both are cylindrical in shape.
• Blood supply is abundant.

2. Similarities between smooth and cardiac muscles:

• Nucleus is present centrally in both muscles.
• Both are involuntary muscles.

Question 24.
Differentiate tendon and ligament.
Answer:
Differences between tendon and ligament:

Tendon	Ligament
1. It is an inelastic band. 2. Tendon connects a muscle with a bone. 3. Yellow fibres are absent. 4. Bundle of white fibres occur in parallel series.	1. It is an elastic band. 2. Ligament connects one bone with another bone. 3. Yellow fibres are present. 4. Bundles of white fibres run in different directions.

Question 25.
Bring out two points of differences between Bone and Cartilage.
Answer:
Differences between bone and cartilage:

Cartilage	Bone
1. It is a soft tissue. Perichondrium, covers the cartilage externally.	1. It is hard. It is covered by periosteum.
2. Matrix is not arranged in lamellae.	2. Matrix is arranged in concentric layers called lamellae.
3. Marrow cavity and bone marrow absent.	3. In the centre of bone, marrow cavity is present. Marrow cavity is filled with bone marrow.

Question 26.
What is nervous tissue?
Answer:
Nervous Tissue. It forms the nervous system. It is made up of neurons, nerve cells and neuroglia cells. Nerve cell (neuron) consists of a cell body or cyton containing nucleus, one long process called axon and many short branched processes called dendrites. Nervous system is concerned with responsiveness of animals.

Question 27.
Describe neuron.
Answer:
Nerve Cells (Neurons): May be unipolar, bipolar or multipolar, with one axon and one or more dendrons. Dendrites carry nerve impulses towards the cell body and axon away from it. Cell body has Nissl’s granules in the cytoplasm, Axons form synapses with the dendrites and cell body or axon of some other neuron.

Question 28.
What is nerve fibre? Name the two main types.
Answer:
Nerve Fibres. These are extended axons or dendrites. There are two types:

• Medulliated Nerve Fibres. These have thick myelin sheath, occur in white matter of brain and spinal cord and in cranial and spinal nerves.
• Non-medullated Nerve Fibres. These have very thin myelin sheath, occur in sy mpathetic nerves.

Question 29.
What is white fibrous connective tissue? Explain tendon and ligament.
Answer:
White Fibrous Connective Tissue. It is a silvery white connective tissue which contains abundant white fibres. Yellow fibres are rare. The tissue occurs at the joints of sk ull bones and covering sheaths of hone, cartilage, muscles, etc.
1. Tendoin, It is a connective tissue which binds skeletal muscles to the bones. The tissue occurs; in small bands. It contains abundant parallel bundles of white fibres with flattened tendon cells of fibroblasts found in rows in between them.
2. Ligament. It is an. elastic connective tissue which connects one bone with another. In temaliy it contains bundles of white fibres running in different directions and scattered yellow fibres. Fibroblasits occur in between the bundles of white fibres.

Question 30.
Differentiate R.B.C. and W.B.C.
Answer:
Differences between RBC (erythrocytes) and WBC (leucocytes)

Red blood cells (Erythrocytes)	White blood cells (Leucocytes)
1. Circular, biconvex in shape. 2. Coloured red due to pigment haemoglobin. 3. Occur in very large numbers (approx. 4 to 6 million per cubic mm). 4. Concerned with oxygen transport.	1. Irregular or amoeboid in shape. 2. Colourless due to absence of pig­ments. 3. Less numerous than R.B.C.s (approx. 5,000-7,000 per cubic mm). 4. Protect body against infections.

Question 31.
What is connective tissue? List the different kinds of connective tissue.
Answer:
Connective Tissue:
As the name suggests, it connects or binds the similar or different kinds of tissues. Cells are scattered and intercellular space is filled with matrix. Cells of connective tissue characteristically secrete ground substance called matrix. In the matrix are present cells and fibres.
The nature and function of each connective tissue is determined by the nature of the matrix. Connective tissue is of following types:
(a) Proper connective tissue (jelly-like matrix).
(b) Skeletal (matrix-tough impregnated with salts)-Bone and cartilage.
(c) Vascular tissue (fluid-matrix)-Blood and lymph.

Question 32.
Differentiate cardiac muscles and striated muscles.
Answer:
Differences between cardiac muscle and striated muscles:

Cardiac muscles	Striated muscles
1. These are also called involuntary muscles. 2. These are exclusively present in the heart. 3. Sarcolemma is absent in cardiac muscle. 4. Light and dark bands are absent.	1. These are also called voluntary muscles. 2. These are mostly attached to bones by tendons. 3. Sarcolemma is present in striated muscle. 4. Alternate light and dark bands are present in striated muscles.

Question 33.
Describe the structure of a neuron.
Answer:
A neuron is longest cell of body (about 1 metre) and is structural and functional unit of nervous system. It is formed of two parts:
1. Cyton or cell body.
2. Nerve processes.
1. Cyton or cell body: It is the nucleated part of neuron whose cytoplasm is called neuroplasm and has fine threads called neurofibrils (for conduction of nerve impulses), RER-rich Nissl’s granules (for protein synthesis) and many mitochondria but no centriole.
2. Nerve processes. There are protoplasmic processes arising from the cyton and are of two types: Axon and dendron.

Question 34.
Differentiate axon and dendron.
Answer:
Differences between axon and dendron

Characters	Axon	Dendron
1. Number	Always single.	Maybe one or more.
2. Size	Long sized and may or may not be branched.	Small-sized and always branched.
3. Function	These conduct nerve impulses away from cyton so are efferent in nature.	Conduct the nerve impulses towards the cyton so are afferent in nature.

Question 35.
Draw diagrams showing:
(a) Squamous epithelium
(b) Cuboidal epithelium
(c) Columnar epithelium
Answer:

Question 36.
Name three types of connective tissues on the basis of nature of matrix.
Answer:

1. Connective tissue proper with soft matrix.
2. Skeletal connective tissue with dense and mineralised matrix.
3. Vascular connective tissue with fluidity and fibre-free matrix.

Question 37.
What is the main difference in the matrix of cartilage and bone?
Answer:
Matrix of cartilage is formed of proteins and sugars but generally lacks calcium salts. Matrix of bone is formed of protein and is deposited with salts of phosphates of calcium and magnesium.

Question 38.
List two typical features of plant tissues with regard to functions.
Answer:
Features of plant tissue:

• Supportive which provide them with structural strength.
• Presence of meristematic tissues localised in certain selected region.

Question 39.
Why are most of tissues of animals are living as compared to plants?
Answer:
The animals move around in search of food, mates and shelter and consume more energy as compared to plants. Thus they are living.

Question 40.
Differentiate collenchyma and sclerenchyma.
Answer:
Differences between collenchyma and sclerenchyma:

Collenchyma	Sclerenchyma
1. Collenchyma consists of living cells. 2. The cells have wide lumen. 3. The wall is thickened unevenly with cellulose being the main constituent of thickening. 4. Pits are simple, straight and unbranched. 5. It provides both mechanical strength as well as elasticity.	1. It is generally formed of dead cells. 2. Lumen is narrow. 3. The wall is uniformly thickened. The thickening can be cellulose, lignin or both. 4. Pits are simple, oblique and may be branched. 5. Sclerenchyma provides stiffness or mechanical strength.

Question 41.
Give broad outline classification of connective tissue.
Answer:

Question 42.
Differentiate muscle fibres and nerve cells.
Answer:
Differences between muscle fibre and nerve cell

Muscle fibre	Nerve cell
1. The muscle cells are elongated in the Torm of fibres and are contractile.	1. Irregular in shape with one long process.
2. Cytoplasm is called sarcoplasm and fibre may be surrounded by sarcolemma.	2, Cytoplasm is called neuroplasm and neurilemma absent.
3. May have single nucleus or many nuclei.	3. Uninucleated.
4. Dark and light bands may be present.	4. Absent.
5. No protoplasmic processes are given out.	5. Protoplasmic processes called dendrites and axon are given out from the cell body.
6. They are concerned with movement and protection.	6. They form part of tire nervous system and bring about co-ordination.

Question 43.
Write a note on areolar tissue. Sketch the type of cells present in it.
Answer:
Areolar tissue. It is a typical connective tissue. It consists of a non-living ground substance called matrix. In the matrix are present cells. The cells are of three types:

(a) Oval shaped mast cells, they secrete matrix and contain histamine,
(b) Fibroblasts are irregularly shaped flat cells with long protoplasmic processes which form fibres and
(c) Macrophages. They are amoeboid shaped and engulf the foreign particles by phagocytosis.

Question 44.
Compare xylem and phloem.
Answer:
Differences between xylem and phloem

Xylem	Phloem
1. The conducting cells are vessels. 2. Xylem conducts water and minerals. 3. Xylem lies deeper in plant organs. 4. Xylem also provides mechanical strength. 5. There is one way conduction of materials.	1. The conducting cells are phloem sieve tubes. 2. Phloem translocates organic food. 3. Phloem is situated towards outer side. 4. Phloem has no mechanical function. 5. Materials can move in both directions.

Very Short Answer Type Questions:

Question 1.
Define tissue. Name two types of plant tissues.
Answer:
Tissue is a group of similar or dissimilar cells coordinating to perform a specific function so as to give highest possible efficiency.
Tvto types of plant tissues are: Meristematic and Permanent tissue.

Question 2.
Name two types of plant tissue.
Answer:

• Meristematic tissue
• Permanent tissue.

Question 3.
Give the term for a group of cells capable of division throughout life.
Answer:
Meristem.

Question 4.
Name three types of meristematic tissues.
Answer:

1. Apical meristem
2. Intercalary meristem
3. Lateral meristem.

Question 5.
What is apical meristem?
Answer:
Meristem present at the tips of root and stem and their branches.

Question 6.
How is permanent tissue formed from meristematic tissue?
Answer:
Cells take up specific role and lose ability to divide, it is termed differentiation.

Question 7.
What are two kinds of permanent tissue?
Answer:
1. Simple permanent tissue
2. Complex tissue.

Question 8.
What is simple tissue?
Answer:
The tissue formed of only one kind of cells is called simple tissue.

Question 9.
Name three kinds of simple tissue.
Answer:

1. Parenchyma
2. Collenchyma
3. Sclerenchyma.

Question 10.
What is the function of parenchyma?
Answer:
Storage of food, photosynthesis, and short distance conduction.

Question 11.
Give the function of collenchyma.
Answer:
Mechanical support and may become photosynthetic.

Question 12.
What is function of sclerenchyma?
Answer:
Sclerenchyma is chief mechanical supporting tissue.

Question 13.
What is complex tissue?
Answer:
Tissue formed of two or more than two kinds of tissue is called complex tissue.

Question 14.
What are two kinds of complex tissue?
Answer:
1. Xylem 2. Phloem.

Question 15.
Name four elements of xylem.
Answer:

1. Xylem parenchyma
2. Tracheid
3. Vessels
4. Xylem fibres.

Question 16.
List four elements of phloem.
Answer:

1. Sieve tubes
2. Phloem parenchyma
3. Companion cells
4. fibres.

Question 17.
What are four kinds of animal tissue?
Answer:

1. Epithelial tissue
2. Muscular tissue
3. Connective tissue
4. Nervous tissue.

Question 18.
Differentiate two types of epithelial tissue.
Answer:
Simple epithelial tissue is unilaminar, while compound epithelial tissue is multilaminar.

Question 19.
Name three kinds of muscle fibres.
Answer:

1. Smooth muscle fibres
2. Striped muscle fibres
3. Cardiac muscle fibres.

Question 20.
Which type of muscle fibres show rhythmic contraction?
Answer:
Cardiac muscle fibres.

Question 21.
Write two functions of connective tissue.
Answer:
1. Connect different organs.
2. Protection of internal organs.

Question 22.
Write names of different types of connective tissue.
Answer:

1. Bone
2. Cartilage
3. Blood
4. Tendon
5. Ligament.

Question 23.
What are the smallest unit of living organisms?
Answer:
Cells.

Question 24.
Give the function of stratified epithelium.
Answer:
Protection of the body organs from mechanical injuries, entry of germs and evaporation of water.

Question 25.
List two functional peculiarities of muscle fibres.
Answer:
1. Excitability
2. Conductivity

Question 26.
Why are the smooth muscle fibres called visceral muscle fibres?
Answer:
These are present in layers in the wall of visceral organs of body.

Question 27.
Why are the striated muscle fibres called voluntary muscle fibres?
Answer:
Because these are under the will of an animal.

Question 28.
Which structures are responsible for flexibility of plants?
Answer:
Presence of collenchyma.

Question 29.
Meristematic tissue is associated with which kind of organisms?
Answer:
Plants.

Question 30.
Which tissue is responsible for conduction of food in plants?
Answer:
Phloem.

Question 31.
Write function of xylem.
Answer:
Conduction of water and minerals.

Question 32.
Name the peripheral and water proof dead tissue of old stem of woody trees.
Answer:
Cork.

Question 33.
What is source of cork?
Answer:
Cork is obtained from the stem of oak plant.

Question 34.
Name the protective tissue.
Answer:
1. Single layered epidermis
2. Cork

Question 35.
Name the only living cells of phloem.
Answer:
Phloem parenchyma.

Question 36.
What is the function of phloem?
Answer:
Pholem helps in conduction of food within the plant body.

Question 37.
Which kind of cells lack vessels in plants?
Answer:
Meristematic tissue.

Question 38.
What is the function of aerenchyma?
Answer:
Aerenchyma provide buoyancy to the aquatic plants.

Question 39.
Name the tissue which provide flexibility to plants.
Answer:
Collenchyma.

Question 40.
What is collenchyma?
Answer:
It is formed of thick-walled living cells which provide flexibility.

Question 41.
What is sclerenchyma?
Answer:
It is formed of cells with thick lignified cell wall.

Question 42.
Coconut fibres are formed of which tissue.
Answer:
Sclerenchyma.

Question 43.
What are stomata?
Answer:
Small pores in the epidermis of leaf.

Question 44.
What are guard cells?
Answer:
Stomata are enclosed by two kidney-shaped guard cell.

Question 45.
List two functions of stomata.
Answer:
1. Transpiration and
2. Exchange of gases.

Question 46.
What is epithelial tissue?
Answer:
Epithelial Tissue. Cells are arranged into single or multilayered sheet with no intercellular spaces.

Question 47.
What are two kinds of epithelium?
Answer:
1. Simple epithelium
2. Compound epithelium.

Question 48.
Write two functions of epithelium.
Answer:
1. Protection
2. Absorption of material and gases.

Question 49.
What is cartilage?
Answer:
It is a non-porous tissue in which intercellular matrix is abundant and composed of proteins with cells called chondroblasts.

Question 50.
What is connective tissue?
Answer:
Connective tissue connects or binds the similar or different kinds of tissue. Cells are scattered and intercellular spaces are filled with matrix.

Question 51.
Name the most abundant tissue found in the human body. Give its function.
Answer:
Connective tissue. It acts as packaging tissue.

Question 52.
Where is fat stored in the body?
Answer:
Fat is stored in adipose tissue found below the skin and around internal organs.

Question 53.
What is the colour of human blood?
Answer:
It is bright-red coloured when oxygenated and purple-red coloured when deoxy- genated.

Question 54.
Which blood corpuscles of human blood are involved in blood clotting at the injury?
Answer:
Blood platelets.

Question 55.
What is serum?
Answer:
Serum is blood plasma which lacks blood clotting proteins so cannot cause blood clotting.

Question 56.
Name three types of blood corpuscles.
Answer:
Erythrocytes (RBCs), Leucocytes (WBCs) and Blood platelets.

Question 57.
What are functions of RBCs?
Answer:
1. Transportation of oxygen as well as carbon dioxide.
2. pH constancy as haemoglobin acts as a buffer protein.

Question 58.
Give the function of lymph.
Answer:
Lymph acts as middle man so helps in exchange of materials between blood and body cells.

Question 59.
What is the life span of human RBCs?
Answer:
115-120 days.

Question 60.
Name the structural and functional units of nervous tissue.
Answer:
Neurons.

Question 61.
How is a nerve formed?
Answer:
Many nerve fibres bound together by connective tissue to form a nerve.

Question 62.
Name the two types of nerve processes of a neuron.
Answer:
Dendrites and Axon.

Question 63.
Name the components of blood.
Answer:

1. Plasma
2. RBCs
3. WBCs
4. Blood Platelets.

Question 64.
Name the minerals present in bones.
Answer:
Calcium and Phosphorus.

Question 65.
What is the function of ligament?
Answer:
Ligament connects bone with bone.

Question 66.
What is the function of tendon?
Answer:
Tendon connects bone with muscles.

Question 67.
Write location of cartilage.
Answer:
Ear lobes, tip of nose, wall of trachea.

Question 68.
What is the shape of smooth muscle fibres?
Answer:
Spindle-shaped.

Question 69.
Name the involuntary muscle fibres.
Answer:
Smooth muscle fibres.

Question 70.
Name the voluntary muscle fibres.
Answer:
Striped (skeletal) muscle fibre.

Question 71.
What is neuron?
Answer:
Neuron is the structural and functional unit of nervous tissue.

Question 72.
Give the location and function of cuboidal epithelium.
Answer:
In the germinal epithelium of gonads (testes and ovaries). Cells divide by meiosis to form gametes (sperms and ova).

Question 73.
Which type of epithelium is located in the mucosa of intestine?
Answer:
Columnar epithelium in which cells have microvilli.

Question 74.
What is the function of vascular tissue in plants?
Answer:
Vascular tissue conducts water and food from one part of plant to the other parts.

Question 75.
What is the advantage of dead cells in plants?
Answer:
Dead cells in plants provide structural strength and need less maintenance.

Question 76.
What is histology?
Answer:
Microscopic study of tissues is called histology.

Question 77.
What are unicellular organisms?
Answer:
Unicellular organisms. The body is comprised of one cell which performs all the functions.

Punjab State Board PSEB 10th Class Science Important Questions Chapter 7 Control and Coordination Important Questions and Answers.

PSEB 10th Class Science Important Questions Chapter 7 Control and Coordination

Long Answer Type Questions

Question 1.
Draw a well labeled diagram of the human brain and mention the functions of its various parts.
Answer:
Human brain is divided into three parts- Fore brain, mid brain and hind brain.
1. The Fore Brain: It is the largest part of the brain. It consists of the following parts :
(a) Olfactory lobes: They are concerned with sense of smell.
(b) Cerebrum: It is the most important and largest part of the fore brain. It is divided into two halves called the cerebral hemispheres. The two hemispheres are connected by a tract of nerve fibres called corpus callosum.

The functions of cerebrum are :

• It analyses the sensory signals in the association areas and thinking of a proper response.
• It sends response signals (motor signals) to the muscles through the motor areas.
• It stores memory of different experiences and uses this memory to generate proper responses.
• It is the seat of understanding language, memory, knowledge and logical thinking.

Section of human brain

(c) Thalamus: It is situated underneath (below) the cerebrum. Its function is to coordinate the incoming sensory signals to the cerebrum and outgoing motor signals from it.

• It controls many of the body’s important activities and feelings’ such as hunger, thirst, temperature regulation, sleep, emotional behaviour and sexual activity.
• It produces and secretes hormones that control the functioning of the pituitary gland situated just below it. It also controls the function of internal body organs by means of the autonomic nervous system.

2. The Mid Brain: It consists of crura cerebri and optic lobes. It is the topmost structure of the brain stem :

• It has centres relating to pain, temperature and touch.
• It controls many involuntary actions of the body.
• It has a collection of cells that control functioning of eyes and ears.

3. The Hind Brain: It consists of the pons, cerebellum and medulla oblongata :
(a) Pons. It is a bulging structure situated below the mid brain. It consists of large bundles of nerve fibres that interconnect different regions of the brain.

(b) Cerebellum. It is located at the lower back side of the brain under the cerebrum. Its functions are as follows :

• Maintaining the posture and balance of the body by controlling the muscles.
• It also controls the voluntary actions of the body by controlling motor signals coming from the cerebrum.

(c) Medulla oblongata. It is long stalk-like lowermost portion of the brain stem.. At the lower side it is connected with the spinal cord. It controls many involuntary actions such as salivation, vomiting, blood pressure, respiration and heart beat.

Question 2.
Describe the structure of spinal cord.
Answer:
The spinal cord extends from the foramen magnum where it is continuous with the medulla. It is a vital link between the brain and the body, and from the body to the brain. The spinal cord is 40 to 50 cm long and 1 cm to 1.5 cm in diameter. Two consecutive rows of nerve roots emerge on each of its sides. These nerve roots join distally to form 31 pairs of spinal nerves. The spinal cord is a cylindrical structure of nervous tissue composed of white and grey matter, is uniformly organized. The spinal nerve contains motor and sensory nerve fibres to and from all parts of the body.

Spinal Cord

Although the spinal cord constitutes only about 2% of the central nervous system (CNS), its functions are vital.
Knowledge of spinal cord functional anatomy makes it possible to diagnose the nature and location of cord damage and many cord diseases.

Question 3.
What is reflex action? Explain giving an example. What is reflex arc?
Answer:
Reflex action is a quick action in response without involvement of the thought process. It is controlled through the spinal cord in which transfer of impulse takes place from sensory neuron to the motor neuron. The path through which the signal travels during reflex action is called the reflex arc. As the reflex arc is a shorter route reflex action takes place in a fraction of a second. For example, if a person accidentally hits something on the leg, the pain receptors in the skin receive the pain and generate an electric signal. This impulse is sent by the sensory neuron to the spinal cord. In the spinal cord the impulse is transferred quickly to the motor neuron, which relays it to the leg muscles for quick action.

Question 4.
List the components of nervous system. What is a synapse? Explain what are its kinds.
Answer:

• Nervous system: It consists of central nervous system, peripheral nervous system and autonomic nervous system.
• Central nervous system: It consists of brain and spinal cord. It is the main controlling centre of the body.
• Peripheral nervous system: It consists of cranial and spinal nerves.
• Autonomic nervous system consists of a special set of peripheral nerves that innervate organs like heart, lungs, digestive tract.

Autonomic nervous system can be divided into two divisions :
(a) Sympathetic nervous system.
(b) Parasympathetic nervous system.

Synapse: Synapse is the close proximity of the axon of one neuron and the dendrite or cvton of another neuron with a gap. In a synapse, the transmitting cell is called the presynaptic cell, and the receiving cell is termed the postsynaptic cell. A narrow gap, called synaptic cleft, separates the presynaptic cell from the postsynaptic cell. Hence, an action potential occurring in the membrane of the presynaptic cell cannot be directly transmitted to the membrane of the postsynaptic cell.

Question 5.
What are phytohormones? Classify the main groups.
Answer:
Growth regulators: Growth is regulated not only by environmental factors like light and temperature but also by certain chemical substances within the plants. These substances are known as plant hormones, growth hormones, phytohormones or growth regulators. A plant hormone can be defined as a chemical substance, which is capable of translocation and regulating one or more physiological reactions, when present in low concentrations.

• Auxins
• Gibberellins
• Cytokinins
• Ethylene.
• Abscisic acid (ABA).

On the basis of their effect, phytohormones can be divided into two groups :
(а) Growth promoters: These stimulate the plant growth e.g. auxins, gibberellins, cytokinins and ethylene.
(b) Growth inhibitors: These inhibit or retard plant growth e.g. ABA.

Question 6.
Explain the following :
(i) Hydrotropism (ii) Thigmotropism (iii) Chemotropism.
Or
Explain briefly the various types of plant movements.
Answer:
Movements: Movements of plant parts can mostly be classified as growth movements and turgor movements. The growth movements are autonomic. The movements induced by external stimuli are called paratonic. Tropic movements can be of various types depending on the nature of external stimulus e.g. geotropism, thigmotropism, thermotropism, hydrotropism, chemotropism and phototropism.

Nastic movements are in the bifacial organ. Seismonastic movements are observed in Mimosa pudica.

• Phototropism: Movements towards stimulus of light.
• Geotropism: Movements towards stimulus of force of gravity.
• Hydrotropism: The term hydrotropism is applied to growth movements in response to external stimulus of water. Roots, normally or positively hydrotropic (i.e., they bend towards the source of water).
• Thigmotropism: Thigmotropism is the tropic movement in the plants due to the stimulus of touch, tactile, mechanical or rubbing.
• Chemotropism: When chemical substances are the external stimuli, the growth movement is termed as chemotropism. The best example is the growth of pollen tube through stigma and style towards the embryo sac with the stimulus of chemical substances present in the carpel.

Question 7.
Describe various endocrine glands.
Answer:
Endocrine glands and their secretions

Short Answer Type Questions

Question 1.
What are hormones? Why are they called chemical messengers? What are the general properties of hormones?
Answer:
Hormones: They are informational molecules secreted by the endocrine cells in one part of the body in response to changes in external or internal environment, and carried by blood to another part where they stimulate or inhibit specific physiological processes for the good of the body as a whole.

In other words, the hormones are chemical messengers that regulate the biological processes in the organisms as they carry the information in the form of chemicals.

General properties of hormones

• The hormones themselves do not create biochemical processes. They only modify the existing metabolic processes and change the rate of action.
• Hormonal actions are usually long lasting than those produced by nerve impulses.
• They are effective in minute quantities.
• They are secreted in response to specific stimuli.
• They are secreted independent of one another.

Question 2.
What is phototropism?
Answer:
Phototropism is the growth movement in response to unidirectional stimulus of light. It is observed in plant stem, root, leaves. Stem is positively phototropic.

Question 3.
Write differences between nastic and tropic movements.
Answer:

	Nastic Movements	Tropic Movements
1. Growth	growth independent movements	growth dependent movements
2.Time of Action	immediate	slow
3. Response to Stimulus	Non-directional	directional
4. Reason for action	change in turgor	cell division
5. Alternate name	nastics	tropism
6. Examples	folding of leaves of touch me- not(Mimosa), opening and closing of stomata	phototropism, geotropism, hydrotropism, chemotropism

Question 4.
Why is pituitary gland called master endocrine gland?
Answer:
Pituitary gland is a small pea-shaped endocrine gland situated inferior to hypothalamus. It is called master endocrine gland because its secretion control and regulates the secretions of all other endocrine glands.

Question 5.
Name one disorder each in case of less (hypo) or excess (hyper) secretion of insulin and thyroxine.
Answer:

Name of hormone	Disorder due to hvposecietion	Disorder due to hypersecretion
Insulin	Diabetes	Hyperglycemia
Thyroxine	Myxedema	Exophthalmic goitre

Question 6.
List four uses of auxins.
Answer:
Functions of IAA

• IAA brings about cell elongation.
• It initiates the formation and growth of roots and stem if applied to the cutting of stem.
• Application of auxins causes formation of seedless fruits.
• It has an inhibitory effect on abscission of leaves and fruits, which lead to leaf fall and fruit drop.
• The parthenocarpy can be induced by application of auxins.
• Respiration rate increases with auxins.

Question 7.
What are the physiological effects of gibberellins?
Answer:
Physiological effects of gibberellins :

• Gibberellins promote cell-division.
• Gibberellins promote cell-elongation.
• Gibberellins lead to increase in the length of internodes.
• Gibberellins induce parthenocarpy in many cases e.g. tomato.
• Gibberellins promote flowering in some plants like Chrysanthemum.
• Gibberellins prevent senescence in leaves.

Question 8.
What are the functions of cytokinins?
Answer:
Functions of cytokinins

• It promotes cell division by activating DNA synthesis.
• It promotes the growth of lateral buds by neutralising the auxin.
• It is reported that cytokinin activates protein synthesis in buds by incorporation of labelled amino acid.
• It is also found to be effective in removing the apical dominance.

Question 9.
Write short notes on abscisic acid and ethylene.
Or
Write functions of abscisic acid.
Answer:
Abscisic acid (ABA)

• Abscisic acid (ABA) is a growth regulator found widespread in plants. It is a growth inhibitor.
• Abscisic acid causes the inhibition of mitosis in the vascular cambium.
• As the winter approaches, the ABA brings about the dormancy of axillary buds.
• Abscisic acid also induces the dormancy in seeds.
• It causes ageing in leaves. It is also called ‘stress hormone’.

Question 10.
Write functions of Ethylene.
Answer:
Ethylene:
Ethylene is synthesized in the plants from amino acid methionine. Ethylene produces the effect on the growth of vegetative and reproductive parts of the plant.

Ethylene is the only gaseous phytohormone. It is basically a growth inhibitor and brings about the following functions in the plant body.

• Ethylene inhibits root growth and development of lateral buds.
• Ethylene inhibits the elongation of stem and stimulates its transverse expansion.
• The changes which occur during the ripening of fruit are also attributed to the effect of ethylene.
• Ethylene also accelerates the process of ageing in plant organs.

Question 11.
What is chemotropism?
Answer:
Directional movement of a plant/ or its parts in response to chemicals is called chemotropism e.g. growth of the pollen tube towards the ovule is a chemotropic movement due to which fertilization of flower takes place.

Question 12.
Give examples of geotropism.
Answer:

• 1.Roots move in the direction of gravity (positive geotropism).
• Shoots move (up) against direction of gravity (negative geotropism).

Question 13.
What is the type of phenomenon shown in the figure? Define the same.

Answer:

• Geotropism:
• Geotropism. It is a type of growth movements induced by stimulus of gravity.

Question 14.
Differentiate between hormones and enzymes.
Answer:
Differences between hormones and enzymes

Hormones	Enzymes
1. They are produced by glands which lack ducts (endocrines).	1. They are generally produced by glands which bear the ducts (exocrine).
2. They may be steroids, amines or protein in chemical nature,	2. They are always proteinic in nature.
3. They are consumed during metabolism.	3. They act as catalysts and are produced in the same quantity at the end of reaction.

Question 15.
Briefly explain the autonomic nervous system.
Answer:

• Autonomic nervous system: The autonomic nervous system coordinates the activities of viscera through the regulation of their smooth muscles and glands by its nerves.
• The sympathetic nervous system prepares the body to face an emergency by accelerating heart beat and breathing rate; dilating the bronchioles to facilitate gas exchange; and sending blood to the organs which need it most such as heart, brain and skeletal muscle for “fight or flight”. It releases neurotransmitters adrenaline and noradrenaline into the synapses (adrenergic).
• The parasympathetic nervous system acts when body is relaxing after an emergency. It restores heart beat and respiratory rate to normal and restarts digestion. It releases acetylcholine into the synapses (cholinergic).

Question 16.
List different parts of the human nervous system.
Answer:

Question 17.
Define ‘nerve impulse’. Which structure in a neuron helps to conduct a nerve impulse?
(i) towards the cell body?
(ii) away from the cell body?
Answer:
Nerve impulse: The information passing through neurons in the form of electrical and chemical signals is called nerve impulse. Neurofibrils in the neuron help to conduct impulses.

Neuron is structural and functional unit of nervous system.

• Dendrite carries the impulse to cell body.
• Axon carries impulse away from cell body.

Question 18.
Name the five major senses of man.
Answer:
Five major senses of man

1. Sense of hearing.
2. Sense of smell.
3. Sense of touch.
4. Sense of taste.
5. Sense of vision or sight.

Question 19.
Write short note on meninges present around brain. Name the fluid present in the spaces in between meninges. Mention its function.
Answer:
Meninges (Sing. Meninx.) The protective membranes present around brain. They are as follows :

1. Duramater: It is outer, thick, non-vascular membrane present inner to bones of cranium.
2. Piamater: It is inner, thin, vascular membrane present closely around brain.
3. Arachnoid membrane: It is the middle membrane.
4. Cerebrospinal fluid is present in between the meninges. It protects brain from mechanical shock.

Question 20.
Label the parts of human brain.

Answer:
A. Cerebrum
B. Cerebellum
C. Medulla oblongata.

Question 21.
What is a gland? Name the two types of glands.
Answer:
Definition: A cell, a tissue, or an organ which secretes certain useful chemical compounds required for particular function is called a gland.

Types: Animals have two types of glands: exocrine and endocrine.

Question 22.
How does our body maintain blood sugar level?
Answer:
The timing and amount of hormone released are regulated by feedback mechanisms.
When the sugar levels in blood rise, they are detected by the cells of the pancreas which respond by producing more insulin. As the blood sugar level falls, insulin secretion is reduced.

Question 23.
Why is pancreas a dual gland?
Answer:
Pancreas is a dual gland because it acts as both endocrine and exocrine gland. As endocrine it secretes hormones like insulin, glucagon. As an exocrine gland, it releases enzymes like trypsin, lipase, amylase etc. Such types of glands are also called heterocrine glands.

Question 24.
List the functions of testosterone and estrogen.
Answer:

• Functions of testosterone: Develops male reproductive organs and secondary sexual characters in males.
• Functions of estrogen: Develops female genital organs and secondary sexual characters in females.

Question 25.
Name the hormones which stimulate the testis.
Answer:

• Follicular Stimulating Hormone (FSH). It stimulates the production of sperms in the testis.
• Interstitial Stimulating Hormone (ISH). It stimulates the interstitial cells of the testis and produce a male sex hormone known as ‘testosterone’.

The FSH and ISH are secreted by pituitary gland.

Question 26.
List some of the functions of adrenal glands.
Answer:
Functions of adrenal glands

• Prepare the body for emergencies.
• Regulate the kidney in maintaining salt and water balance.
• Control blood pressure and pulse rate.
• Control concentration of sodium, potassium and sugar in the body.
• Control some sexual characteristics.
• Influence breakdown of tissue proteins into amino acids.

Question 27.
Write a note on turgor movements.
Or
Mechanism of movements shown by Mimosa pudica, if touched.
Answer:
Turgor movements. Mimosa pudica (Touch-me-not) shows typical seismonastic type of movements. It is a paratonic variation type of movement which is brought about in response to external stimulus of touch. Leaf of Mimosa pudica is a compound leaf. It shows pulvini of primary and secondary order of petioles and sub-petioles. It gives a very quick response to a shock stimulus.

Question 28.
How do phototropism differ from geotropism?
Answer:
Differences between phototropism and geotropism

Phototropism	Geotropism
1. Response of parts of plants in the form of growth movement to the stimulus of light is called phototropism.	1. It applies to growth movements induced by stimulus of force of gravity.
2. Stem and aerial parts bend towards light source.	2. Stem and aerial parts move away from force of gravity.
3. Roots and other underground parts move away from source of light.	3. Roots and other underground parts move towards the force of gravity.

Question 29.
List the major endocrine glands and state their position in the human body.
Answer:
The major endocrine glands in the human body are:

• Pituitary gland
• Thyroid gland
• Parathyroid gland
• Thymus gland
• Islets of Langerhans present in Pancreas
• Adrenal gland
• Testis
• Ovary
• Pineal Gland.

Endocrine glands in human (a) male (b) female

Question 30.
Nervous and hormonal system together perform the function of control and co-ordination in human beings.” Justify the statement.
Answer:
Nervous and hormonal system. Both nerves and hormones transmit information between different parts in the animal body, in the same manner (chemical communication). Both coordinate and regulate physiological activities of the organisms. Moreover, there is a considerable coordination between the two. Synthesis and release of some hormones are regulated by nerves. On the other hand, hormones may also influence the activation of nerves. Because of their interrelationship, the nervous and the endocrine system are now together referred to as the neuroendocrine system.

Question 31.
What are the general functions of ‘hormones’?
Answer:
Functions of Hormones

• Hormones stimulate the tissue activity.
• Hormones regulate growth and reproduction.
• Hormones control metabolism.
• Hormones synthesize, store and utilize substances like glucose.
• Hormones conserve water and minerals.

Question 32.
Label 1 and 2 in the figure given below:

Answer:
1. Ovary
2. Neck showing location of Thyroid.

Very Short Answer Type Questions

Question 1.
Are movements in living organi-sms a characteristic of life?
Answer:
No.

Question 2.
Movements in plants are due to result of which kind of action?
Answer:
Growth.

Question 3.
Crying, respiration and voluntary movements are linked to which category.
Answer:
Involuntary actions.

Question 4.
Name the structural and functional unit of nervous system.
Answer:
Neuron.

Question 5.
What is the function of dendrites?
Answer:
Dendrites acquire the information.

Question 6.
Name the structure of neuron which conduct impulse.
Answer:
Axon.

Question 7.
Name the sites where electrical impulses are conducted into hemical impulses.
Answer:
Synapse.

Question 8.
What is a neuron?
Answer:
Neuron: It is a structural and functional unit of nervous system. It is the largest cell of the body.

It has three components i.e.

1. cell body
2. dendrites
3. axon.

Question 9.
What is synaptic cleft?
Answer:
The gap between dendrites of one neuron and axon of the next neuron is called synaptic cleft.

Question 10.
Mention the receptors for light and sound in animals.
Answer:

• Receptors for light. Photore-ceptors (Eyes)
• Receptors for sound. Phonoreeeptors (Ears)

Question 11.
What is reflex action?
Answer:
Reflex action: It is sudden spontaneous, mechanical, involuntary response to a stimulus by voluntary organs.

Question 12.
Give two examples of reflex action.
Answer:

1. Closing of eyes in response to bright light.
2. Withdrawal of hand in case touched a hot plate.

Question 13.
Which organ is involved in reflex action?
Answer:
Spinal cord.

Question 14.
Name three parts of neurons in complex reflex arc.
Answer:
A complex reflex arc is composed of afferent, connector and efferent neurons.

Question 15.
Name the main constituents of central nervous system.
Answer:
Brain and spinal cord.

Question 16.
What are the components of peripheral nervous system?
Answer:
Cranial (cerebral) nerves and spinal nerves originating from brain and spinal cord respectively.

Question 17.
Name the three main parts of brain.
Answer:
Fore brain, Mid brain and Hind brain.

Question 18.
List three involuntary actions.
Answer:
Circulation of blood, secretion of saliva and movement of food in the alimentary canal.

Question 19.
Involuntary actions are cont-rolled by which part of brain.
Answer:
Medulla.

Question 20.
Cycling, walking along a straight path and picking up of pencil are controlled by which part of brain.
Answer:
Cerebellum of hind brain.

Question 21.
Name the part of brain which control balancing and voluntary movements of body.
Answer:
Cerebellum of hind brain.

Question 22.
What is the function of cerebro spinal fluid?
Answer:
CSF (cerebrospinal fluid) acts as a shock absorber.

Question 23.
Name the structure which protects spinal cord.
Answer:
Vertebral column.

Question 24.
How does plant cell change its shape?
Answer:
Change in the water content of plant cell.

Question 25.
What is the function of tendril.
Answer:
Tendril helps in climbing along a support.

Question 26.
Name the hormone which help in cell division.
Answer:
Cytokinin.

Question 27.
Name the hormone secreted by adrenal gland.
Answer:
Adrenaline.

Question 28.
Where is thyroxine hormone secreted?
Answer:
Thyroid gland.

Question 29.
Name the hormone which plays role in metabolism of carbo-hydrates, proteins and fats.
Answer:
Thyroxine hormone.

Question 30.
Name the gland which secreted growth hormone.
Answer:
Pituitay gland.

Question 31.
Name the hormones which play role in maturity during adolescence in boys and girls.
Answer:
Testosterone in boys and estrogen in girls.

Question 32.
Where is insulin secreted?
Answer:
Pancreas.

Question 33.
In addition to nervous system, which other system plays role in coordination.
Answer:
Endocrine system which secretes chemical messengers called hormone.

Question 34.
Name the hormone which helps in chemical co-ordination in plants.
Answer:
Phytohormone (plant hormones).

Question 35.
What is the main element of thyroxine hormone?
Answer:
Iodine.

Question 36.
What is the main function of the vasopressin hormone?
Answer:
Regulates water content in the blood.

Question 37.
Write the function of hormone ‘thyroxine’ in our body.
Answer:
It regulates metabolism of carbo-hydrates, fats and proteins.

Question 38.
Which two systems of body work together for control and coordination of body parts?
Answer:
Nervous system and Hormonal system (endocrine glands).

Question 39.
Which organ secretes a hormone when the blood sugar rises. Name a digestive enzyme released by this organ.
Answer:

1. Pancreas releases insulin hormone.
2. Trypsin enzyme.

Question 40.
Define endocrine glands.
Answer:
These glands are ductless glands which secrete chemical messengers called hormones carried by blood to target organs.

Question 41.
Name the hormone which inc-reases blood pressure and rate of heart beat.
Answer:
Adrenaline.

Question 42.
Name the female sex hormones.
Answer:

• Progesterone
• Oesterogen
• Estardiol.

Question 43.
Name the following :
(i) The cause of diabetes mellitus.
Answer:
Deficiency of insulin

(ii) The two portions of adrenal gland.
Answer:
Adrenal cortex and adrenal medulla

(iii) The gland which function actively in emergency situations.
Answer:
Adrenal medulla

(iv) The hormone of pituitary that helps in child birth.
Answer:
Oxytocin

(v) The endocrine gland located on the top of kidneys.
Answer:
Adrenal gland

(vi) The gland which secretes insulin.
Answer:
Pancreas.

Question 44.
Name the following :
(i) The hormone which prepares the body to meet any emergency situation.
Answer:
Adrenaline

(ii) An example of the disease caused due to insufficient secretion of hormone.
Answer:
Cretinism

(iii) The gland, which produces the so called ‘emergency hormone’.
Answer:
Adrenal gland

(iv) Carrier of hormones from the gland to target organ.
Answer:
Blood

(v) The hormone which controls (i.e. reduces) the level of sugar in blood, and the gland which secretes it.
Answer:
Insulin, Pancreas.

Question 45.
Name the three kinds of neuron.
Answer:

1. Motor neuron
2. Sensory neuron
3. Relaying neuron.

Question 46.
What happens when bright light is focussed on eyes?
Answer:
Eyes get closed in response to light so as to protect the eyes.

Question 47.
Where are receptors located in the body?
Answer:
Sense organs.

Question 48.
What is the function of gustatory receptors?
Answer:
To taste the food.

Question 49.
Name the organs concerned with sense of smell.
Answer:
Olfactoreceptor.

Question 50.
Which part of plant bends towards light?
Answer:
Shoot apex.

Question 51.
Name the largest cell present in human body.
Answer:
Neuron.

Question 52.
What are the three basic regions of the brain?
Answer:

1. Fore brain
2. Mid brain
3. Hind brain.

Question 53.
Which part of the brain controls the heart?
Answer:
Medulla oblongata.

Question 54.
Name the following :
(i) Structural and functional units of the nervous system.
Answer:
Neurons

(ii) Two type of peripheral nerves.
Answer:
Cranial and spinal nerves

(iii) Most important part of the nervous system.
Answer:
Brain

(iv) Three divisions of human brain.
Answer:
Fore brain, mid brain and hind brain

(v) Largest part of the brain.
Answer:
Cerebrum

(vi) Two types of matter present in brain and spinal cord.
Answer:
White matter and grey matter.

Question 55.
How many hormones are secreted by pituitary gland?
Answer:
13 Types of hormones are secreted by pituitary gland.

Multiple Choice Questions

Question 1.
Which of the following is not a plant hormone?
(A) GA3
(B) Ethylene
(C) Phytochrome
(D) Auxins.
Answer:
(C) Phytochrome

Question 2.
Cytokinins stimulate the cell for:
(A) Turgor
(B) Elongation
(C) Cell division
(D) Wall thickening
Answer:
(C) Cell division

Question 3.
Movement in the leaf of the Touch-me-not (Mimosa) plant is:
(A) Epinasty
(B) Hyponasty
(C) Nyctinasty
(D) Seismonasty.
Answer:
(D) Seismonasty.

Question 4.
Hydrotropism is response towards:
(A) light
(B) touch
(C) gravity
(D) water.
Answer:
(D) water.

Question 5.
The reflex action is :
(A) blinking of eyelid
(B) swallowing of food bolus
(C) sneezing and coughing
(D) All the above.
Answer:
(D) All the above.

Question 6.
Nerve fibres transmit the nerve message by means of :
(A) chemical
(B) physical
(C) electrochemical
(D) electrical.
Answer:
(C) electrochemical

Question 7.
Brain and spinal cord act as :
(A) Receptors
(B) Effectors
(C) Modulators
(D) None of these.
Answer:
(A) Receptors

Question 8.
Which of the following is not a structure in the hind brain?
(A) Medulla oblongata
(B) Thalamus
(C) Cerebellum
(D) Pons.
Answer:
(B) Thalamus

Question 9.
Which one of the following endocrine gland produces two distinct hormones?
(A) Adrenal
(B) Thymus
(C) Testis
(D) Pineal.
Answer:
(A) Adrenal

Fill in the Blanks :

Question 1.
The nervous system uses ______ impulses to transmit messages.
Answer:
electrical.

Question 2.
______ is the main coordinating centre in the body.
Answer:
Brain.

Question 3.
The movement of a part of a plant in response to light is called ______
Answer:
Phototropism.

Question 4.
Endocrine glands secrete ______ into blood.
Answer:
Hormones.

Question 5.
Insulin hormone is secreted by ______
Answer:
Pancreas.

Question 6.
Auxins play role in cell ______
Answer:
Elongation.

Question 7.
In human there are ______ pairs of cranial nerves.
Answer:
Twelve.

Question 8.
______ is the junction between two adjacent neurons.
Answer:
Synapse.

Punjab State Board PSEB 9th Class Science Important Questions Chapter 5 The Fundamental Unit of Life Important Questions and Answers.

PSEB 9th Class Science Important Questions Chapter 5 The Fundamental Unit of Life

Long Answer Type Questions

Question 1.
Describe the structure of the plant cell.
Answer:
A generalized plant cell consists of three distinct parts viz, cell wall, cell membrane or plasma membrane and protoplasm.
1. Cell wall. It is the outermost covering of a cell made up of a non-living substance called cellulose. Is is permeable. It provides shape, strength and protection to cell.

2. Cell membrane or Plasma membrane. It is thin, delicate and elastic protoplasmic covering lying internal to the cell wall. The plasma membrane controls the entrance and exit of molecules and ions.

3. Cytoplasm. It consists of a number of living and non-living structures. The living structures are called cytoplasmic organelles or cell organelles and include structures like endoplasmic reticulum, ribosomes, golgi apparatus, mitochondria, lysosomes, plastids, vacuoles etc.
(a) Plastids. Plastids are spherical or discoid bodies containing different types of pigments in them. They are of three types viz. chloroplasts, chromoplasts and leucoplasts. The chloroplasts contain a green pigment in them, called chlorophyll. They play a vital role in the process of photosynthesis. The chromoplasts contain pigments other than chlorophyll. They impart various colours to flowers and fruits. Leucoplasts are colourless plastids. They are concerned with the storage of starch.
(b) Mitochondria are power house of cell.
(c) Ribosomes are of 70 S type. They are site for protein synthesis.
(d) Endoplasmic reticulum is network of membranes.
(e) Vacuoles. These are fluid-filled bubble-like structures bounded by a membrane, called tonoplast. They are mostly found in plant cell. Vacuoles provide turgidity and rigidity to cell.

4. Nucleus. It is a dense spherical body bounded by a membrane, called nuclear membrane. Embedded within the nuclear sap are found a number of thread-like structures called chromosomes with genes on them. The nucleus controls the various metabolic activities of the cell.

Question 2.
Draw a well labelled diagram of ultrastructure of plant cell.
Answer:
Ultrastructure of plant cell

Question 3.
Describe the structure of nucleus. Write its functions.
Answer:
A true nucleus is present in all the eukaryotic cells except mammalian RBCs, sieve tube cells, tracheids and vessels. It directs life processes of cells. It is formed of four components:
(a) Nuclear membrane. It is a two-layered envelope around the nuclear sap. It is porous (with nuclear pores) and semipermeable membrane. Outer membrane is studded with ribosomes and may be continuous with RER. It regulates exchange of materials between nucleoplasm and cytoplasm.

(b) Nucleoplasm. It is a semifluid colloidal substance in which nucleoli and chromatin fibres are present.
(c) Nucleolus. It is dense, spherical, naked and darkly stained structure and is the site of formation and storehouse of rRNAs.
(d) Ovomatin fibres. These are long, fine and darkly stained threads which collectively form nuclear reticulum. During prophase of mitosis and meiosis, these condense to form a species-specific number of rods, called chromosomes. These are with genes which are chemically formed of DNA and act as units of heredity and variations.
Functions of the nucleus:
The nucleus performs the following important functions:

• The nucleus controls all the cellular activities of the cell.
• Tire nucleus plays an important role in transmission of hereditary characters from parents to offsprings.
• The nucleus plays a vital role in cell division.

Question 4.
Write short notes on:
(a) Chloroplast
(b) Endoplasmic reticulum
(c) Golgi bodies
Answer:
Structure and functions of a chloroplast:
A chloroplast is formed of two membranes and two chambers, so resembles a mitochon-drion. Outer membrane is freely permeable while inner membrane is semi permeable. Inner chamber is filled with a denser and granular proteinaceous (about 50%) ground substance called stroma or matrix. It is site of dark reaction or CO₂ fixation of photosynthesis and has a number of grana, 70 S ribosomes and DNA molecules (circular and naked).
1. Grana are site for light reactions of photosynthesis.
2. Function of Chloroplasts: These are sites of photosynthesis, so are called “kitchens of cell.”

(b) Endoplasmic reticulum
There are two forms of endoplasmic reticulum. They are the following:

• Rough type (RER): Ribosomes are associated with rough endoplasmic reticulum.
• Smooth type (SER): Golgi apparatuses are associated with smooth endoplasmic reticulum.

Components of ER

Functions of Rough and Smooth Endoplasmic reticulum

Functions of Endoplasmic Reticulum:

1. The endoplasmic reticulum acts as secretory, storage, circulatory and nervous system of the cell. Its functions depend upon its location, nature and cell type.
2. It provides an ultrastructural skeletal framework of the cell.
3. ER provide channels for quick transport of materials.
4. It provides surface for attachment of ribosomes.
5. It provides materials, lipids and proteins for biogenesis of membranes.

Functions of Smooth Endoplasmic Reticulum:

1. Detoxification of drugs and poison.
2. Formation of visual pigment from Vitamin A in retinal cells.
3. Synthesis of fats inside the cells of adipose tissue.
4. Synthesis of steroids and hormones.

(c) Golgi complex or Golgi Apparatus:
The golgi complex is usually located near the cell nucleus and in animal cells it is frequently disposed around the centriole pair. It normally consists of numerous sets of membrane-bound, smooth surface cisternae. Each cisterna is flat, disc-shaped and curved like a shallow bowl.

It has lumen which is bounded by a single membrane. Each set of flattened disc-shaped cistemae forms a structure that resembles stack of plates, called a Golgi stack or dictyosome (as referred in the plants).

Question 5.
Discuss the structure and function of mitochondrion.
Answer:
Structure. Mitochondria are ‘power house’ of cells. It has two mitochondrial membranes and two chambers. Outer mitochondrial membrane is smooth and porous while inner mitochondrial membrane is produced into finger-like processes called cristae to increase the surface area for the distribution of respiratory enzymes of electron transport chain.

Cristae are studded with regularly placed knob-like oxysomes which take part in energy releasing reactions. Inner chamber is filled with a granular matrix having respiratory enzymes. Matrix present in inner chamber also contains DNA, RNA and ribosomes.

Functions of mitochondria:

1. These are called power houses or power plants or ATP mills as these are site of aerobic oxidation (cellular respiration) of glucose to produce energy-rich ATP molecules.
2. They provide biological intermediates for the synthesis of various biomolecules such as fatty acids, amino acids, steroids etc.

Question 6.
Write a note on prokaryotic cell.
Answer:

1. The prokaryotes have a single membrane.
2. Cells which have respiratory enzymes associated with plasma membrane.
3. Circular DNA without proteins, forming a single prochromosome called nucleoid and lying in direct contact with cytoplasm.
4. They have 70 S ribosomes.
5. They lack membrane-bound organelles and sap vacuoles.
6. They do not show cyclosis, phagocytosis, pinocytosis and exocytosis.
7. Cell division by fission or budding.
8. Examples. Bacteria, Blue green algae and Mycoplasma.

Question 7.
Write a short note on eukaryotic cell.
Answer:

1. The eukaryotic cells have double membrane and plasma membrane devoid of respiratory enzymes.
2. These cells have linear DNA associated with proteins forming two to many chromosomes enclosed by a nuclear envelope. Thus proper well defined nucleus is present.
3. There are present 80 S ribosomes.
4. Many membrane-bound organelles such as mitochondria, chloroplasts, lysosomes etc., and sap vacuoles present.
5. Form mitotic apparatus in cell division and undergo meiosis.
6. They may show cyclosis, phagocytosis, pinocytosis and exocytosis.

Question 8.
Draw the ultrastructure of a typical animal cell.
Answer:
An animal cell has three functional regions. Plasma membrane, cytoplasm and nucleus.

Short Answer Type Questions

Question 1.
What is cell and cell theory?
Answer:
Cell. 1. Structural and functional unit of life is called cell.
2. A cell is mass of protoplasm formed of different types of inorganic and organic biomolecules and externally bounded by a thin and semipermeable plasma membrane.
Cell Theory. M.J. Schleiden and Theodore Schwann (1938-39) proposed cell theory. The cell theory can be stated as follows:
(a) The body of all living organisms is composed of cells. Cell is a unit of structure and function of life.
(b) New cells are formed from the pre-existing cells only (R. Virchow).
(c) The life is passed from one generation to the next generation through a single cell.

Question 2.
What is a prokaryotic cell?
Answer:
Prokaryotic cell, (pro = primitive, karyon = nucleus) It is characterized by an incipient nucleus called nucleoid formed of single and circular chromosome. It is formed of double-stranded DNA but not associated with histone proteins. It is not enclosed by nuclear membrane.

• Membrane-bound cell organelles such as mitochondria, chloroplasts etc. are absent.
• Examples: Bacteria, Blue-green algae, Mycoplasma etc.

Question 3.
What is a eukaryotic cell?
Answer:
A eukaryotic (eu = good; karyon = nucleus) cell has true nucleus which has two or more linear chromosomes lying in the nucleoplasm and is surrounded by a double and porous nuclear membrane. Membrane bound organelles present. 80 S Ribosomes present (S = Svedberg unit).

Question 4.
Explain structural and functional organisation of unicellular and multicellular organism.
Answer:

• Unicellular organism, in such organisms, a single cell carries out all life processes with the help of organelles. They are also called acellular organisms.
• Multicellular organism. A multicellular organism is made up of large number of cells.
• The cells are differentiated to share varied functions performed by unicellular organisms. Whatever the case may be, all multicellular organisms start their life from a single cell.
• The multicellular organism represents itself in two forms – as an individual and as a member of assembly of cells.
• Advantages of Multicellularity:
  • The division of labour in a multicellular organism increases the efficiency of the organism.
  • It promotes the chance of survival.

Question 5.
What do you mean by:
1. Organelle
2. Inclusions
Answer:
1. Organelle, it is a living structure of cell with a specific function.
2. Inclusions. The lifeless structures in a cell, which may or may not have a definite function are called inclusions. These are vacuoles, excretory products, starch grains etc.

Question 6.
Distinguish between cell wall and cell membrane.
Answer:
Differences between cell wall and cell membrane

Cell wall	Cell membrane
1. It is present only in plant cells where it lies outside the cell membrane. 2. Dead in nature and permeable. 3. Composed of cellulose. 4. It is thick in nature.	1. It ocurs in animal cells and plant cells. 2. Living membrane and is semi-permeable. 3. Composed of lipids and proteins. 4. Comparatively very thin.

Question 7.
Name the two nucleic acids present in cell.
Answer:

• DNA (Deoxyribose nucleic acid): It is the genetic material. It is passed on from parents to next generation, It regulates the functioning of cells.
• RNA (Ribose nucleic acid): It is structural component of ribosome. It plays role in protein systhesis.

Question 8.
Why are mitochondria called “power house of cell”?
Answer:
Mitochondria are site of generation, transport and storage of ATP. Adenosine triphosphate (ATP) is the energy currency of the cell.

Question 9.
Explain lysosomes.
Answer:

• Lysosomes. They are single membrane bound vescicular structures. They are present in cytoplasm of eukaryotic cells. They contain digestive enzymes.
• They exist in four different forms thus exhibit polymorphism.
• They are involved in autolysis and hence called as ‘suicidal bags.’

Question 10.
List the functions of vacuoles.
Answer:
Functions of vacuoles

1. They act as storage sacs for solid or liquid contents of cell.
2. They help the cell to remain turgid and rigid.
3. Vacuoles play an important role in growth.
4. In some freshwater unicellular organisms, specialised vacuoles play an important role in expelling excess water and some wastes from, cells. It is called osmoregulation.

Question 11.
What is centrosome? List two functions of centrosome.
Answer:
Centrosome: It consists of granule like two centrioles; surrounded by clear area of cytoplasm called centrosphere. It is present in animal cells only.
Functions of centrosome:

• They help in spindle formation during cell divison in animal cell.
• They act as basal bodies and give rise to motile structures, i.e. cilia and flagella.

Question 12.
Differentiate smooth endoplasmic reticulum (SLR) and rough endoplasmic reticulum (RER).
Answer:
Differences between SER and RER:

SER	RER
1. It does not bear ribosomes over the surface of its membranes which are smooth. 2. It is engaged in the synthesis of glycogen, lipids and steroids. 3. It gives rise to sphaerosomes.	1. It possesses ribosomes attached to its membranes which are rough. 2. The reticulum takes part in the synthesis of proteins and enzymes. 3. It helps in the formation of lysosomes through golgi apparatus.

Question 13.
What are ribosomes? Write their kinds and chemical composition.
Answer:
Structure of Ribosome. The ribosomes are ribonucleoproteinic, obovate, spheroid without membrane structures. They are having two sub-units, one is larger sub-unit having dome-shaped structure and the other smaller sub-unit forming a cap-like structure. They are composed of ribosomal RNA (rRNA) and proteins.
Type of ribosomes:
1. 70 S ribosomes. They are present in both prokaryotic and eukaryotic cell.
2. 80 S ribosomes. They are present in eukaryotic cell.

Functions of ribosomes:
They are the site of protein synthesis as they contain enzymes involved in protein synthesis.

Question 14.
Write functions of cell wall.
Answer:
Functions of cell wall:

1. It provides shape and rigidity to the cell
2. It protects the protoplast.
3. It permits cells of bacteria, fungi and plants to withstand very dilute external environment without bursting.
4. It increases the size of cell by continuous absorption.
5. It is involved in the movement of materials in and out of the cell.

Question 15.
Give the functions of plasma membrane.
Answer:
Functions of plasma membrane:

1. It maintains individuality of cells.
2. It provides shape to the cell.
3. It keeps the cell contents in place and distinct from the environmental materials.
4. It protects the cell from injury.
5. It regulates the flow of material into and out of the cell. It allows only the selected substances to move across it.
6. It forms organelles of cell.

Question 16.
Define the following:

1. Cytoplasm
2. Hyaloplasm
3. Nucleoplasm.

Answer:

1. Cytoplasm: The clear, translucent, colourless, viscous, fluid in which are present various cell inclusions and organelles is called cytoplasm.
2. Hyaloplasm: The clear homogeneous ground substance of cytoplasm is termed hyaloplasm (cytoplasmic matrix).
3. Nucleoplasm: Clear transparent homogeneous fluid inside the nucleus is called ucleoplasm.

Question 17.
State the differences between cilia and flagella.
Answer:
Differences between cilia and flagella:

Cilia	Flagella
1. They are short hair-like structures with an average length of 5-10 mm. 2. They are present all over the surface of cell of the organism. 3. They are more in number usually 100 to a few thousand per cell. 4. They beat perpendicularly and simultaneously. 5. The cilia produce a sweeping or pendular stroke.	1. They are long, whip-like structures with an average length of 150 mm. 2. They are usually present on one end of cell. 3. They are less in number usually 1 or 2 per cell. 4. They beat freely. 5. The flagella produce undulatory motion.

Question 18.
State the differences between grana and stroma.
Answer:
Differences between grana and stroma:

Grana	Stroma
1. It consists of flatfened sac-like structures which are piled up one above the other like stacks of coins. 2. They contain photosynthetic pigments on them. 3. They are made of lipoproteins.	1. It is matrix or ground substance of chloroplast in which different structures like grana and lamellae are embedded. 2. Pigments are absent. 3. It is composed of watery proteinaceous substance.

Question 19.
Write functions of cell wall.
Answer:
Function of cell wall:

1. It protects the cell from mechanical damage and infection.
2. It helps in cell-to-cell interaction.
3. It acts as a barrier to unwanted molecules.
4. It provides rigidity and mechanical support to the cells.

Question 20.
How will you examine cells of onion peel.
Answer:
Examination of Onion Feel

1. Take out the onion peel from the inner side of the scale of the bulb.
2. Put this transparent peel into water and cut a small piece.
3. Stain it with safranin solution. It will make the nucleus more distinct.
4. Put it on the slide and place it in glycerine.
5. Observe under low power microscope, then change it to high power and study the following:

Observation:

• Regular, rectangular-shaped cells are placed close to each other.
• Cell has a prominent cell wall, cytoplasm and nucleus. The vacuole occupies the central position.

Question 21.
What are possible shapes of cells? Explain with simple sketches.
Answer:
Shapes of cells

1. Shapes of the cells differ not only in different organisms but also in different parts of same organism. They may be oval, spherical, discoid, cuboidal, columnar, spindle-shaped etc.
2. The shape of the cell is usually related with its function.
3. Some other factors controlling the shape of cell are function, age, pressure, cell wall and internal or external skeleton.
4. Amoeba and leucocytes go on changing their shapes to enable them to engulf the materials.

Question 22.
Differentiate between diffusion and osmosis
Answer:
Differences between diffusion and osmosis:

Diffusion	Osmosis
1. Diffusion is the net downward movement of a given substance (ions, atoms or molecules, etc.) along the free energy gradient from the place of its higher concentration to an area of its lesser concentration. 2. The diffusion may occur in any medium and the diffusing particles may be solid, liquid or gas. 3. Presence of semipermeable membrane is not required.	Osmosis is a special type of diffusion of solvent molecules from low concentration of solution to higher concentration of solution when the two are separated by a semipermeable membrane. 2. The osmosis occurs in liquid medium and only the solvent molecules move from one place to another. 3. Presence of semi-permeable membrane in between the two solutions is required.

Question 23.
Which organelle is called as protein factory of the cell?
Answer:
Ribosomes provide space for the synthesis of proteins in the cell. Hence, they are called protein factories. It synthesises various proteins and enzymes for the cell. Haemoglobin is an example of a protein made by free ribosomes in the young red blood corpuscles.

Question 24.
Differentiate Ribosome and Lysosome.
Answer:
Differences between ribosome and lysosome:

Ribosome	Lysosome
1. Ribosome is an oval to rounded granular structure which is not covered ever by any membrane. 2. It consists of two unequal nucieoprotein subunits. 3. It takes part in protein synthesis.	1. Lysosome is a rounded membrane lined vesicle containing number of hydrolytic enzymes. 2. It does not consists of nucieoprotein. 3. It takes part in digestion, scavenging and defence against pathogens.

Question 25.
What are plastids? Name its three types.
Answer:
Plastids. These are double membrane bound organelles found in plant cell. These are of three types:

• Chromoplasts
• Chloroplasts
• Leucoplasts.

Question 26.
Write functions of plastids.
Answer:
Functions of plastids

1. Chloroplasts are the site of photosynthesis so called as kitchen of the cell.
2. Chromoplasts provide colour to flowers and fruits.
3. Leucoplasts are site of storage of food.
4. Granum is site of light reaction, while stroma is the site of dark reaction.

Question 27.
What are the functions of lysosomes?
Answer:
Functions of lysosomes:

1. Take part in intracellular digestion of foreign particle.
2. They provide energy during starvation.
3. They help in defence against bacterial and viral infection.
4. Lysosome removes cellular debris.

Question 28.
Name the various organelles of cell and mention the most important function of each.
Answer:
Names and functions of cellular organelles:

Name of cell organelle	Function
1. Plasma membrane	Protects the cell organelles and separates the contents of cell from external environment.
2. Cell wall (plant cell only)	Provides strength and rigidity to the cell. It permits the bacterial and plant cells to withstand very dilute external medium without bursting.
3. Cytoplasm	Contains machinery and metabolites for carrying out the instructions sent from nucleus.
4. Cytoplasmic matrix	Contains raw materials and enzymes for metabolism.
5. Endoplasmic reticulum	It is responsible for transportation of extracellular and intracellular chemical molecules. It is also the site for synthesis of various molecules.
6. Ribosomes	These are sites for protein synthesis.
7. Golgi complex	Complexing, packaging and dispatching various materials to various targets inside and outside the cells.
8. Mitochondria	Site for respiratory reactions and energy liberation in the form of ATP.
9. Lysosomes (animal cells only) Centrosome (animal cells only) Plastids (plants only). Cilia and flagella. Vacuoles. Nucleus.	Helps in waste disposal system and autolysis. Forms spindle during cell division. Responsible for photosynthesis. Provide movement to cell. Storage sacs for liquid and solid contents. Regulates growth and reproduction of cell.

Question 29.
Differentiate cytoplasm and nucleoplasm.
Answer:
Differences between cytoplasm and nucleoplasm

Cytoplasm	Nucleoplasm
1. Part of protoplasm that lies outside	1. Part of protoplasm that lies inside the
2. It appears to be homogeneous semi-fluid jelly-like substance	2. It is transparent.
3. It contains number of inorganic substances forming clear true solution and organic substances lipids, protein and carbohydrates forming a polyphasic colloidal system.	3. Nucleoplasm is colloidal substance having similar composition to cytoplasm, but contains more of nucleo- tides.
4. Suspended in it are various organelles and inclusions.	4. Suspended in it is chromatin.

Question 30.
What will happen to a cell if its nucleus is removed?
Answer:
Cell will die with passage of time as nucleus is the controlling centre of all functions of cell.

Very Short Answer Type Questions

Question 1.
What is the structural and functional unit of life?
Answer:
Cell.

Question 2.
Name three functional regions of a cell.
Answer:

• Plasma membrane
• Nucleus
• Cytoplasm.

Question 3.
Name the orgnelles present in the cells.
Answer:
Mitochondria, Ribosomes, Endoplasmic Reticulum, Golgi bodies, Centrosome, Lysosomes, Plastids.

Question 4.
Name the organelle present in plant cell only.
Answer:
Plastids.

Question 5.
What is the main component of nucleus?
Answer:
Chromatin network which takes up the shape of chromosomes at the time of cell division.

Question 6.
Give six examples of single celled organisms.
Answer:
Paramecium, Amoeba, Chlamydomonas, Euglena, Trypanosoma and Malarial parasite.

Question 7.
Who coined the term ‘Protoplasm’ for the fluid substance of cell?
Answer:
Purkinje (1839).

Question 8.
How it was made possible to observe the complex structures of cell?
Answer:
Discovery of electron microscope.

Question 9.
Name the organelle which takes part in protein synthesis.
Answer:
Ribosomes.

Question 10.
Which is the longest cell in plants.
Answer:
Sclerenchyma.

Question 11.
Name the smallest and largest cells.
Answer:

• Smallest cell – Mycoplasma.
• Largest cell-Ostrich egg.

Question 12.
Name the smallest and largest cell of human body.
Answer:

• Smallest cell – of kidney.
• Largest cell-neuron (nerve cell).

Question 13.
List the factors which denote size of cell.
Answer:

1. Structure
2. Location
3. Function.

Question 14.
What are the two main components of protoplasm?
Answer:
Cytoplasm and nucleoplasm.

Question 15.
Which cell organelle is called suicidal bag?
Answer:
Lysosome.

Question 16.
What is the primary function of lysosome?
Answer:
A centre of intracellular digestion, so is called digestive bag.

Question 17.
Name the cell organelle responsible for protein synthesis.
Answer:
Ribosomes.

Question 18.
Expand DNA.
Answer:
Deoxyribose nucleic acid.

Question 19.
Expand RNA.
Answer:
Ribose nucleic acid.

Question 20.
Who examined thin slice of cork under microscope?
Answer:
Robert Hooke.

Question 21.
What is cork?
Answer:
Cork is obtained from the bark of a tree.

Question 22.
Who coined the term cell?
Answer:
Robert Hooke.

Question 23.
Who examined the living cells for first time?
Answer:
A.V. Leeuwenhoek.

Question 24.
What are unicelluar organisms?
Answer:
The organisms formed of single cell e.g. Amoeba.

Question 25.
What are multicellular organisms?
Answer:
The organisms formed of a large number of cells are termed as multicellular organisms e.g. human beings.

Question 26.
Write examples of multicellular organisms.
Answer:
Fungi, plants and animals.

Question 27.
Write two features of cells of onion peel.
Answer:
Presence of cell wall and large central vacuole.

Question 28.
What is the contribution of Robert Brown in cell biology?
Answer:
Discovered nucleus in the cells of orchid.

Question 29.
What are the two types of cells on the basis of nature of nucleus? *
Answer:
Prokaryotic and Eukaryotic cells.

Question 30.
Name any two prokaryotic cells.
Answer:

• Bacterial cell
• Blue-green algae

Question 31.
Who proposed the cell theory?
Answer:
M.J. Schleiden and Theodore Schwann.

Question 32.
What is cell theory?
Answer:
All plants and animals are made up of cells and cell is the structural and functional unit of life.

Question 33.
Give the contribution of Rudolf Virchow in the field of biology.
Answer:
He stated “omnis cellula e cellula” which means new cells are formed by the growth and division of pre-existing cells.

Question 34.
What is the number of cells present in an adult person?
Answer:
100 trillion (1014).

Question 35.
Which is the smallest measuring unit in the field of cell biology?
Answer:
Angstrom (A).

Question 36.
In which year electron microscope was invented?
Answer:
1940.

Question 37.
What is the nature of plasma membrane?
Answer:
It is formed of lipids and proteins.

Question 38.
Give the primary function of plasma membrane.
Answer:
It regulates exchange of materials between the cytoplasm and extracellular fluid.

Question 39.
Give one term for a semifluid ground substance present between plasma membrane and nucleus.
Answer:
Cytoplasm.

Question 40.
What is diffusion?
Answer:
Diffusion. The movement of substance from a region of higher concentration to a region of lower concentration is called diffusion.

Question 41.
What is the term for movement of water into and out of cell across a semipermeable membrane?
Answer:
Osmosis.

Question 42.
Define plasmolysis.
Answer:
Loss of water from a plant cell resulting in shrinkage or contraction of cell away from cell wall.

Question 43.
Give the common name of the mitochondria.
Answer:
Powerhouses or ATP mills.

Question 44.
Expand ATP.
Answer:
ATP. Adenosine triphosphate

Question 45.
Name two semi-autonomous cell organelles.
Answer:
Mitochondria and plastids.

Question 46.
Which type of enzymes are located inside the mitochondria?
Answer:
Respiratory enzymes.

Question 47.
Name the largest-sized cell organelle.
Answer:
Plastid (chloroplast).

Question 48.
Name three types of plastids.
Answer:
Leucoplasts, chloroplasts and chromoplasts.

Question 49.
Which cell organelle is called kitchen of cell and why?
Answer:
Chloroplast. It is site of photosynthesis in green plants. During this process plant prepare their own food by trapping solar energy and use COz and water as raw materials.

Question 50.
What are chromoplasts?
Answer:
These are coloured plastids with yellow, orange or red coloured plastids.

Question 51.
Write the chemical composition of cell wall.
Answer:
Cellulose.

Question 52.
What is the role of cell wall?
Answer:
Cell wall provide structural support to plant cell.

Question 53.
Which chemical is used to strain plant cell?
Answer:
Iodine, Safranin, methylene blue.

Question 54.
Give one major difference between SER and RER.
Answer:
SER is without ribosomes and is involved in lipid synthesis, while RER is with ribosome-studded cistemae and is involved in protein synthesis.

Question 55.
List two general functions of ER.
Answer:

• ER acts as channels for transport of materials within the cell.
• It also act as cytoskeleton.

Question 56.
Write one function of SER.
Answer:
Detoxification of many poisons and drugs.

Question 57.
Give the primary function of Golgi body.
Answer:
Cell secretion and acts as condensation membrane.

Question 58.
Which plastids are involved in storage of food?
Answer:
Leucoplasts.

Question 59.
What is the main difference between cell organelles and cell inclusions?
Answer:
Cell organelles are living structures of cytoplasm, while cell inclusions are non-living structures of cytoplasm.

Question 60.
Name the vacuolar membrane.
Answer:
Tonoplast.

Question 61.
Why is nucleus called director of cell?
Answer:
It controls and directs all the cellular activities.

Question 62.
Which organelle plays central role in cellular reproduction?
Answer:
Nucleus.

Question 63.
What is nature of nuclear membrane?
Answer:
It is two-layered, lipoproteinaceous, porous and semipermeable.

Question 64.
What is primary function of nuclear membrane?
Answer:
Regulates exchange of materials between nucleoplasm and cytoplasm.

Question 65.
What are the functional units of chromosomes?
Answer:
Genes.

Question 66.
What is the chemical nature of a chromosome?
Answer:
DNA and basic protein histones, so is called Deoxyribonucleoprotein (DNP).

Question 67.
Give the primary function of DNA of chromatin fibre.
Answer:
DNA acts as genetic material and helps in transmission of characters from par¬ents to offsprings.

Question 68.
What is the function of vacuole in plant cell?
Answer:
Vacuoles are full of cell sap and provide rigidity and turgidity to cell vacuoles, temporarily stores wastes.

Question 69.
Write functions of contractile vacuole in plant cell.
Answer:
Osmoregulation and expelling wastes from the cell.

Question 70.
Name the organelle which contains chlorophyll.
Answer:
Chloroplast.

Question 71.
What are two functions of plasma membrane?
Answer:

• Provides shape to cell
• Keeps intact the contents of cell.

Question 72.
What is osmosis?
Answer:
It is a special type of diffusion of solvent molecules from low concentration of solution to higher concentration solution separated by semipermeable membrane.

Punjab State Board PSEB 9th Class Science Important Questions Chapter 4 Structure of the Atom Important Questions and Answers.

PSEB 9th Class Science Important Questions Chapter 4 Structure of the Atom

Long Answer Type Questions:

Question 1.
What is Rutherford’s ∝-ray scattering experiment? Give its observations. How does Rutherford explain this observation?
Answer:
Rutherford’s ∝-ray scattering experiment: In this experiment, Rutherford obtained a thin stream of fast-moving alpha (∝) particles from radioactive source (P₀) and was allowed to strike against a thin foil of heavy metal like gold. Alpha particles are also called helium nuclei (He²⁺ with + 2 unit charge and 4 a.m.u. mass). As a result of the experiment, he made the following observations:

1. Most of the ∝-particles passed through the gold foil without any deflection from their original path.
2. Some of the ∝-particles got deflected by small angles from their original path.
3. A few ∝-particles (approximately 1 out of 10,000) were deflected to a large extent. In some cases, the a-particles came back in the same direction after striking the gold foil.

Explanation for the observations:

We know that the gold foil is made up of atoms of gold which are placed side by side. Since most of the ∝-particles passed through these atoms undeflected they did not come across any obstruction in their path, this shows that most of the space in the atom is light or hollow.

The electrons with negligible mass were supposed to be present in this portion called extra nuclear portion. The a-particies were deflected from their path and a very few came back in the same direction. This shows that they must have met with some obstruction in their path.
The obstruction must be
1. Heavy because a-particles are high speed particles and can remove light obstruction from their path.
2. Small because only a few a-particles got deflected.
3. Positively charged because some a-particles were repelled by this obstruction.

This small, heavy and positively charged portion inside an atom was called nucleus. The protons with mass and positive charge were supposed to be present in the nucleus. Later on, neutrons were also found to be present in the nucleus of the atom.

Question 2.
Discuss in brief Rutherford’s Model of atom.
Answer:
The main points of Rutherford’s model of atom are listed as follows:
1. An atom has two parts. These are nucleus and extra nuclear portion.
2. The nucleus contains protons while electrons are present in the extra nuclear portion.
3. Most of the mass of the atom is due to the nucleus because electrons have negligible mass.

4. The volume occupied by the nucleus is very small as compared to the volume occupied by extra nuclear portion.
5. The electrons in the extra nuclear portion are not stationary. These are revolving around the nucleus. The electrons are called planetary electrons because they can be compared to various planets which revolve around the sun. The nucleus may be compared with the sun.

Question 3.
Discuss the arrangement of the electrons in the different energy levels.
Or
Describe Bohr-Bury scheme for the distribution of electrons in the various orbits or energy levels of an atom.
Answer:
The distribution of electrons in the energy levels is given with the help of Bohr Bury scheme. It is given as follows:
1. The energy levels or energy shells are filled in order of increasing energies. The electrons first enter the K shell (n = 1. which is closest to the nucleus. This is followed by L shell (n = 2), M shell (n = 3) and so on. Here V represents the number of the shell.
2. The maximum number of electrons in any shell is given as 2n² (n = number of the shell). The distribution in the first four energy shells is given in the table given below:
Distribution of electrons in first four energy shells according to 2n² rule.

Symbol of shell	Number of shell (n)	Maximum number of electrons (2n2)
K	1	2 x (1)2 = 2
L	2	2 x (2)2 = 8
M	3	2 x (3)2 = 18
N	4	2 x (4)2 = 32

3. The outermost energy shell cannot have more than 8 electrons. The next inner shell called penultimate shell, cannot have more than 18 electrons.
4. It is not necessary that an energy level or shell is fully filled before the filling in the next energy level starts. In fact, filling of electrons in a new shell starts when any shell contains 8 electrons.
On the basis of the above scheme, let us discus with mass number 24 and atomic number 12.

• Mass no. of atom (A) = 24
• Atomic no. of atom (Z) = 12
• No. of protons in nucleus = 12
• No. of neutrons in nucleus = 12
• No. of electrons to be distributed = 12
• The distribution in the various energy shells: K L M: 2, 8, 2

Question 4.
Give the electronic distribution in the first twenty elements on the basis of Bohr-Bury scheme.
Answer:
On the basis of Bohr-Bury scheme, the distribution of electrons in first twenty elements (Z = 1 to Z = 20) is given below:
Table: Electronic distribution in atoms of first 20 elements

Element (Symbol)	Mass No. (A)	Atomic No. (Z)	No. of Protons (P)	No. of Electrons (e)	No. of Neutrons (n) (A-Z)	Electronic Distribution
						K	L	M	N
1. Hydrogen (H)	1	1	1	1	0	1
2. Helium (He)	4	2	2	2	2	2
3. Lithium (Li)	7	3	3	3	4	9	1
4. Beryllium (Be)	9	4	4	4	5	2	2
5. Boron (B)	11	5	5	5	6	2	3
6. Carbon (C)	12	6	6	6	6	2	4
7. Nitrogen (N)	14	7	7	7	7	2	5
8. Oxygen (O)	16	8	8	8	8	2	6
9. Fluorine (F)	19	9	9	9	10	2	7
10. Neon (Ne)	20	10	10	10	10	2	8
11. Sodium (Na)	23	11	11	11	12	2	8	1
12. Magnesium (Mg)	24	12	12	12	12	9	8	2
13. Aluminium (Al)	27	13	13	13	14 ‘	2	8	3
14. Silicon (Si)	28	14	14	14	14	2	8	4
15. Phosphorus (P)	31	15	15	15	16	2	8	5
16. Sulphur (S)	32	16	16	16	16	2	8	6
17. Chlorine (Cl)	35	17	17	17	18	2	8	7
18. Argon (Ar)	40	18	18	18	22	2	8	8
19. Potassium (K)	39	19	19	19	20	2	8	8	1
20. Calcium (Ca)	40	20	20	20	20	2	8	8	2

Special cases of Potassium and Calcium:

• In case of Potassium (Z = 19), the M shell has only 8 electrons and not 18. Actually, when the M shell gets 8 electrons, the filling of electrons starts in the next shell which is N-shell. When the N-shell gets 2 electrons, the electron are again- filled in the M shell.
• Thus, electronic distribution in potassium (Z = 19) is
  K L M N
  2 8 8 1 (M shell has 8 electrons and N shell has 1 electron)
• Similarly, the electronic distribution in calcium (Z = 20) is:
  K L M N: 2 8 8 2 (M shell has 8 electrons and N shell has 2 electrons)

Question 5.
Define the terms:

1. Atomic number
2. Mass number
3. Atom
4. Ion
5. Element
6. Orbit
7. Nucleons

Answer:

1. Atomic number: It is the number of protons present in the nucleus of an atom of the element.
2. Mass number: It is the sum of number of protons and neutrons present in the nucleus of an atom of the elements.
3. Atom: It is the smallest unit of matter which takes part in chemical reactions and it may or may not exist independently.
4. Ion: It is an atom or group of atoms having charge positive or negative and can exist freely in solution.
5. Element: It is a pure substance which can neither be built up nor broken into two or more still simpler substance by any physical or chemical method and it consists of only one kind of atoms.
6. Orbit: It is the fixed circular path traced by an electron revolving around the
7. Nucleons: The protons and neutrons present in the nucleus of an atom of the element are collectively known as nucleons.u

Short Answer Type Questions:

Question 1.
What do you understand by the structure of atom?
Answer:
According to the Dalton’s atomic theory, the smallest particle of matter is called atom. But later studies have shown that an atom is further made up of sub-atomic particles called electrons, protons and neutrons. Different atoms have different number of such particles and they also differ in the arrangement of these particles. Therefore, the atoms have different properties.

Question 2.
What happens when electric field is applied to the path of cathode rays? What does it show?
Answer:
When electric field is applied to the path of the cathode rays, these are deflected towards the positive plate of the field. This shows that the cathode rays consist of negatively charged particles.

Question 3.
What is the information conveyed by the following observations :

1. Atom is electrically neutral,
2. Mass of the atom is due to the nucleus.

Answer:

1. If an atom is electrically neutral, this means that it will have equal number of protons and electrons. Both protons and electrons have 1 unit charge but with opposite sign.
2. This means that nucleus contains in it both protons and neutrons which have mass.

Question 4.
What is the significance of number of protons found in the atoms in each of the different elements?
Answer:
The number of electrons in atom of the element is equal to the number of protons. By knowing no. of protons, we can calculate no. of electrons and hence its properties.

Question 5.
Write the electronic configuration of the elements A, B, C, D, E with atomic numbers 5, 6, 14, 13 and 15. Which have similar chemical properties?
Answer:

Element	Atomic No. (Z)	Electronic configuration
		K	L	M
A	5	2	3
B	6	2	4
C	14	2	8	4
D	13	?	8	3
E	15	2	8	5

Elements B and C. have similar chemical properties because both of them have 4 valence elt, trons.
Elements A and D have similar chemical properties because both of them have 3 valence electrons.

Question 6.
Five species P, Q, R, S, T have electrons, protons and neutrons are as follows:

Species	Electrons	Protons	Neutrons
P	4	3	4
Q	8	9	9
R	17	17	20
S	17	17	18
T	18	18	22

Find

1. a cation
2. an anion
3. a noble gas and
4. a pair of isotopes.

Answer:

1. Cation – Q
2. Anion – P
3. A noble gas = T
4. Pair of isotopes = R and S (because they have same number of electrons and protons but different number of neutrons).

Question 7.
Helium has only 2 electrons in the K-shell. But it is called an inert gas element. Why?
Answer:
Helium (He) atom has only one shell (K-shell) which can have a maximum of 2 electrons only. It cannot have more than 2 electrons. As a result, the combining capacity of He is zero. Therefore, its valency is also zero.

Question 8.
Give labelled diagram to show how are cathode rays produced?
Answer:

Question 9.
An atom has mass number A and atomic number Z.
1. How many protons are present in the nucleus?
2. How many electrons are revolving around the nucleus?
3. How many neutrons are present in its nucleus?
Answer:
Mass number = A
Atomic number = Z
1. No. of protons present in the nucleus = Z
2. No. of electrons revolving around the nucleus = Z
3. No. of neutrons present in the nucleus = A – Z.

Question 10.
State three ways by which a proton differs from an electron.
Answer:

Proton	Electron
1. It has one unit of positive charge. 2. It has mass 1.6 x 10-24 g. 3. It is present in the nucleus of an atom.	It has one unit of negative charge. It has mass 9.1 x 10″28 g. It is present in the extranuclear part of an atom.

Question 11.
What are isotopes? Give two uses of isotopes. Name the isotopes of hydrogen. Give their structures.
Answer:
Isotopes. The atoms of the same element having the same atomic number but different mass numbers are called isotopes.
Use of isotopes:
1. Isotopes of hydrogen, oxygen, carbon are used to study the mechanisms of organic reactions.
2. Some radioactive isotopes are used for the treatment of cancer and other diseases. The isotopes of hydrogen are:

Question 12.
Explain why elements have fractional atomic masses?
Answer:
The elements have fractional atomic masses due to the existence of isotopes (having different mass numbers) e.g. chlorine has two isotopes \({ }_{17}^{35} \mathrm{Cl}\) and \({ }_{17}^{37} \mathrm{Cl}\) and are present in the ratio 3:1.
∴ Average atomic mass of chlorine = \(\frac{35 \times 3+37 \times 1}{4}=\frac{105+37}{4} \) = 35.5 a.m.u.

Question 13.
What are isobars? Give examples.
Answer:
The atom of different elements having same mass numbers but different atomic numbers are called isobars.
e.g. 1. \({ }_{18}^{40} \mathrm{Ar}\) and \({ }_{19}^{40} \mathrm{Ar}\)
2. \({ }_{36}^{86} \mathrm{Ar}\) and \({ }_{38}^{86} \mathrm{Ar}\)

Question 14.
Sulphur has an atomic number 16 and a mass of 32. State the number of protons and neutrons in the nucleus of sulphur. Give a simple diagram to show the arrangement of electrons in an atom of sulphur.
Answer:

Atomic number of S = 16
Mass number of S = 32
∴ No. of protons = 16
No. of neutrons = 32 – 16 = 16
No. of electrons = 16

Question 15.
Write down the electronic configuration of the following:
1. \({ }_{13}^{27} \mathrm{X}\)
2. \({ }_{17}^{35} \mathrm{X}\)
Write down the number of electrons in X and neutrons in Y and the formula of
compound formed by X and Y.
Answer:
1. \({ }_{13}^{27} \mathrm{X}\)
Atomic number of X = 13
Mass number of X =27
No. of protons in X = 13
∴ No. of electrons in X = 13
The electronic configuration of X = 2, 8, 3
Valency of X = 3

2. \({ }_{17}^{35} \mathrm{X}\)
Atomic number of Y = 17
Mass number of Y =35
No. of protons in Y = 17
No. of electrons in Y = 17
No. of neutrons in Y = 35 – 17 = 18
The electronic co0nfiguration of Y = 2, 8, 7
Valency of Y = 1
The formula of the compound formed by X and Y

Question 16.
Give the important properties or characteristics of isotopes.
Answer:

1. The isotopes of an element have same atomic number (Z) i.e. the same number of electrons and same number of protons. Hence, they have identical chemical properties.
2. Isotopes of an element have same number of valence electrons and hence same valency.
3. Isotopes of an element have different mass numbers (or different number of neutrons) and hence they have different physical properties such as mass, density, melting point, boiling point etc.

Question 17.
An atom of the element is represented as 11x?

1. What does the numeral 23 indicate?
2. What does the nemeral 11 indicate?
3. What is the number of protons in X?

Answer:

1. 23 indicates mass number of X.
2. 11 indicates atomic number of X.
3. No. of protons in X = Atomic number = 11.

Question 18.
The atom of an element is made up of 4 protons, 5 neutrons and 4 electrons. what are its atomic number and mass number?
Answer:
No. of proton = 4
Atomic number of the element, Z = 4
No. of neutrons = 5
∴ No. of protons + No. of neutrons =4 + 5 = 9
∴ Mass number of the element, A = 9.

Question 19.
Calculate the number of neutrons in the following elements:
1. \({ }_{1}^{3} \mathrm{Cl}\)
2. \({ }_{17}^{37} \mathrm{Cl}\)
3. \({ }_{20}^{40} \mathrm{Cl}\)
Answer:
1. \({ }_{1}^{3} \mathrm{Cl}\)
Mass number = 3
Atomic number = 1
No.of neutrons = Mass no – Atomic no.
= 3 – 1 = 2

2. \({ }_{17}^{37} \mathrm{Cl}\)
Mass number = 37
Atomic number = 17
No.of neutrons = 37 – 17 = 20

3. \({ }_{20}^{40} \mathrm{Cl}\)
Mass number = 40
Atomic number = 20
No.of neutrons = 40 – 20 = 20

Question 20.
Give two conditions under which cathode rays are produced.
Answer:
Cathode rays are produced when a gas is subjected to the action of
1. High voltage of the order of 5000-10000 V and
2. Under a low pressure of the order of 10^-3 atm of Hg.

Question 21.
The electronic configuration of P (Z = 15) is 2, 8, 5. Why is the valency of phosphorus 3 and not 5?
Answer:
The electronic configuration of phosphorus (P) shows that it has 5 valence electrons. Its valency is expected to be 5. But it is not possible for the atom to lose 5 electrons present in the valence shell because the energy required to remove these electrons will be very high. Therefore, phosphorus atom has valency equal to 3 because to gain 3 electrons is easier than losing 5 electrons as it requires less energy.

Question 22.
What information is conveyed by the statement that the mass number of magnesium is 24 and the atomic number is 12?
Answer:
The atomic number (12) of magnesium indicates that its atom has 12 protons in the nucleus and an equal number of electrons in the extra nuclear portion. The mass number (24) points out that there are also 12 neutrons (24 – 12 = 12) present in the nucleus alongwith protons.

Question 23.
Is it possible for an atom to have 12 protons and 13 electrons? Explain.
Answer:
No, it is not possible. An atom must always be electrically neutral. This means that it has no net charge present on it. Now, each proton has one unit positive charge and each electron has one unit negative charge. In a neutral atom, the number of electrons and protons must always be the same. Thus, an atom cannot have 12 protons and 13 electrons.

Question 24.
Give the important isotopes of hydrogen, carbon, oxygen and chlorine. Indicate their mass numbers and atomic numbers.
Answer:

Numerical Problems (Solved):

Question 1.
Chlorine has two isotopes \({ }_{17}^{35} \mathrm{Cl}\) and \({ }_{17}^{37} \mathrm{Cl}\) in the ratio 3 : 1. Calculate the average atomic mass of chlorine.
Solution:

Question 2.
Out of ₁₈X and ₁₆Y which atom is chemically more reactive?
Solution:

No. of valence electrons in X =8
No. of valence electrons in Y =6
∴ Y is more reactive.

Question 3.
An element has 12 neutrons and mass number 23. Give the atomic number and symbol of the element.
Solution:

• Mass number(A) = 23
• Number of neutrons = 12
• Number of protons = 23 – 12 = 11
• Atomic Number(Z)= 11
• Symbol of the element = \(\frac{23}{11} \mathrm{Na}\)

Question 4.
Calculate number of protons, neutrons and electrons in \(\frac{235}{92} \mathrm{U}\) and \(\frac{238}{92} \mathrm{U}\). How are these atoms related?
Solution:
table
\(\frac{235}{92} \mathrm{U}\) and \(\frac{238}{92} \mathrm{U}\) are isotopes.

Question 5.
Calculate the number of electrons, protons and neutrons is \(\frac{19}{9} \mathrm{U}\). Also calculate its valency.
Solution:

1. Atomic number = 9
2. Mass number = 19
3. No. of protons = 9
4. No. of neutrons = 19 – 9 = 10
5. Electronic configuration = 2 7
6. Valency = 8 – 7 = 1.

Very Short Answer Type Questions

Question 1.
Who discovered canal rays?
Answer:
Goldstein discovered canal rays in 1886.

Question 2.
Which charge is present on canal ray particles?
Answer:
They carry positive charge.

Question 3.
Which charge is present on protons?
Answer:
Positive charge.

Question 4.
Where are protons present in an atom?
Answer:
Protons are present in the nucleus, deep inside the atom.

Question 5.
What were the characteristics of an atom according to Dalton?
Answer:
According to Dalton an atom was indivisible and indestructible.

Question 6.
Which discovery is against Dalton’s theory?
Answer:
Discovering of electrons and protons in an atom.

Question 7.
Who proposed the first model for the structure of atom?
Answer:
J.J. Thomson.

Question 8.
Why did Rutherford used gold foil in a-ray scattering experiment?
Answer:
This is because he wanted as thin a layer as possible. It was about 1000 atoms thick.

Question 9.
What are α-particles?
Answer:
They are doubly charged helium ions (He²⁺).

Question 10.
What is the charge on α-particles?
Answer:
+2 units.

Question 11.
What is the mass of an α-particle?
Answer:
4 u.

Question 12.
How the defects of Rutherford’s model were removed by Neil Bohr?
Answer:
The electrons revolve around the nucleus in an atom in fixed circular paths called orbits or energy levels and don’t lose energy.

Question 13.
What are energy levels or shells?
Answer:
The definite orbits in where electrons revolve around the nucleus are called energy levels. These are designated as K, L, M, N ……………. 1, 2, 3, 4.

Question 14.
Define mass number of an element.
Answer:
It is the sum of number of neutrons and protons present in the nucleus of the atom of the element.

Question 15.
Who gave the distribution of electrons in the various shells of an atom?
Answer:
Bohr and Bury.

Question 16.
What is the maximum number of electrons present in an electronic shell?
Answer:
2n² (Where n is the number of shells).

Question 17.
What is the maximum first four shells of an atom?
Answer:
2, 8, 18, 32.

Question 18.
What is the maximum number of electrons in the outermost shell of an atom?
Answer:
8

Question 19.
Which elements are chemically inert?
Answer:
These are the elements which have 8 electrons in their outermost shells.

Question 20.
Define octet.
Answer:
The maximum number of electrons present in the outermost shell of an atom is called octet.

Question 21.
Define valency of an element.
Answer:
It is the combining capacity of an atom of the element and it is equal to the number of electrons lost or gained or contributed for sharing from its valence shell in order to complete its octet.

Question 22.
Define atomic number.
Answer:
It-is the number of protons present in the nucleus of an atom of the element.

Question 23.
Define nucleon.
Answer:
The neutrons and protons present in the nucleus of an atom of the element are collectively known as nucleons.

Question 24.
Where is most of the mass of the element present?
Answer:
In the nucleus of an atom.

Question 25.
Define atomic mass of an element.
Answer:
It is the sum of the number of neutrons and protons present in the nucleus of its atom.

Question 26.
What are isotopes?
Answer:
Atoms of the same element having same atomic number but different mass numbers are called isotopes.

Question 27.
Write two isotopes of chlorine.
Answer:
\({ }_{17}^{35} \mathrm{Cl}\) and \({ }_{17}^{37} \mathrm{Cl}\).

Question 28.
Write two isotopes of carbon.
Answer:
\({ }_{6}^{12} \mathrm{Cl}\) and \({ }_{6}^{14} \mathrm{Cl}\).

Question 29.
Isotope of which element is used in the treatment of cancer?
Answer:
Isotope of cobalt (\({ }_{27}^{59} \mathrm{Co}\)).

Question 30.
What is the atomic mass of chlorine?
Answer:
35.5

Question 31.
Isotope of which element is used for the treatment of goitre?
Answer:
An isotope of iodine.

Question 32.
Isotope of which element is used in atomic reactor?
Answer:
Uranium.

Question 33.
What are isobars?
Answer:
Atoms of the different elements having same mass number but different atomic numbers are called isobars.

Question 34.
Give one example of isobars?
Answer:
\(\underset{(\text { Calcium })}{\stackrel{40}{20} \mathrm{Ca}}\) and \(\underset{(\text { Argon })}{\stackrel{40}{18} \mathrm{Ca}}\).

Question 35.
Write three isotopes of hydrogen.
Answer:

1. Protium (\({ }_{1}^{1} \mathrm{H}\))
2. Deuterium (\({ }_{2}^{1} \mathrm{H}\))
3. Tritium (\({ }_{3}^{1} \mathrm{H}\)).

Question 36.
What is the total number of electrons in an atom if its K-and L-shells are fully filled?
Answer:
10 (K-2, L-8).

Question 37.
What electrons in an atom influence its chemical properties?
Answer:
Valence electrons (electrons in the outermost shell).

Question 38.
How will you represent chlorine atom having mass number 35 and atomic number 17?
Answer:
\({ }_{17}^{35} \mathrm{Cl}\)

Question 39.
Name the sub-atomic particle on which size of an atom depends?
Answer:
Electron.

Question 40.
Name the atoms having same atomic number but different mass numbers.
Answer:
Isotopes.

Question 41.
Mg²⁺ has 10 electrons, what is the number of protons in it?
Answer:
10 + 2 = 12.

Question 42.
Name the element which has no neutrons in the nucleus of its atom.
Answer:
Hydrogen.

Question 43.
Out of electrons, protons and neutrons, which are same in isotopes?
Answer:
Electrons and protons.

Question 44.
There are three isotopes of hydrogen, \({ }_{1}^{1} \mathrm{H},{ }_{1}^{2} \mathrm{H},{ }_{1}^{3} \mathrm{H}\) all are electrically neutral, why?
Answer:
This is because each isotope has one electron and one proton.

Question 45.
An element has atomic number 16. Give its electronic configuration and number of valence electrons.
Answer:
Electronic configuration 2, 8, 6.

Question 46.
The number of electrons in the valence shell of sodium (Na) is ……………… .
Answer:
1.

Question 47.
Fluorine belongs to …………… family.
Answer:
Halogen.

Question 48.
In an atom, the number of …………… is the same as the number of ………………. .
Answer:
Electrons, protons

Question 49.
Sodium has …………….. electron …………….. than sodium ion.
Answer:
One, more

Question 50.
Isotopes of an element are …………….. because they have ……….. number of electrons.
Answer:
Chemically similar, same

Question 51.
The number of electrons in the valence shell of an atom cannot be ………………..>
Answer:
More than eight.

Punjab State Board PSEB 9th Class Science Important Questions Chapter 3 Atoms and Molecules Important Questions and Answers.

PSEB 9th Class Science Important Questions Chapter 3 Atoms and Molecules

Long Answer Type Questions:

Question 1.
(a) Write the important postulates of the Dalton’s Atomic Theory.
(b) Give four drawbacks of Dalton’s Atomic Theory.
Answer:
(a) Dalton’s atomic theory was given by John Dalton in 1808 to e×plain the nature of an atom and the chemical combination in the atoms. The main points of the theory are:

1. All matter is made up of a large number of e×tremely small particles called atoms.
2. An atom cannot be further divided.
3. Atoms are of different kinds. There are as many kinds of atoms as are of elements.
4. Atoms of a particular element are identical in all respects i.e. they have same mass and similar properties.
5. Atoms of the different elements are different i.e. they have different masses and properties.
6. Two or more atoms of the same or different elements combine to form compound atoms or molecules of compounds.
7. The number and the nature of atoms in a molecule always remains the same.
8. Atoms of the different elements combine in a simple whole number but fi×ed ratios to form compound atoms (now called molecules).
9. Atoms of the same element can combine to form two or more compounds.
10. Atom can neither be created nor be destroyed.

(b) Drawbacks of Dalton’s Atomic Theory:

1. Atom is no longer indivisible.
2. Atoms of the same element may not be always identical.
3. Atoms of different elements may have same atomic masses.
4. It does not e×plain the cause of chemical combination.

Question 2.
How to write a chemical formula of an ionic compound from its radicals?
Answer:
While writing the formula of an ionic compound, the following steps are used :

1. Write down the symbol or formula of positive ion to the left and the symbol or formula of the negative ion to the right.
2. Shift the valency of positive ion to the lower right of the negative ion and the valency of negative ion to the lower right of the positive ion.
3. Take out the common factor if any.
4. The formula compound radical is enclosed in small brackets and subscript is put outside the bracket. The subscript 1 is omitted.

Example

Question 3.
How will you write the name of a binary molecular compound?
Answer:
A covalent compound made up of two elements is called a binary molecular compound, e.g. water (H₂0).
While writing the name of a binary molecular compound, first write the name of the element whose symbol appears on the left hand side in the molecular formula and write down the name of other element. The name of the other element should end with ‘ide’. The prefi×es di, tri, tetra, penta etc. are used to indicate 2, 3, 4, 5…. atoms of an element.

Some examples are:

• Compound – Name
• CO – Carbon mono×ide
• CO₂ – Carbon dio×ide
• ZnO – Zinc O×ide
• SO₂ – Sulphur dio×ide
• PCl₃ – Phosphorus trichloride
• PCl₅ – Phosphorus pentachloride

Question 4.
Give one experiment to prove the truth of law of conservation of mass.
Answer:
1. Prepare 5% solution of barium chloride and sodium sulphate in separate beaker.
2. Take a small amount of solution of barium chloride in a conical flask and a small amount of solution of sodium sulphate in an ignition tube.

3. Suspend the ignition tube carefully in the conical flask with a thread and cork it.
4. Weigh the flask carefully. To prove the law of conservation of mass
5. Tilt and swirl the flask such that the two solutions get mi×ed and react.
6. Cool the flask to room temperature and again weigh it. The weight remains unchanged showing the truth of the law.

Short Answer Type Questions

Question 1.
Differentiate between an atom and a molecule.
Answer:

Atom	Molecule
1. It is the smallest particle of an element which takes part in chemical reactions. It may or may not exist freely.	1. It is the smallest particle of a substance which can exist freely.
2. Generally it is highly reactive.	2. It is less reactive.
3. It is less stable.	3. It is more stable.
4. It can’t be sub-divided.	4. It can be sub-divided.

Question 2.
(a) What do you understand by the term chemical formula?
(b) What qualitative information is given by the formula NH₃?
Answer:
(a) Chemical formula. The symbolic representation of a molecule of a substance is called its chemical formula. It indicates the actual number of atoms of various elements present in one molecule of a substance.
(b) NH₃ represents ammonia.

Question 3.
Write down the formulae of:
(a) Aluminium oxide
(b) Aluminium chloride
(c) Hydrogen sulphide
Answer:

Question 4.
Calculate the relative molecular masses of:
(a) Water (H₂O)
(b) Nitric Acid (HNO₃).
Answer:
(a) Molecular mass of water (H₂O) = 2 × 1 + 16 = 2 +16 = 18u.
(b) Molecular mass of nitric acid (HNO₃) = 1 + 14 + 3 × 16 =1 + 14 + 48 = 63u.

Question 5.
Write down the names of the compounds represented by the following formulae:

1. Na₂CO₃
2. MgCl₂
3. Al₂ (SO₄)₂
4. K₂ S0₄
5. NiS0₄
6. KN0₃
7. CaC0₃

Answer:

1. Sodium Carbonate
2. Magnesium Chloride
3. Aluminium Sulphate
4. Potassium Sulphate
5. Nickel Sulphate
6. Potassium Nitrate
7. Calcium Carbonate.

Question 6.
Work out the formula of:
1. Ammonia
2. Carbon dio×ide
3. Carbon tetrachloride.
Answer:

Question 7.
Calculate the number of moles in:
1. 52 g of He
2. 12.044 × 10₂₃ atoms of He
Answer:

Question 8.
Give one e×ample in each case;
(a) Diatomic molecule
(b) Triatomic molecule
(c) Monoatomic molecule
Answer:
(a) Dihydrogen (H₂)
(b) Ozone (0₃)
(c) Helium (He).

Question 9.
An element A has a charge of 3+. Write down the formulae of its:
(a) Chloride
(b) Sulphate
(c) Nitrate and
(d) Phosphate
Answer:

Question 10.
Write the formulae and names of the compounds between:
1. Sodium and sulphate ions
2. Aluminium and chloride ions
Answer:

Question 11.
Write the formulae of the compounds formed by:

1. Cr³⁺ and F^–
2. Pb²⁺ and \(\mathrm{SO}_{4}^{2-}\)
3. Mg²⁺ and S^2-
4. \(\mathrm{NH}_{4}^{+}\) and \(\mathrm{Cr₂O}_{7}^{2-}\)
5. K⁺ and \(\mathrm{CrO}_{4}^{2-}\)

Answer:

Question 12.
Calculate the formula mass of Na₂CO₃.10H₂O.
Answer:
Formula mass of Na₂,CO₃.10H₂O = 2 × 23 + 12 + 3 × 16 + 10 (2 × 1 + 16)
= 46 + 12 + 48 + 10 (2 + 16)
= 46 + 12 + 48 + 180
= 286 a.m.u.

Question 13.
(a) What do you understand by trivial names of compounds?
(b) Give the chemical names of five such compounds and give their trivial names.
Answer:
(a) The names of the compounds which do not follow any systematic rules are called trivial names or common names.
(b)

Compound	Chemical name	Trivial name
NH3	Nitrogen trihydride (AZANE)	Ammonia
NaCl	Sodium chloride	Common salt or Table salt
H2O	Hydrogen hydroxide (OXIDANE)	Water
NaOH	Sodium hydroxide	Caustic soda
PH3	Phosphorous trihydride (PHOSPHANE) .	Phosphine.

Question 14.
Calculate:
1. The number of atoms in 46 g of Na
2. No. of molecules in 8 g of O₂
Answer:

Question 15.
An element × shows two valencies i.e. 2 and 4. Write the formulae of its o×ides.
Answer:

∴ Formula of oxide – xO

Question 16.
Write the formulae of the following salts:

• Zinc carbonate
• Ammonium sulphate
• Barium chloride
• Sodium nitrate
• Lead hydro×ide
• Potassium permanganate

Answer:

• Name of the compound – Formula
• Zinc carbonate – ZnCO₃
• Ammonium sulphate – (NH₄)₂SO₄
• Barium chloride – BaCl₂
• Sodium nitrate – NaN0₃
• Lead hydro×ide – Pb(OH)₂
• Potassium permangante – KMnO₄

Question 17.
Write the names of the following compounds:

1. Al₂(S0₄)₃
2. Mg(HCO₃)₂
3. (NH₄)₂S
4. KMnO₄
5. KClO₃

Answer:
Formula of the Compound Name

1. Al₂(S0₄)₃ – Aluminium sulphate
2. Mg(HC0₃)₂ – Magnesium bicarbonate
3. (NH₄)₂ S – Ammonium sulphide
4. KMnO₄ – Potassium permanganate
5. KClO₃ – Potassium chlorate

Numerical Problems (Solved)

Question 1.
Weight of copper o×ide obtained by treating 2.16 g metallic copper with nitric acid and subsequent ignition was 2.70 g. In another e×periment, 1.15 g of copper o×ide on reduction yielded 0.92 g of copper. Show that these results illustrate the law of definite proportions.
Solution:
First experiment

• Weight of copper = 2.16 g
• Weight of copper o×ide = 2.70 g
• Percentage of copper in copper o×ide = \(\frac{2.16}{2.70}\) × 100 = 80
• Percentage of o×ygen in copper o×ide = 100

Second Experiment

• Weight of copper o×ide = 1.15 g
• Weight of copper = 0.92 g
• Percentage of copper in copper o×ide = \(\frac{0.92}{1.15}\) × 100 = 80
• Percentage of O in CuO = 100 – 80 = 20
• Since the percentage composition of copper o×ide in the two e×periments is the same. The above results illustrate the law of definite proportions.

Question 2.
Carbon and oxygen combine in the ratio 3 : 8 by mass to form carbon dio×ide. What mass of o×ygen would be required to react completely with 6 g of carbon?
Solution:
3 g of carbon gas reacts with o×ygen = 8 g
∴ 6g of carbon gas will react with o×ygen = 8/3 × 6 = 16 g

Question 3.
In water molecule the ratio by mass in which hydrogen and o×ygen react is 1 : 8. Calculate the ratio by number of atoms in water molecules.
Solution:

Element	Ratio by mass	Atomic mass	Relative no. of atoms	Simplest Atomic ratio
H	1	1	1/1 = 1	2
O	8	16	8/16 = 1/2 = 0.5	1

∴ Ratio by atoms in water molecule is H : O
2 : 1

Question 4.
Calculate the formula masses of the compounds whose formulae are given below:

1. MgO
2. CaCl₂
3. CaC0₃

Solution:
Formula mass of

1. MgO – 24 + 16 – 40 amu
2. CaCl₂ = 40 + 2 × 35.5 = 40 + 71 = 111 amu
3. CaC0₃ = 40 + 12 + 3 × 16 – 100 amu

Question 5.
What is the weight of 01 mole of HCl?
Solution:
Molecular weight of HCl = 1 + 35.5 = 36.5
Therefore, according to the mole-concept,
Weight of 1 mole of HCl = 36.5 g
∴ Weight of 0.1 mole of HCl = 36.5 × 01 g = 3.65 g

Question 6.
How many g of H₂O are present in 0.2 mole of it?
Solution:
Molecular weight of H₂O = 2 × 1 + 16 = 18
Therefore according to the mole-concept,
Number of grams present in 1 mole of H₂O = 18
∴ Number of grams present in 0-2 mole of H₂O = 0.2 × 18 = 3.6.

Question 7.
What is the mass of 0.1 mole of CO₂ in g?
Solution:
Molecular weight of CO₂ = 12 + 2 × 16 = 44
Therefore according to the mole concept
Mass of 1 mole of CO₂ = 44 g
∴ Mass of 0.1 mole of CO₂ = 44 × 0.1 g = 4.4 g

Question 8.
Calculate the number of moles of phosphorus atoms (P) in 100 g of phosphorus (Atomic mass of P = 31).
Solution:
The gram atomic mass of phosphorus (P) = 31 g
31 g of phosphorus atoms = 1 mole
100 g of phosphorus atoms = 100/31 =3.2 moles.

Question 9.
How many grams of o×ygen gas contain the same number of molecules as are present in 16 grams of sulphur dioxide? (Atomic masses : S = 32, O = 16).
Solution:
Gram molecular mass of sulphur dio×ide (S0₂) = 32 + 2 × 16 = 64 g
64 g of S0₂ contains = 6.022 × 10₂₃molecules
∴ 16 g of S0₂ contains = \(\frac{6.022 × 10₂₃}{64}\) × 16 = 1.5 × 10₂₃ molecules
Gram molecular mass of o×ygen (O₂) = 32 g
Gram Molecular mass of O₂ contain = 6.022 × 10₂₃molecules
Now 6.022 × 10₂₃ molecules of O₂ = 32 g
∴ 1.5 × 10₂₃ molecules of O₂ = \(\frac{32 × 1.5 × 10₂₃}{6.022 × 10₂₃}\) = 7.97 g

Question 10.
What is the mass in grams of each of the following:
(a) 1.0 mole of Ag
(b) 0.5 mole of Mg
(c) 6.023 × 10₂₃ atoms of P?
(Atomic mass : Ag = 108, Mg = 24, P = 31).
Solution:
(a) Atomic mass of Ag = 108
Gram atomic mass of Ag = 108 g
Gram atomic mass of Ag is the mass of 1.0 mole of Ag atoms.
∴ Mass of 1.0 mole of Ag atoms in grams = 108 g

(b) Atomic mass of Mg = 24
Gram atomic mass of Mg = 24 g
Gram atomic mass of Mg is the mass of 1.0 mole of Mg atoms
∴ Mass of 1 mole of Mg atoms in grams = 24 g
Mass of 0.5 mole of Mg atoms in grams = 24 × 0.5 = 12 g

(c) Atomic mass of P = 31
Gram atomic mass of P = 31 g
Gram atomic mass of P contains 6.023 × 10₂₃ atoms of P
6.023 × 10₂₃ atoms of P weigh = 31 g.

Question 11.
Calculate the number of o×ygen atoms in 010 mole of Na₂CO₃ . 10H₂O.
Solution:
Number of oxygen atoms in one molecule of Na₂CO₃.10H₂O
= 3 + 10 = 13
∴ Number of oxygen atoms in 1 mole of Na₂CO₃.10H₂O
= 13 moles
= 12 × 6.022 × 10²³
= 78.286 × 10²³
= 7.8 × 10²⁴

Question 12.
Calculate the actual weight of:
(a) an atom of oxygen
(b) a molecule of NH₃.
Solution:
(a) Atomic weight of oxygen = 16
∴ 1 gram atom of oxygen = 16 g
According to the mole concept,
Number of atoms in 16 g of oxygen = 6.023 × 10²³
i.e. Actual weight of 6.022 × 10²³ atoms of oxygen = 16 g
∴ Actual weight of 1 atom of oxygen = \(\frac{16}{6.022 × 10²³}\) g
= 2.651 × 10²³ g

(b) Molecular weight of ammonia (NH₃) = 14 + 3 × 1 = 17
∴ 1 mole of ammonia = 17 g

Question 13.
Find the number of molecules in 1.8 g of H₂O.
Solution:
Molecular weight of H₂O = 2 × 1 + 16 = 18
∴ According to mole-concept,
Number of molecules in 18 g of H₂O = 6.022 × 10₂₃
= 6.022 × 10²³
∴ Number of molecules in 1.8 g of H₂O =
\(\frac{6.022 × 10²³}{18}\) × 18
= 6.022 × 10²²

Question 14.
Which of the following would weigh most?
(a) 1 Mole of H₂O
(b) 1 Mole of CO₂
(c) 1 Mole of NH₃
(d) 1 Mole of CO
Answer:
1 Mole of H₂O = (2 × 1 + 16) g = 18 g
1 Mole of CO₂ = (12 + 2 × 16) g = 44 g
1 Mole of NH₃ = (14 + 3 × 1) g = 17 g
1 Mole of CO = (12 + 16) g = 28 g
∴ 1 Mole of CO₂ weighs most.

Question 15.
Calculate the number of moles of phosphorus atoms in 100 g of phosphorus. If phosphorus is considered to contain P4 molecules, then how many moles it has?
Solution:
Atomic mass of phosphorus = 31
∴ According to mole-concept,
Number of moles of phosphorus in 31 g = 1
Number of moles of phosphorus in 100g = 1/31 × 100 = 3.22
If phosphorus is considered to contain P₄ molecules, then according to mole-concept, Number of moles in 4 × 31 i.e. 124 g = 1
∴ Number of moles in 100 g = 1/124 × 100 = 0.805

Question 16.
Find the number of hydrogen atoms in 0.1 mole of H₂SO₄.
Solution:
Number of hydrogen atoms in 1 mole of H₂SO₄ = 2 × 6.022 × 10₂₃
Number of hydrogen atoms in 0-1 mole of H₂SO₄ = 0.1 × 2 × 6.022 × 10₂₃
= 1.2044 × 10₂₃ = 1.2 × 10₂₃

Question 17.
Calculate the number of atoms in each of the following:
(a) 52 moles of He
(b) 52 amu of He
(c) 52 g of He
Solution:

Very Short Answer Type Questions:

Question 1.
When did Indian philosophers thought of division of matter?
Answer:
Around 500 B.C.

Question 2.
What was the view of Maharishi Kanad regarding the division of matter?
Answer:
The smallest particle of matter will be indivisible.

Question 3.
What was the name of smallest indivisible particle by Kanad?
Answer:
Atom.

Question 4.
Which two Greek philosophers considered smallest particle as indivisible?
Answer:
Democritus and Leucippus.

Question 5.
What is the ratio by mass of H and O in water?
Answer:
1 : 8.

Question 6.
What is the ratio by mass of N and H in NH3?
Answer:
14 : 3,

Question 7.
What is Prout’s law of constant composition?
Answer:
A pure chemical compound is always made up of same elements combined together in the same fixed ratio by mass.

Question 8.
Who gave Atomic theory?
Answer:
John Dalton.

Question 9.
When did John Dalton gave atomic theory?
Answer:
In 1808.

Question 10.
What are the units used to e×press the atomic radius?
Answer:
Nanometre (nm).

Question 11.
What is the relationship between m and nm?
Answer:
1 nm = 10-9m.

Question 12.
What is the building block of all matter?
Answer:
Atom.

Question 13.
Who was the first scientist which used symbols for elements?
Answer:
Dalton.

Question 14.
What was special about symbols of elements given by Berzelius?
Answer:
The symbols of elements were represented by one or two letters of the name of the element.

Question 15.
What were the units used for e×pressing atomic masses of elements initially?
Answer:
Initially 1 /16th of mass of an atom of naturally occuring oxygen (016-isotope) was taken as unit.

Question 16.
When was C¹² isotope universally accepted as standard reference for expressed atomic masses?
Answer:
In 1961.

Question 17.
Which unit is used now-a-days to e×press atomic masses?
Answer:
It is 1 /12th of mass of an atom of carbon (C¹² – isotope).

Question 18.
Name the smallest particle of an element or compound which can exist freely?
Answer:
Molecule.

Question 19.
What is obtained when the atoms of the same element combine?
Answer:
Molecule.

Question 20.
How many atoms are present in oxygen molecule.
Answer:
Two, hence, it is called diatomic molecule (O₂).

Question 21.
Give four examples of diatomic molecules.
Answer:
H₂, O₂, N₂ and Cl₂.

Question 22.
Give one example of tetra-atomic molecule.
Answer:
Phosphorous, (P₄).

Question 23.
Give one example sample of octa-atomic molecule.
Answer:
Sulphur, (S₈).

Question 24.
What is produced when three atoms of oxygen combine.
Answer:
Ozone (O₃).

Question 25.
Name isotopes of carbon.
Answer:
C¹², C¹³ and C^14.

Question 26.
What is the ratio by mass of C and O in carbon dioxide?
Answer:
3 : 8

Question 27.
What is the ratio by number between the atoms of H and O in water?
Answer:
2 : 1

Question 28.
Define an ion.
Answer:
It is an atom or group of atoms having charge (positive or negative).

Question 29.
What is a cation?
Answer:
It is an ion having positive charge.

Question 30.
What is an anion?
Answer:
It is an ion having negative charge.

Question 31.
What is the ratio by mass of Ca nd O in calcium oxide (CaO)?
Answer:
5 : 2

Question 32.
What is the ratio by mass of Mg and S in magnesium sulphate?
Answer:
3 : 4

Question 33.
What is the ratio by mass of Na and Cl in sodium chloride (NaCl)?
Answer:
23 : 35.5

Question 34.
Define chemical formula?
Answer:
It is the symbolic representation of a molecule of a substance.

Question 35.
Define valency.
Answer:
It is the combining capacity of an atom of the element.

Question 36.
What are diatomic molecules?
Answer:
These are made up of two atoms made up of same or different elements.

Question 37.
Define molecular mass of a subtance?
Answer:
It is the average relative mass of one molecule of substance as compared to the mass of one atom of carbon, (C¹²-isotope).

Question 38.
Which unit is used for expressing molecular masses?
Answer:
a.m.u.

Question 39.
What is the new name given to a.m.u. by IUPAC?
Answer:
U (Unified).

Question 40.
Name the elements present in water (H₂O).
Answer:
Hydrogen and oxygen.

Question 41.
What is one mole of an element?
Answer:
It is the number of an element whose mass in grams is numerically equal to its atomic mass e×pressed in a.m.u. or 1 gram atom of an element represents one mole.

Question 42.
What is Avogardro’s number?
Answer:
Avogardro’s number contains 6.022 × 10²³ particles.

Question 43.
How is Avogadro’s number denoted?
Answer:
By No or NA.

Question 44.
In what ratio elements combine to form a compound?
Answer:
In a fixed ratio by mass.

Question 45.
Which scientist gave law of conservation of mass?
Answer:
Russian scientist Lavoisier in 1756.

Question 46.
Which scientist gave law of constant composition?
Answer:
French scientist Joseph L. Proust in 1799.

Question 47.
What does a.m.u. represent?
Answer:
It is the unit used to express atomic masses.

Question 48.
Which isotope of carbon is used as a standard reference to express atomic masses?
Answer:
C¹² – isotope.

Question 49.
Most of the elements have fractional atomic masses, what does it show?
Answer:
This indicates the existence of isotopes of an element.

Question 50.
What is molar mass?
Answer:
It is the mass of 1 mole of a substance in grams.

Question 51.
Define gram atomic mass.
Answer:
It is the mass of 1 mole of atoms (6.022 × 10²³) in grams.

Question 52.
How many atoms are present in 1 gram atom of an element?
Answer:
6.022 × 10²³.

Question 53.
Do 1 mole of sodium and calcium have different number of atoms?
Answer:
No, they have same number of atoms.

Question 54.
Lead nitrate solution and sodium chloride solution taken in separate beakers. The beakers were weighed and mixed in one beaker and the beaker was weighed again. Does weight remains unchanged or not? On what principle, the answer is based upon?
Answer:
The weight remains unchanged. It is based upon law of conservation of mass.

Question 55.
28 g of magnesium oxide is produced by the combination of 12 g of magnesium and 16 g of oxygen. Which law is illustrated by this data?
Answer:
Law of conservation of mass.

Question 56.
Do 1 mole of Na and 02 have same mass?
Answer:
No, 1 mole of Na has mass = 23 g
1 mole of O₂ has mass = 32 g

Question 57.
1 mole represents particles …………. .
Answer:
6.022 × 10₂₃.

Question 58.
The molar mass of NH3 is
Answer:
17 g.

Question 59.
An element Z has a valency of 3. Write down the formula of its oxide?
Answer:
Z₂O₃.

Question 60.
How many atoms are present in 0.012 kg of C¹² – isotope? What is this number called?
Answer:
6.022 × 10²³ atoms. This number is called Avogadro’s number.

Question 61.
Write down the formula of compound made up of Al³⁺ and [latetx]\mathrm{SO}_{4}^{2-}[/latex].
Answer:
Al₂ (SO₄)₃

Question 62.
How many molecules are present in 9 g of water?
Answer:
9/18 × 6.0222 × 10₂₃ = 3.011 × 10₂₃ molecules.

Question 63.
What is the molecular mass of HN03. (Atomic masses, H = lu, N = 14u, 0 = 16u)
Answer:
1 + 14 + 3 × 16 = 1 + 14 + 48 = 63u.

Question 64.
What are polyatomic ions?
Answer:
It is a group of atoms having net charge, e.g. NH⁺₄, CO₃^2- etc.

Question 65.
The molecular formula of aluminium sulphate is ……….. .
Answer:
Al₂(SO₄)₃

Punjab State Board PSEB 9th Class Science Important Questions Chapter 2 Is Matter Around Us Pure Important Questions and Answers.

PSEB 9th Class Science Important Questions Chapter 2 Is Matter Around Us Pure

Long Answer Type Questions:

Question 1.
(a) Define mixture. Give examples.
(b) What are the types of mixtures?
Answer:
(a) Mixture. It is a product obtained by mixing two or more substances (elements and / or compounds) in any proportion. For example,

1. Air is a mixutre of nitrogen, oxygen, carbon dioxide, water vapour etc.
2. Smoke is a mixture of carbon particles and air.
3. Gun Powder is a mixture of nitre, sulphur and charcoal.
4. Brass is a mixture of copper and zinc.

(b) Types of mixtures. Mixtures are of two types:
1. Homogeneous mixtures and
2. Heterogeneous mixtures.
1. Homogeneous mixtures: A mixture in which the different constitutents are mixed uniformly and has the uniform composition throughout is called homogeneous mixture, e.g. Brass is a homogeneous mixture of copper and zinc, an aqueous solution of sodium chloride is a homogeneous mixture of sodium chloride and water.
2. Heterogeneous mixtures: A mixture in which the different constitutents are not mixed uniformly is called heterogeneous mixture, e.g. soil is a heterogeneous mixture, a mixture of common salt, sand and sulphur is a heterogeneous mixture.

Question 2.
Give important characteristics of a mixture.
Answer:
The important characteristics of a mixure are:

1. In a mixture, the components, elements or compounds are present in no fixed ratio.
2. A mixture is formed from its components as a result of physical change.
3. The properties of a mixture lie between those of its constituents.
4. A mixture may be homogeneous or heterogeneous.
5. The constituents of a mixture can be separated by physical methods only.
6. The formation of a mixture from its constituents does not involve any energy change.

Question 3.
What are the various types of binary solutions based upon the physical states
of solute and solvent?
Answer:
These are of nine types:

Solute	Solvent	Type of solution	Example
1. Solid	Solid	Solution of solid in solid	Brass
2. Solid	Liquid	Solution of solid in liquid	Sugar in water
3. Solid	Gas	Solution of solid in gas	Iodine in air
4. Liquid	Solid	Solution of liquid in solid	CuS04. 5H20
5. Liquid	Liquid	Solution of liquid in liquid	Ethyl alcohol in water
6. Liquid	Gas	Solution of liquid in gas	Moisture in air
7. Gas	Solid	Solution of gas in solid	Hydrogen in palladium
8. Gas	Liquid	Solution of gas in liquid	Carbon dioxide dissolved in water
9. Gas	Gas	Solution of gas in gas	Air

Question 4.
State briefly how would you separate or name the process use to separate:

1. Common salt from a solution of common salt and water.
2. Alcohol from a mixture of alcohol and water.
3. Sulphur from a mixture of carbon particles and powdered roll sulphur.
4. The coloured dyes in black ink.

Answer:

1. The solution containing common salt in water is concentrated and is then cooled. The crystals of common salt are formed which can be separated by filtration.
2. Alcohol can be separated from water by fractional distillation as the two liquids differ much in their boiling points.
3. The mixture is treated with carbon disulphide which dissolves powdered sulphur in it. It is filtered to separate carbon particles. The filtrate upon concentration and cooling gives crystals of sulphur which can be separated by the process of filtration.
4. The coloured dyes in black ink can be separated by the process of paper chromatography.

Question 5.
Give important differences between a compound and a mixture.
Answer:

Compound

Mixture

1. A compound is formed from its constituent elements as a result of chemical reaction. 2. A compound is always homoge­neous in nature. 3. In a compound the elements are present in a fixed ratio by weight. 4. The components of a compound can’t be separated by physical methods but can be separated by chemical methods only. 5. The properties of a compound are different from that of its elements. 6. The formation of a compound from its elements is accompanied by energy changes.

1. A mixture is obtained from its (elements, compounds) components as a result of physical change. 2. The mixtures can be homogeneous or heterogeneous. 3. In a mixture the components can be present in any ratio. 4. The components of a mixture can be separated by physical methods only. 5. The properties of a mixture lie between those of its components. 6. The formation of a mixture from its constituents is not accompanied by energy changes.

Question 6.
How are mixtures classified on the basis of their physical states?
Answer:
On the basis of their physical states, the mixtures are of the following types

Constituents of mixture	Nature of mixture	Example
1. Solid-Solid mixture	Homogeneous	Brass
2. Solid-Solid mixture	Heterogeneous	Common salt and sand
3. Solid-Liquid mixture	Homogeneous	Sugar in water
4. Solid-Liquid mixture	Heterogeneous	Sulphur in water
5. Liquid-Liquid mixture	Homogeneous	Water and alcohol
6. Liquid mixture	Heterogeneous	Carbon tetrachloride and water
7. Liquid-gas mixture	Homogeneous	Carbon dioxide dissolved in water
8. Gas-Gas mixture	Heterogeneous	A mixture of Nitrogen and Oxygen

Question 7.
Explain the following:
(a) Fractional crystallisation
(b) Sublimation
(c) Filtration
Answer:
(a) Fractional Crystallisation. The process of separation of components of a mixture having different solubilities in the same solvent is called fractional crystallisation. This method is used for the separation of components of a mixture which are soluble in the same solvent on heating but have different solubilities.
For example, a mixture of potassium nitrate and sodium chloride can be separated by this method.

This can be explained as follows:
The mixture is dissolved in water. The solid is concentrated to the crystallisation point. On cooling the crystals of less slouble component i.e., sodium chloride appear first. These are separated. On further cooling the crystals of more soluble component i.e., of potassium nitrate will appear. The pure crystals can be obtained by recrystallisation from the same solvent i.e, water.

(b) Sublimation: This method is used for the separation of the components of a mixture in which one component undergoes sublimation whereas other does not. For example, a mixture of ammonium chloride and common salt can be separated by this purpose take the mixture of ammonium chloride and common salt in a china dish. Cover it with an inverted funnel and its open end is to be closed with cotton wool. The walls of china dish are kept booled. On heating, ammonium chloride sublimes and condenses on the cooler parts whereas common salt is left behind. The fine powder of ammonium chloride deposited on the funnel is scrapped with the help of a knife.

Similarly, the mixture of iodine and sand can be separated by this method in which iodine sublimes whereas sand does not.

(c) Filtration. In this method, the mixutre is dissolved in a suitable solvent in which one component dissolves whereas other does not.

For example, a mixture of charcoal and sulphur can be separated by this method. The mixture is treated with carbon disulphide which dissloves sulphur whereas charcoal is left behind. The insoluble charcoal is separated by filtration and is dried. From the filtrate, sulphur can be obtained by evaporating carbon disulphide.

Question 8.
Explain the process of:
1. Distillation
2. Evaporation
Answer:
1. Distillation: The process of converting a liquid into gaseous state by heating to boiling point and condensing the vapour to get the pure liquid is called distillation.
For example, salt can be separated from sea water by this method. For this purpose the apparatus is fitted as shown below:

The mixture of solid and liquid is taken in a distillation flask. On heating vapour of liquid (water) are produced. These are condensed in water condenser and collected in a receiver. The non-volatile sodium chloride is left behind. Similar, a mixture of methyl alcohol and iodine i an be separated by this method.

2. Evaporation: Evaporation is a process of changing a liquid into its gaseous state by heating it at a temperature below its boiling point. For example, common salt can be obtained from a mixture of common salt and water by evaporation.

The mixture is heated in a china dish using sand bath when water vaporises whereas common salt is left behind.

Question 9.
What is chromatography? Why is it regarded as superior method of purification?
Answer:

• Chromatography. The process of separation of different components of a mixture by adsorbing them over a suitable material (called adsorbent) is called chromatography.
• Originally, this technique was used to separate coloured mixtures but now-a-days this method can be used for colourless as well as coloured substances.

The main advantages of this technique are:

1. It can be applied to separate the mixture even if very small amount of mixture of the substances is available.
2. The components of a mixture don’t get wasted during separation.
3. It also helps in estimating the constituents of a mixture apart from separation.

Question 10.
What is the principle of chromatographic separation? Name the different types of chromatography commonly used.
Answer:
Chromatography is based upon the distribution of the mixture of the components between the two phases i.e. a stationary phase and a moving phase. The moving phase consists of mixture of the substances to be separated. The moving phase is applied over a solid or liquid i.e., a stationary phase. The stationary phase separates the components of the mixture by the phenomenon of either partition, adsorption or ion exchange. The different chromatographic techniques are:
(a) Column chromatography
(b) Thin layer chromatography
(c) Ion exchange chromatography
(d) Paper chromatography.

Question 11.
How will you separate gas-gas mixtures?
Answer:
The gas-gas mixtures can be separated by the following method:
Fractional evaporation of mixture of liquefied gases. The mixture of two gases is liquefied by applying high pressure and then allowing it to expand. For example, when air is liquefied under high pressure and allowed to stand, both oxygen and nitrogen get liquefied.

The above liquid mixture is maintained at a temperature of -196°C (b.pt. of liquid N₂), nitrogen boils off. For example, a mixture of carbon dioxide and hydrogen can be separated by passing through porous partitions as showm below.

In this case, H₂ being lighter diffuses at a faster rate as compared to CO₂.

Question 12.
What are the various types of colloidal solutions based upon the physical states of dispersed phase and dispersion medium? Give one example in each case.
Answer:
These are of eight types:

Dispersed Phase	Dispersion Medium	Type or name of colloidal solution	Examples
1. Solid	Solid	Solid sol	Some coloured glasses
2. Liquid	Solid	Gel	Cheese, butter
3. Gas	Solid	Solid foam	Sponge, rubber foam
4. Solid	Liquid	Sol	Mud, milk of magnesia
5. Liquid	Liquid	Emulsion	Milk, hair cream
6. Gas	Liquid	Foam	Froth, whipped cream
7. Solid	Gas	Solid aerosol	Smoke
8. Liquid	Gas	Liquid aerosol	Fog, mist

Question 13.
Define concentration of a solution. How is concentration of a solution expressed?
Answer:
Concentration of a solution. It indicates the amount of solute dissolved per unit mass or volume of solvent or solution.
The concentration of a solution can be expressed as

Question 14.
Describe how you would separate the constituents of the following mixtures in a reasonably pure state:
(a) Sand and iodine
(b) Water and sugar
(c) Ingredients of gun powder
(d) Sulphur, sand and common salt
(e) Carbon dioxide and carbon monoxide.
Answer:
(a) Sand and iodine. The mixture can be separated by sublimation when iodine sublimes whereas sand is left behind.

(b) Water and sugar. Sugar and water can be separated by evaporation when water evaporates and sugar is left behind.

(c) Ingredients of gun powder. Gun powder is a mixture of sulphur, nitre and charcoal. Shake the mixture with water. Nitre passes into solution separated by filtration. Evaporate the filtrate. We get pure nitre.
Shake the residue obtained above with carbon disulphide when sulphur dissolves while charcoal is separated by filtration. From filtration sulphur is obtained by evaporating carbon disulphide.

(d) Sulphur, sand and common salt. Shake the mixture with water and filter. Common salt passes into solution. The filtrate is evaporated to get common salt.
Shake the residue obtained above with carbon disulphide and filter sulphur goes into the filtrate. Evaporate it when sulphur is left behind. Sand is left behind insoluble in carbon disulphide.

(e) Carbon dioxide and carbon monoxide. The mixture can be separated by diffusion through a porous pot when carbon monoxide differ faster than carbon dioxide and thus get separated.

Question 15.
What is paper chromatography? How will you separate the coloured constituents present in a mixture of ink and water?
Answer:
The process of separation of different dissolved components of a mixture by adsorbing them on a suitable material (called adsorbent) is called chromatography. The adsorbent can be solid or liquid. For example, alumina, magnesium oxide, special filter paper.
The components of a mixture are generally dissolved in a solvent like water, alcohol etc. If a filter paper is used as an adsorbent for the separation of components of a mixture, this technique is called paper chromatography.

The process of separation of coloured constituents present in a mixture of ink and water is described ahead:
1. Take a special filter paper about 25 cm long and 4 cm broad and stick it to a glass rod at its one end with the help of gum as shown below. Mark a line at a distance of 3 cm from the lower end with the help of pencil. Put a drop of ink at the centre of this line with the help of a fine capillary.
2. Dip this end in water taken in a beaker upto 2 cm.
3. Suspend this filter paper in a tall cylinder and allow it to stand undisturbed for one hour. The water rises up the filter paper and reaches the ink drop, dissolves its components and rise upwards along with water. The different components of ink are adsorbed upto different extents on the filter paper, therefore, they travel different distances on the filter paper.
4. After one hour, the filter paper is taken out and dried. Different of colours corresponding to the components of ink are produced on the filter paper. This filter paper is called chromatograph.

Question 16.
Briefly describe simple methods of separating the following mixtures:
(a) Powdered chalk and sugar
(b) Nitre and common salt
(c) Iron and copper filings
(d) Ammonium chloride, sand and common salt
(e) Ammonia and hydrogen.
Answer:
(a) Powdered chalk and sugar can be separated by using water which dissolves sugar and chalk is insoluble. It is separated by filtration. From sugar solution, sugar is obtained by evaporating water.

(b) Nitre and common salt. The mixture can be separated by fractional crystallisation from the solutions in water because they have different solubilities in water.

(c) Iron and copper filings can be separated by using a magnet when iron filings cling to magnet whereas copper filings don’t.

(d) Ammonium chloride, sand and common salt. Ammonium chloride is separated by sublimation. Sand and common salt are separated by using water when sand remains insoluble and is separated by filtration, From aqueous solution, sodium chloride can be separated by evaporation.

(e) Ammonia and hydrogen can be separated by diffusion through porous pot. Ammonia and hydrogen have different rates of diffusion due to different densities.

Question 17.
How will you separate liquid-liquid mixture or immiscible liquids?
Answer:
The liquid-liquid mixtures can be separated by using :
1. Separating funnel.
2. Fractional distillation.
1. Separation of liquid-liquid mixture by using separating funnel. This method is used when the two liquids are immiscible. For example, a mixture of carbon disulphide and wrater can be separated by this method.

The mixture is taken in a separating funnel. The funnel is allowed to stand for sometime. On standing, the liquid having higher density forms the lower layer whereas the liquid having lower density forms the upper layer. The two liquids are taken out from the separating funnel in separate conical flask.

2. Separation of liquid-liquid mixture using fractional distillation:

The process of separating the mixture of two immiscible liquids by using distillation carried out with the help of a long fractionating column is called fractional distillation.
For example, a mixture of ethyl alcohol and water can be separated by this method. The apparatus is fitted as shown below:

The mixture of ethyl alcohol anci water is heated in a distillation flask fitted with a fractionating column. On heating the vapour of liquid having lower boiling point are produced first and condensed in the water condenser and collected in a receiver. When the temperature of thermometer begins to rise, the vapour of other liquid are produced and these are condensed and collected in a separate receiver.

Question 18.
How will you separate the solid-liquid mixtures?
Answer:
The solid-liquid mixtures can be separated by the following methods:
1. By sedimentation and decantation. In this method, the mixture is allowed to stand when the solid particles settle down as sediment whereas clear liquid is left behind which is poured out carefully. This process is called decantation e.g. mixture of sand and water can be separated by this method. By this method, the complete separation is not possible.

2. By filtration. In this method, the mixture can be separated by using filter paper when the insoluble solid is left on the filter paper whereas the clear liquid passes out from the filter paper and is collected. For example, a mixture of chalk and water can be separated by this method.

Short Answer Type Questions:

Question 1.
Give three characteristics of a pure substance.
Answer:

1. It is homogeneous.
2. It has a definite set of properties.
3. A pure substance cannot be separated into other kinds of matter by any known physical method.

Question 2.
Give three examples each of two classes of pure substances.
Answer:
Pure substances are of two types:
(a) Elements e.g. carbon, nitrogen, oxygen etc.
(b) Compounds e.g. ammonium, water, carbon dioxide etc.

Question 3.
Give three characteristics of a mixture.
Answer:
(a) The components of a mixture are present in any ratio.
(b) It can be homogeneous or heterogeneous.
(c) The mixture can be separated with its constituents by physical or mechanical methods only.

Question 4.
Name the methods commonly used for separation of components of a mixture.
Answer:
These are:

1. Evaporation
2. Crytallisation
3. Centrifugation
4. Using separating funnel
5. Simple distillation
6. Fractional distillation
7. Chromatography
8. Sublimation

Question 5.
Define colloidal solution.
Answer:
It is a heterogeneous mixture or solution in which the particles having size 1 to 100 11m are suspended in a suitable solvent or dispersion medium. For example, starch solution.

Question 6.
Define dispersed phase and dispersion medium.
Answer:

• Dispersed phase: In the colloidal solution colloidal particles constitute dispersed phase.
• Dispersion medium: In the colloidal solution the medium in which colloidal particles are dispersed in called dispersion medium.
• e.g. in the colloidal solution of starch in water, starch particles constitutes dispersed phase and water constitutes dispersion medium.

Question 7.
From the methods (or techniques) of distillation, filtration, fractional distillation, chromatography, crystallisation, select and write down the technique you would use to separate:

1. Constituents of colouring matter in ink.
2. Hydrated copper (II) sulphate or blue vitriol from its aqueous solution.
3. Nitrogen from liquid air.
4. Unused zinc after the reaction of excess of zinc with dilute sulphuric acid.

Answer:

1. Chromatography
2. Crystallisation
3. Fractional distillation
4. Filtration.

Question 8.
Name the technique which could be used to separate:
1. Iodine crystals from sand
2. Petrol from crude oil.
Answer:
1. Iodine crystals can be separated from sand by sublimation.
2. Petrol can be separated from crude oil by fractional distillation.

Question 9.
How will you separate:
1. Pure water from sea water?
2. Kerosene oil from a mixture of kerosene oil and petrol?
Answer:
1. It can be obtained by the process of distillation. When sea water is distilled, water distils, and vapour are condensed in a receiver whereas common salt is left behind in the retort.
2. Kerosene oil can be separated from a mixture of kerosene oil and petrol by fractional distillation when petrol distils off first and then kerosene oil distils off. .

Question 10.

1. Name the kind of change of state when naphthalene changes into gaseous state.
2. Name one element which undergoes similar change as in (i).
3. Name a common substance which exists in all the three states of matter.

Answer:

1. Sublimation
2. Ammonium chloride
3. Water.

Question 11.
Define electrophoresis.
Answer:
Electrophoresis is the process of migration of colloidal particles towards oppositely charged electrode under the influence of an electric field is called electrophoresis. The electrophoresis is due to the charge present on the colloidal particles.

Question 12.
Explain Brownian movement.
Answer:
Brownian movement. When colloidal solutions are viewed with the help of ultra-microscope, it is observed that colloidal particles follow zig-zig path. This is called brownian movement. This effect is due to the unequal impacts of the particles of dispersion medium with colloidal particles.

Question 13.
Explain Tyndall effect.
Answer:
Tyndall effect. If a bright, narrow and convergent beam of light is passed through a colloidal solution and is viewed at right angles with the help of a microscope, the path of light becomes visible and a bright cone of light called Tyndall cone is produced. This luminosity of path of a beam of light in a colloidal solution is called Tyndall effect.

Question 14.
Define physical change and chemical change.
Answer:

• Physical Change. It is a temporary change in which only the physical properties of substances change and it can be easily reversed.
• Examples: Glowing of an electric bulb, evaporation of water.
• Chemical Change: It is a permanent change in which the chemical properties of substances change and there is a change in composition and cannot be reversed.
• Examples: Baking of a cake, Drying of a paint etc.

Question 15.
Classify the following substances into elements, compounds and mixtures:

1. Cane sugar
2. Zinc
3. Oxygen
4. Marble
5. Bronze
6. Nitre
7. Air
8. Milk
9. Iron
10. Stainless steel

Answer:

1. Cane sugar – Compound
2. Zinc – Element
3. Oxygen – Element
4. Marble – Mixture
5. Bronze – Mixture
6. Nitre – Compound
7. Air – Mixture
8. Milk – Mixture
9. Iron – Element
10. Stainless steel – Mixture

Question 16.
1. Name the process used to separate the constituents liquefied air.
2. State how will you remove carbon dioxide from a mixture of carbon dioxide and carbon monoxide.
Answer:
1. Fractional evaporation.
2. Pass the mixture through potassium hydroxide solution. Carbon dioxide is absorbed by KOH solution.
2KOH + C0₂ → K₂C0₃ + H₂0
Carbon monoxide is left behind and is collected over water by downward displacement of water.

Question 17.
How would you separate:
(a) Benzene (b.pt. 80°C) from toluene, methylbenzene (b.pt. 111°C) with which it is miscible?
(b) Kerosene oil from a mixture of kerosene oil and petrol?
(c) Lead sulphate from a mixture of lead sulphate and lead chloride?
Answer:
(a) By using simple distillation when benzene distils off first and its vapours are condensed and collected in a receiver.

(b) Kerosene oil from a mixture of kerosene oil and petrol can be obtained by using separating funnel when kerosene oil forms upper layer.

(c) Lead sulphate from a mixture of lead sulphate and lead chloride can be obtained by boiling with water which dissolves lead chloride and insoluble lead sulphate is separated by filtration.

Question 18.
A molecule can be formed by an element as well as by a compound. Explain.
Answer:
A molecule is the smallest particle of a substance i.e. an element or a compound which can exist freely. It has all the properties of that substance, e.g. a molecule of hydrogen (H₂), a molecule of methane (CH₄).

Question 19.
Can a mixture of chloroform (b.pt. 61°C) and carbon tetrachloride (b.pt. 77°C) be satisfactorily separated by the process you use for separating the various fractions of petroleum?
Answer:
Yes, a mixture of chloroform and carbon tetrachloride can be separated by using fractional distillation as used for the separation of various fractions of petroleum. The heating should be carried out slowly on a sand bath and vapours are condensed in a Liebig condenser and collected in separate receivers.

Question 20.
Name a mixture used:

1. by all living beings
2. in the construction of buildings
3. as a food

Answer:

1. Air
2. Cement
3. Milk

Question 21.
Give two advantages of paper chromatography.
Answer:
1. It can be applied even to a very small amount of the mixture of the substances.
2. The components of a mixture don’t get wasted during separation.

Question 22.
How would you obtain a sample of sulphur from a mixture of sulphur and carbon?
Answer:
Shake the mixture of sulphur and carbon with carbon disulphide and filter. Sulphur will be present in the filtrate and the residue is carbon. The filtrate is evaporated when carbon disulphide vaporises while sulphur is left behind.

Question 23.
How would you obtain pure ammonium chloride when it contains potassium chloride as an impurity?
Answer:
The mixture is heated. Ammonium chloride sublimes and its vapour are condensed in an inverted funnel. Potassium chloride is left behind. From the funnel ammonium chloride is scrapped with a knife.

Question 24.
Name three metals which are liquids at room temperature.
Answer:
These are mercury, cesium and gallium.

Question 25.
Name the various noble gases.
Answer:
The various noble gases are: Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe) and Radon (Rn).

Question 26.
Which of the following statements are correct and which are incorrect?

1. Milk is a mixture.
2. Smoke is a mixture of solids and gases.
3. Ice cream is a mixture.
4. Mercury is a solid
5. Thums up is a homogeneous mixture.

Answer:

1. True
2. True
3. True
4. False
5. True.

Question 27.
If you are given a mixture of hydrogen and carbon dioxide, how would you remove the carbon dioxide gas?
Answer:
The carbon dioxide gas can be removed by passing the gaseous mixture through potassium hydroxide solution which absorbs carbon dioxide and hydrogen gas is set free.

Question 28.
Give two pieces of evidence that sodium chloride is a compound.
Answer:
Sodium chloride is a compound because:
1. in sodium chloride, sodium and chlorine are combined chemically in a fixed ratio by mass.
2. the formation of sodium chloride from sodium and chlorine is accompanied by loss of energy.

Question 29.
Give reasons to show that ammonia is a compound.
Answer:

1. The properties of ammonia are different from those of its components i.e. nitrogen and hydrogen.
2. When ammonia is formed from nitrogen and hydrogen, energy is given out.
3. In ammonia, N and H are present in fixed ratio of 14 : 3 by mass.

Question 30.
Give three reasons why air is considered a mixture and not a compound.
Answer:
In air:

1. the components are not present in any fixed ratio.
2. the properties of air are average of the properties of its components.
3. the components can be separated by physical methods.

Question 31.
Define crystallisation. Give its importance.
Answer:
It is a process in which a pure solid in the form of crystals is separated by cooling its hot saturated solution in a suitable solvent.
Importance:
1. For the purification of salt obtained from sea water.
2. To get crystals of alum from impure samples.

Question 32.
1. Some reduced iron filings and powdered roll sulphur are well mixed and heated in a test tube. Describe all what you observe.
2. Name the grey mass which is formed in test tube at the end of reaction.
3. Would you call the above reaction: exothermic or endothermic?
Answer:
1. When iron filings and powdered roll sulphur are well mixed and heated in a test tube, iron (II) sulphide is produced

2. Grey mass of iron (II) sulphide is produced.
3. The above reaction is endothermic, because heat energy is absorbed.

Question 33.
What are exothermic and endothermic reactions?
Answer:
1. Exothermic reaction: It is a chemical reaction in which heat energy is evolved. e.g. burning of candle.
2. Endothermic reaction: It is a chemical reaction in which heat energy is absorbed e.g. decomposition of calcium carbonate to give calcium oxide and carbon dioxide.

Question 34.
What is the importance of evaporation?
Answer:
It is used to separate the non-volatile component from volatile solvent component from a mixture e.g. dye can be obtained from blue-black ink.

Question 35.
What are the applications of centrifugation?
Answer:

1. It is used in diagnostic laboratories to test blood and urine.
2. It is used in diaries and homes to separate butter from cream.
3. It is used in washing machines to squeeze out water from wet clothes.

Question 36.
How will you separate a mixture of:
(a) Iodine and sand?
(b) Ammonium chloride and common salt?
(c) Chloroform and water?
(d) Carbon disulphide and water?
Answer:
(a) By sublimation
(b) By sublimation
(c) By using a separating funnel
(d) By using a separating funnel.

Question 37.
A solution contains 40 g of NaCl in 320 g of water. Calculate its concentration in terms of mass percentage of solution.
Answer:

• Mass of NaCl = 40g
• Mass of water = 320g
• Total Mass of solution = 40 + 320 = 360g
• Mass percentage of solution = 40 / 360 × 100 = 100 / 9 = 11.1

Question 38.
What are the advantages of crystallisation over evaporation?
Answer:

• Some solids decompose on heating to dryness.
• Some solids like sugar may get charred on heating.
• Some impurities may be present in the solution on dissolving the impure solid in a solvent.

Question 39.
Name the separation technique to separate:

1. Insoluble solid insolvent.
2. Solution of solid in liquid.
3. Miscible mixture of liquids.
4. Immiscible mixture of liquids.
5. Mixture of two solids, one of which sublimes

Answer:

1. Filtration, centrifugation
2. Evaporation, crystallisation, distillation
3. Distillation, fractional distillation
4. Separating funnel
5. Sublimation

Question 40.
What is fractional distillation? Give its importance.
Answer:
Fractional distillation. It is the process of separation of a mixture of two or more miscible liquids having very close boiling points (differing by less than 25°C). In this case, distillation is carried out using a fractionating column.
Importance:
1. This process is ised in the separation of petroleum products.
2. It is used to get component gases from air.

Question 41.
A solution of acetone in water contains 5 ml is 50 ml of its aqueous solution. Calculate the volume percentage of the solution.
Answer:

1. Volume of solute = 8ml
2. Volume of solution = 50ml
3. Volume percentage of solution 5/50 × 100 = 10

Question 42.
Define distillation and give its importance.
Answer:
The conversion of a liquid into vapour and condensing the vapours back into liquid is known as distillation.
Importance:
1. To separate two miscible liquids which boil without decomposition and have sufficient differences in their boiling points (more than 30°C).
2. To separate a volatile component of a solution from a non-volatile component.

Question 43.
How are elements classified?
Answer:
The elements can be classified as:
(a) Metals e.g. Cu, Ag etc.
(b) Non-metals e.g. C, S etc.
(c) Metalloids e.g. As, Sb etc.
(d) Noble gases e.g. He, Ne etc.

Question 44.
Which of the following are pure substances and which are mixtures?

1. Air
2. Milk
3. Graphite
4. Gasoline
5. Distilled water
6. Ice
7. Iodised table salt
8. Diamond
9. Oxygen
10. One rupee coin
11. 22 Carat gold
12. 24 Carat gold
13. Steel
14. Iron
15. Solid Iodine

Answer:

1. Air – Mixture
2. Milk – Mixture
3. Graphite – Pure substance
4. Gasoline – Mixture
5. Distilled water – Pure substance
6. Ice – Pure substance
7. Iodised table salt – Mixture
8. Diamond – Pure substance
9. Oxygen – Pure substance
10. One rupee coin – Mixture
11. 22 carat gold – Mixture
12. 24 carat gold – Pure substance
13. Steel – Mixture
14. Iron – Pure substance
15. Solid Iodine – Pure substance

Question 45.
Which one of the substances given ahead is an element, a mixture or a chemical compound. Give one reason in each case:
(a) chlorine
(b) milk
(c) honey
(d) flowers of sulphur
(e) seawater
(f) gun powder
(g) brine
(h) sulphur
(i) apple juice
(j) carbon dioxide
(k) air
(Z) syrup.
Answer:
(a) Chlorine. It is an element made up of only one kind of atom.
(b Milk. It is a mixture of fat, water etc.
(c )Honey. It is a mixture of carbohydrates.
(d Flowers of sulphur. It is an element made up of only sulphur molecules (S8).
(e )Sea Water. It is a mixture of water and dissolved salts.
(f) Gun powder. It is a mixture of sulphur, nitre and charcoal.
(g) Brine. It is a mixture of water and sodium chloride.
(h) Sulphur. It is an element made up of sulphur molecules (S8).
(i) Apple juice. It is a mixture.
(j) Carbon dioxide. It is a compound of carbon and oxygen combined together in the fixed ratio 3 : 8 by mass.
(k) Air. It is a mixture of oxygen, nitrogen and other gases.
(Z) Syrup. It is a mixture.

Question 46.
(a) Name a chemical technique which could be used successfully to separate
1. Iodine crystals from sand.
2. Petrol from kerosene oil.
(b) A pupil decides to separate powdered calcium carbonate from powdered calcium chloride by shaking the mixture with water and filtering. Would this procedure succeed? Explain your answer.
(c) Mixtures are usually heterogeneous, but sometimes homogeneous also.
Give one example each of two different types of mixtures.
Answer:
(a) 1. Sublimation
2. Fractional distillation
(b) Yes, when a mixture of calcium carbonate and calcium chloride is treated with water, calcium chloride dissolves whereas calcium carbonate does not. It is separated by filtration.
(c) Homogeneous mixture, e.g. Brass is a homogeneous mixture of copper and zinc.
Heterogeneous mixture, e.g. common salt and sand.

Question 47.
From the following techniques:
Distillation, filtration, fractional distillation, chromatography, crystallisation, sublimation, evaporation, decantation, sedimentation. Select the method you will use to separate:
(a) the constituents of the colouring matter of ink.
(b) hydrated CuS04 from its aqueous solution.
(c) Grass stains.
(d) Common salt from sea-water.
(e) Petrol from crude oil.
Answer:
(a) Chromatography
(b) Crystallisation
(c) Chromatography
(d) Evaporation
(e) Fractional distillation.

Question 48.
How will you separate a mixtu funnel? Explain with an activity.
Answer:
Take a clean separating funnel and take a mixture of mustard oil and water in it. Allow it to stand for sometime. On standing, two separate layers appears. The lower layer is of water (heavier) and the upper layer is of mustard oil (lighter).

Open the stop cock of the separating funnel and pour out the lower layer of water carefully. Close the stop cock when the water has been removed. Mustard oil is left in the separating funnel.

Very Short Answer Type Questions:

Question 1.
Define pure substance.
Answer:
It is a material containing particles of only one kind having a definite set of properties.

Question 2.
Define mixture.
Answer:
It is a material obtained by mixing two or more elements and or compounds in any ratio.

Question 3.
How will you separate the components of an aqueous solution of sodium chloride?
Answer:
By simple distillation.

Question 4.
Give two examples of homogeneous mixture.
Answer:
Sodium chloride dissolved in water, sugar dissolved in water.

Question 5.
Give two examples of homogeneous mixtures.
Answer:
Iron filings and common salt, common salt and sulphur.

Question 6.
Is the mixture of oil and water, homogeneous or heterogeneous?
Answer:
Heterogeneous.

Question 7.
What is solution?
Answer:
It is a homogeneous mixture of two or more substances whose composition can be changed within certain fixed limits.

Question 8.
Give examples of solid solution.
Answer:
Brass, Bronze.

Question 9.
Give one example of gaseous solution.
Answer:
Air.

Question 10.
Name the components of Brass.
Answer:
Zinc and copper.

Question 11.
Define solute.
Answer:
It is the component of a solution which is present in small amount and which is dissolved in another component called solvent.

Question 12.
Define solvent.
Answer:
It is the component of solution which is present in large amount and in which solute is dissolved.

Question 13.
Name the solute and solvent in an aqueous solution of sugar.
Answer:
Water-Solvent, Sugar-Solute.

Question 14.
In tincture of Iodine, name solute and solvent.
Answer:
Solute-Iodine, Solvent-Alcohol.

Question 15.
In soda water, name solute and solvent.
Answer:
Solute-Carbon dioxide, Solvent-water.

Question 16.
What is the type of air mixture?
Answer:
Homogeneous.

Question 17.
In air name solute and solvent?
Answer:
Solvent-Nitrogen, Solute-Oxygen and other gases.

Question 18.
What is the size of particles of solutions?
Answer:
Less than lnm (10^-9m).

Question 19.
What is saturated solution?
Answer:
It is a solution in which no more of solute can be dissolved at the given temperature and pressure.

Question 20.
What is unsaturated solution?
Answer:
It is a solution in which more of solute can be dissolved at the given temperature and pressure.

Question 21.
What is the concentration of a solution?
Answer:
It gives us the exact amount of solute dissolved in an exact amount of solvent or solution.

Question 22.
What is a suspension?
Answer:
It is a heterogeneous mixture in which small particles of a solid don’t dissolve but remain suspended in the liquid (or gas).

Question 23.
Why is suspension temporary?
Answer:
This is because components of suspension can be saparated by filtration.

Question 24.
Suspended particles in a suspension can be seen with naked eye, why?
Answer:
This is because their sizes are more than 100 run.

Question 25.
What is Tyndall effect?
Answer:
It is the scattering of light by colloidal particles.

Question 26.
How will you prove that milk is a colloidal solution?
Answer:
It shows Tyndall effect.

Question 27.
What is the size of colloidal particles?
Answer:
1 to 100 nm.

Question 28.
How will you separate colloidal particles from solution?
Answer:
By ultra centrifugation.

Question 29.
When do we don’t use filtration?
Answer:
If the solid particles present in solution have very small sizes and can pass through pores of filter paper.

Question 30.
What is the principle of centrifugation of mixtures?
Answer:
Heavier particles settle down and lighter particles float over them.

Question 31.
Where do we use centrifugal machine?
Answer:
In diagnostic laboratory to study urine and blood, in dairies to separate butter and cream from milk, to squeeze water from clothes in washing machine.

Question 32.
On the basis of what principle, two immiscible liquids can be separated?
Answer:
Based upon density.

Question 33.
How can a mixture of sodium chloride and ammonium chloride separated?
Answer:
By sublimation.

Question 34.
Name four substances which undergo sublimations.
Answer:
Ammonium chloride, comphor, naphthalene, anthracene.

Question 35.
How many colours are mixed in a dye?
Answer:
Two or more colours.

Question 36.
Define chromatography.
Ans.wer:
It is the separation of coloured components of a mixture based upon adsorption.

Question 37.
What are the uses of chromatography?
Answer:
1. To separate components of a dye.
2. To separate colours from natural colours, to separate sugar from urine and to separate medicine from blood.

Question 38.
Which type of liquid mixture solutions can be separated by simple distillation?
Answer:
Liquids having large differences in their boiling points.

Question 39.
Which type of liquid mixture solutions are separated by fractional distillation?
Answer:
Liquids whose boiling points differ by less than 25 K.

Question 40.
Give two examples where fractional distillation is used to separate the components of a mixture.
Answer:
Air, petroleum.

Question 41.
What is the function of glass beads in fractionating column?
Answer:
These provide surface for cooling and condensing vapours.

Question 42.
Which type of mixture air is?
Answer:
It is a homogeneous mixture.

Question 43.
What is the boiling point of oxygen?
Answer:
183°C.

Question 44.
What is the boiling point of Argon.
Answer:
186°C.

Question 45.
What is the boiling point of nitrogen?
Answer:
196°C.

Question 46.
When do we use crystallisation for purification?
Answer:
To purify solids.

Question 47.
How will you get pure copper sulphate?
Answer:
By crystallisation.

Question 48.
Why is crystallisation better than simple distillation?
Answer:
In simple distillation, some substances decompose or are burnt and some impurities are left.

Question 49.
How will you get pure water from sea water?
Answer:
By evaporation and simple crystallisation.

Question 50.
How is alum purified?
Answer:
By crystallisation.

Question 51.
What are the changes during chemical change?
Answer:
Chemical decomposition and change of chemical properties.

Question 52.
Name the type of change of combustion?
Answer:
Chemical change.

Question 53.
How is matter classified on the basis of chemical decomposition?
Answer:
Elements and compounds.

Question 54.
Which French scientist proved that element is a fundamental or basic particle of matter?
Answer:
Antonie Lorentz Lavosier.

Question 55.
Which is the basic unit of matter?
Answer:
Element.

Question 56.
Define an element.
Answer:
It is the smallest particle of an element which can’t be decomposed into still smaller particles by chemical reaction.

Question 57.
How are elements classified?
Answer:
Metals, non-metals and metalloids.

Question 58.
Name the metal which is liquid at room temperature.
Answer:
Mercury.

Question 59.
What is metalloid?
Answer:
It shows the properties of both metals and non-metals.

Question 60.
Give two examples of metalloids.
Answer:
Arsenic, antimony.

Question 61.
Give examples of non-metals.
Answer:
Carbon, hydrogen, oxygen, chlorine, bromine etc.

Question 62.
Give examples for metals.
Answer:
Sodium, potassium, copper, iron, gold, silver etc.

Question 63.
How many elements are known till today?
Answer:
112.

Question 64.
How many elements occur in nature?
Answer:
There are 92 natural elements.

Question 65.
How many elements are gases at room temperature?
Answer:
11.

Question 66.
Name five methods to separate mixtures.
Answer:

1. Filtration
2. Crystallisation
3. Sublimation
4. Evaporation
5. Distillation.

Question 67.
How are sugar crystals separated in a sugar factory?
Answer:
By centrifugation process.

Question 68.
The size of colloidal particals is in the range …………….. .
Answer:
1 to 100 run.

Question 69.
Tyndall effect is shown by ……………. .
Answer:
Colloidal particles.

Question 70.
He and Ne are ……………….. gases.
Answer:
Noble.

Question 71.
FeS + H₂S0₄ → …………..
Answer:
FeS + H₂S0₄ → FeS0₄ + H₂S

Question 72.
In a refinery, petrol is obtained from crude oil by the process of …………… .
Answer:
Fractional distillation

Question 73.
Grass stains are removed from the clothing by using ……………. as solvent.
Answer:
Methylated spirit

Question 74.
Common salt is obtained from sea water by the process of ……………. .
Answer:
Evaporation

Question 75.
When caustic soda solution is added to an aqueous solution of copper sulphate, a blue precipitate of copper hydroxide is obtained. The copper hydroxide can be separated from the mixture by the process of ……………….. .
Answer:
Filtration.