PSEB Notes

This PSEB 6th Class Science Notes Chapter 5 Separation of Substances will help you in revision during exams.

PSEB 6th Class Science Notes Chapter 5 Separation of Substances

→ Substances around us can be pure substances or impure substances. Impure substances are also known as mixtures.

→ A pure substance is made up of only one type of atom or molecule, e.g. water. It has definite composition and properties.

→ Some mixtures have some desired substances and undesired substances.

→ We must separate undesired substances from desired substances.

→ The process of separating different substances from a mixture is known as separation.

→ The separation must be done if it has undesired substances. This is because undesired substances in the mixture can be harmful to us.

→ Separation is important in those cases where we need a particular component in a pure state.

→ We have many methods for separating components of a mixture.

→ These are based upon differences in the properties of substances present in the mixture.

→ Different methods of separation are Hand-picking, Threshing, Winnowing, Sieving, Sedimentation, Decantation, Filtration, Evaporation, etc.

→ Hand-picking is used to separate the components of a mixture if we can see these with f naked eye and these are large in size.

→ The combine is used for both the harvesting and threshing process.

→ Threshing is the separation of grains from the chaff. It can be done using any one method out of the three i.e.

• manual
• with the help of Animals
• using machines

→ Winnowing is a method to separate heavier and lighter components of a mixture by wind or by blowing air.

→ Methods like decantation, sedimentation, filtration, evaporation are used to separate mixtures of solids and liquids.

→ The process of settling down heavier, insoluble particles from a mixture is called sedimentation.

→ The substance that settles at the bottom is called sediment.

→ This method is used to separate insoluble heavier particles from a liquid.

→ The process of transferring the clear liquid without disturbing sediment is known as decantation.

→ The process of separating an insoluble solid from a liquid bypassing the liquid through a filter paper or muslin cloth is known as filtration.

→ The process of separating differently sized particles of a mixture using a sieve is called sieving.

→ The process of converting a liquid into its vapours by heating is called evaporation.

→ Sometimes we can or need more than one method for separating components of a mixture.

→ When a mixture of two or more substances appears like a single substance or pure substance it is called a solution.

→ In a solution, the substance present in a larger amount is called the solvent and the substance present in a smaller amount is called the solute.

→ A saturated solution is a solution in which no more solute can be dissolved at a particular temperature.

→ An unsaturated solution is a solution in which more solute can be dissolved at a particular temperature.

→ Water dissolves different amounts of substances in it and the solubility of most substances increases when the solution is heated.

→ Evaporation and condensation are opposite of each other.

→ Pure substance: If a substance is made up of only one type of component (atoms or molecules) it is called a pure substance. It must have definite composition and properties.

→ Impure substance: An impure substance is one that consists of a mixture of different types of molecules.

→ Mixture: A substance made up of two or more elements or compound mixed together in any ratio without any chemical reaction is called a mixture.

→ Solution: When a mixture of two or more substances appears like a single substance or pure substance it is called a solution.

→ Solvent: In a solution, the substance present in a larger amount is called the solvent.

→ Solute: In a solution, the substance present in smaller amounts is called the solute.

→ Saturated solution: A solution in which no more solute can be dissolved at a particular temperature is called a saturated solution.

→ Unsaturated solution: A solution in which more solute can be dissolved at a particular temperature is called a saturated solution.

→ Distillation: The process in which a liquid is converted into vapours by boiling it and the vapours so formed are condensed by cooling to give pure liquid is called distillation.

→ Hand-picking: The method of separating undesirable solid substances or impurities from useful solids by hand is known as handpicking.

→ Winnowing: When the particles of impurities are light or when light and heavy particles from a mixture then the winnowing method is used to separate them.

→ Threshing: The process of separating grains from the stalks is called threshing. In this method, we beat stalks to free the seeds.

→ Sieving: Sieving is a method in which smaller solid particles are separated from bigger and larger solid particles by passing through a sieve.

→ Sedimentation: In this process, the liquid mixture is placed undisturbed for some time. Solid heavy insoluble particles settle down and lighter particles float in the liquid.

→ Decantation: The process of transferring the liquid from the mixture without disturbing sediments is known as decantation.

→ Churning: The process of separation of lighter particles from a liquid mixture is churning.

→ Evaporation: Evaporation is a process in which liquid is converted into its vapours by heating.

→ Condensation: The process of converting water vapours into their liquid form is called condensation.

→ Filtrate: The clean liquid obtained during filtration is known as filtrate.

→ Residue: The sand and mud left on the filter paper is known as the residue.

This PSEB 6th Class Science Notes Chapter 4 Sorting Materials into Groups will help you in revision during exams.

PSEB 6th Class Science Notes Chapter 4 Sorting Materials into Groups

→ The matter is defined as anything that has mass and takes up space.

→ All material around us is matters because all materials occupy space and have mass.

→ Feelings of love or sadness, signals received by radio and television, different forms of energy do not matter.

→ Some of these substances are made up of one material whereas others are made up of more than one material.

→ Atom is the smallest part that is found in all types of matter.

→ We are surrounded by different substances having different shapes, sizes, colours, and uses.

→ Some articles can be made from different materials. There are certain different articles that are made up of the same materials.

→ Due to the large variety of objects, it is better if we classify these. We can classify these different bases i.e. shape, the material used, use, etc.

→ Objects made from one material have simple composition. Objects made from many materials have complex compositions.

→ Materials are used to make objects depending upon their properties and the purpose for which the objects are to be used.

→ Some materials have similar and some have dissimilar properties.

→ Some substances completely disappear when dissolved in water. These are called soluble substances.

→ Substances that do not mix with water or do not disappear in water even after stirring for a long time are called insoluble substances.

→ Some materials have a shining appearance. These are called lustrous.

→ The substances which have a dull appearance are called non-lustrous substances.

→ Some materials are hard. These are called rigid substances.

→ We can see across certain substances these are called transparent substances.

→ We cannot see across certain substances. These are called opaque substances.

→ We can see only up to a certain extent across some substances. These are called translucent substances.

→ Liquids that completely mix with each other are called miscible liquids.

→ Liquids that do not mix with each other are called immiscible liquids.

→ Liquids that partially mix with each other are called partially miscible liquids.

→ The mass per unit volume of a substance is known as density.

→ If an insoluble substance has a density higher than water then it will sink.

→ If an insoluble substance has a density lower than water then it will float.

→ Out of a pair of immiscible liquids, the one with the higher density will form the lower layer and the one with the lower density will form the upper layer.

→ Miscible: The liquids which mix completely are called miscible liquids.

→ Immiscible: The liquids which do not mix with each other are called miscible liquids.

→ Soluble: The solid substance that on dissolving in water or any other liquid completely disappear is called a soluble substance.

→ Insoluble: The solid substance that on dissolving in water or any other liquid that does not disappear is called an insoluble substance.

→ Transparent: The substances through which one can see, are called transparent.

→ Opaque: The substances through which one cannot see are called opaque.

→ Translucent: The substances through which one can see partially but not clearly, are called translucent.

→ Lustre: The shining that we see on a substance is called lustre.

→ Atom: The smallest part of the matter is known as an atom.

→ Texture: It means how we feel upon touching the surface of a substance.

→ Rigid: It means whether a substance can be compressed or not.

→ Density: The mass per unit volume of a substance is known as density.

This PSEB 6th Class Science Notes Chapter 3 Fibre to Fabric will help you in revision during exams.

PSEB 6th Class Science Notes Chapter 3 Fibre to Fabric

→ Clothes are important as they

• protect us from sunlight, wind, cold, heat, rain, etc.
• help us to feel comfortable in different weather conditions and to look smart.

→ People commonly wear different types of clothes like sari, coat-pent, suits, jeans,I shirts, T-shirts. Turban, kurta-pajama, salwar-kameez, lungi, dhoti, etc.

→ Cotton, silk, wool, and polyester are different variety of clothing materials, called fabrics.

→ Bedsheets, blankets, towels, curtains, duster, floor mats, our school bags, belts, socks, ties are made up of different kinds of fabric. Thus, different kinds of fabrics are used! to make different types of clothes.

→ Yarn is a thin thread used for making different fabrics. It is made from fibre.

→ Fibres are of two types:

• natural
• man-made (Synthetic).

→ Fibres that are obtained from nature are called natural fibre.

→ Natural fibres can be obtained from plants and animals.

→ Fibres obtained from plants are called plant fibres.

→ Similarly, fibres obtained from animals are called animal fibres.

→ Cotton, Jute, and coir are examples of plant fibres whereas wool, silk, etc. are examples of animal fibres.

→ Ginning, spinning, weaving, knitting, etc. are some processes that are used to make fabric or clothing material from cotton fibre.

→ The fibres made by man from, chemicals are called synthetic fibers.

→ Nylon, acrylic, and Polyester are examples of synthetic fibres.

→ Synthetic fibre is used to make socks, toothbrush bristles, car seat belts, carpets, ropes, school bags, etc.

→ Jute fibre is obtained from the stem of the jute plant by the process of retting.

→ Synthetic fibres dry easily, have lesser air spaces between them, are stronger and wrinkle-free.

→ Synthetic fibres do not absorb water, so these fibres are not suitable for hot and humid weather.

→ Cotton clothes are good for humid and hot weather. It absorbs water easily.

→ The process of separating cotton fibres from the seeds by combing is called ginning Removing of wool from sheep using clippers is called shearing.

→ The rearing of silkworms to produce silk.

→ The process of arranging two sets of yarn together to make a fabric is called weaving.

→ In contrast, a single yam is used to make a piece of fabric in knitting.

→ Knitting is done by hands or by machines.

→ Yarn: Yarn is a thin thread used for making different fabrics.

→ Fibres: Yarn is made up of very small strands called fibres.

→ Jute: Jute is strong and rough, the necktie is smooth and shiny as it is made up of silk.

→ Plant Fibres: The Fibres obtained from plants are called plant fibres.
For example cotton, jute, coir.

→ Animal fibres: The fibres obtained from animals are called animal fibres.
For example wool, silk.

→ Synthetic Fibres: Fibres prepared by a man using chemicals and other materials are called synthetic fibres.

→ Ginning: The separation of cotton from its seeds by steel combs is called ginning.

→ Sericulture: The rearing of silkworms to produce silk.

→ Retting: Formation of jute fibre from the stem of the jute plant by the process of retting.

→ Shearing: Removing wool from sheep using clippers.

→ Spinning: The process of making yarn from fibres is called spinning.

→ Weaving and Knitting: The process of arranging two sets of yarn together to make a fabric is called weaving.

→ In contrast, a single yarn is used to make a piece of fabric in knitting.

This PSEB 6th Class Science Notes Chapter 2 Components of Food will help you in revision during exams.

PSEB 6th Class Science Notes Chapter 2 Components of Food

→ Nutrients are the substances that are needed for the proper growth and development of the body.

→ Carbohydrates, proteins, fats, minerals, and vitamins are the main nutrients in our food.

→ In addition to these, our body needs water and roughage.

→ Carbohydrates are made up of carbon, hydrogen, and oxygen. These are instant sources of energy and are called energy-giving food.

→ Bajra, jowar, rice, wheat, jaggery, mango, banana, and potato are the main sources of carbohydrates.

→ We have two types of carbohydrates. These are simple carbohydrates and complex hydrates.

→ Examples of simple carbohydrates are glucose, fructose, sucrose, lactose, etc.

→ Examples of complex carbohydrates are starch, cellulose, glycogen, etc.

→ Carbohydrates sweet in taste are called sugars.

→ Sucrose is known as table sugar.

→ Fructose is called fruit sugar.

→ Lactose is called milk sugar.

→ Starch is tasteless and insoluble in water. It is made up of many glucose units.

→ The main sources of starch are potatoes, wheat, rice, maize, etc.

→ During digestion, starch is first converted into glucose and finally into carbon dioxide and water. So, starch is not an instant source of energy.

→ Starch detection can be done by an iodine test. It gives a blue-black colour with iodine.

→ Proteins are made up of carbon, hydrogen, oxygen, and nitrogen. They are called body-building foods.

→ The growth and repair of body cells is the main function of proteins. These also protect us from many diseases.

→ Plants and animals both are sources of proteins.

→ Proteins from plants are called plant proteins and proteins from animals are called animal proteins.

→ Beans like soybeans, peas, and pulses like gram and moon are sources of plant proteins.

→ We also get proteins from spinach, mushroom, broccoli, etc.

→ Mean, fish, poultry, milk, and milk products are the main sources of proteins.

→ Some proteins speed up various reactions occurring in our bodies. These are known as enzymes.

→ Enzymes are proteins that speed up various activities inside the body of a living organism.

→ Proteins when added to a solution of copper sulphate and caustic soda gives blue colour. This reaction is used for detecting the proteins.

→ Fats also give us energy. They give larger amounts of energy in comparison to carbohydrates. They do not release energy instantly.

→ Fats are known as the richest source of energy. Carbohydrates are known as instant sources of energy.

→ Important plant sources of fats are vegetable oils like mustard oil, coconut oil, and sunflower oil.

→ Other sources of fats are cashew, almonds, groundnut, and sesame seeds.

→ Important animal sources of fat are meat, eggs, fish, milk, and milk products like butter, ghee, etc.

→ Fats give energy, prevent heat loss from the body.

→ The presence of an oily patch on paper confirms the presence of fat in any food item.

→ Our bodies also need minerals. Calcium, iron, iodine, and phosphorus are important minerals. These do not give us energy.

→ Iron is needed for the formation of haemoglobin and calcium is needed for forming bones.

→ Phosphorus provides strength to bones and teeth.

→ Iodine is needed for the normal functioning of the thyroid gland.

→ Vitamins are essential for the proper functioning of our body.

→ We have different vitamins like A, B, C, D, E, and K.

→ Sources of vitamin A are eggs, meat, milk, cheese, green leafy vegetables, carrot, papaya, etc. It is needed for healthy eyes and skin.

→ Sources of vitamin B are milk, green vegetables, peas, eggs, cereals, mushrooms, etc. It is needed for normal growth and proper functioning of the central nervous system and digestive system.

→ Sources of vitamin C are citrus fruits (lemon, orange, etc.), amla, tomato, broccoli, etc. It is needed for fighting against diseases.

→ Sources of vitamin D are dairy products, fish liver oil, exposure to sunlight, etc. It is needed for healthy bones and teeth.

→ Sources of vitamin E are almonds, peanuts, sunflower oil, soyabean oil, leafy vegetables. It is needed for protecting cells from damage and helping our body to lower different problems.

→ Sources of vitamin K are green leafy vegetables, fish meat, eggs, cereals, etc. It is needed for the clotting of blood.

→ Nutrients: are the substances that are needed for the proper growth and development of the body.

→ Balance diet: The diet that contains an adequate amount of all the essential nutrients, roughage, and water for proper growth and development of the body is called a Balanced diet

→ Deficiency Diseases: The disease which is caused due to shortage of nutrients in our diet for a long time is called deficiency disease.

→ Goiter: A deficiency disease caused due to deficiency of iodine and its main symptom is an enlargement of the gland in the neck.

→ Scurvy: It is a disease caused by deficiency of vitamin C and its main symptoms include bleeding gums.

→ Beri-Beri: It is a disease caused by a deficiency of vitamin-B.

→ Rickets: It is a disease caused by deficiency of vitamin D and its main symptoms include softening and bending of bones.

→ Anaemia: It is a disease caused by deficiency of iron and its main symptoms include weakness, fatigue, and pale skin.

→ Roughage: The fibrous indigestible material present in food is termed roughage.

This PSEB 6th Class Science Notes Chapter 1 Food Where Does it Come From will help you in revision during exams.

PSEB 6th Class Science Notes Chapter 1 Food Where Does it Come From

→ All living beings need the energy to carry out their daily activities.

→ Food is needed by living beings for their growth, getting energy for doing work, replacement and repair of their damaged body parts, and protection against diseases.

→ Different varieties of food like fruits, vegetables, milk products, sweets, eggs, meat, chapati, and bakery products are present in nature.

→ The materials needed to prepare food items are called ingredients. Food materials can be made of one or two or many ingredients.

→ Plants are the chief source of food for us and other animals. However, few food materials are also obtained from animals.

→ Green plants can prepare their own food by using sunlight, carbon dioxide, and water to prepare their food. This process is called photosynthesis.

→ Every part of a plant where the food is stored is edible i.e. seed, flower, stem, root, leaf.

→ The plant parts which are used by us as food are called edible parts.

→ We eat roots of carrot, radish, turnip, sweet potato, etc. We also use stems of certain plants.

→ Some stems like those of ginger, potato, onion, turmeric grow underground and store food.

→ Stems of ginger and turmeric are used as spices.

→ The stem of sugarcane is used to make juice, sugar, and jaggery.

→ We eat different types of fruits like apple, mango, guava, papaya, orange, etc.

→ All these fruits are eaten raw i.e. without cooking. We make jams and pickles from some fruits.

→ Fruits are essential for good health as these are important sources of vitamins and minerals.

→ We use leaves of various plants like mustard, spinach, cabbage, coriander, mint, etc.

→ We use seeds of many plants as food like wheat, rice, maize, gram, peas, kidney beans and green gram (moong), etc.

→ Seeds of some crops like gram, peas, kidney beans, and green gram (moong) are known as pulses whereas seeds of wheat, rice, and maize are known as cereals.

→ We get milk, honey, meat, eggs, oil, etc. from animals.

→ Honey contains sugar, water, minerals, enzymes, and vitamins. Nectar of flowers is a source of honey.

→ On the basis of the food taken by animals, there are three categories of the animals:

• Herbivores
• Carnivores
• Omnivores

→ Herbivores are the animals that eat only plants and plant products are called herbivores, e.g. cows, goats, rabbits, sheep, deer, elephants, etc.

→ Carnivores are the animals which eat other animals are called carnivores, e.g. lions, tigers, lizards, snakes, etc.

→ Omnivores are the animals which eat both plants and animals are called omnivores. e.g. Crow, bear, dog, and rat, man, etc.

→ Milk contains proteins, sugar, fats, and vitamins.

→ It is used worldwide as food that can be converted into dairy products like cheese, butter, curd, cream, etc.

→ People eat the meat of goats, sheep, chicken, fish, and sea animals like prawns, crab.

→ Meat is also used as food and it contains a great number of proteins and fats.

→ People eat eggs of hen and duck and other birds.

→ The white part of the egg is called albumen and the yellow part of the egg is called yolk.

→ Albumen is rich in proteins and you are rich in fats.

→ Food: Substances providing energy to do work, maintain body heat, protect us from diseases, etc. is called food.

→ Balance diet: A diet that contains all the nutrients needed by the body is called a balanced diet.

→ Edible: The substances/materials which are safe for eating are called edible substances.

→ Ingredients: Materials needed to prepare food Items.

→ Pulses: Seeds of some crops like gram, peas, moong.

→ Cereals: Seeds of grass crops e.g. wheat, rice, maize

→ Albumin: White part of the egg.

→ Yolk: Yellow part of the egg

→ Nectar: Sugary fluid present in flowers

→ Herbivores: Plant-eating animals are called herbivores.

→ Nectar: Sugary fluid present in flowers

→ Autotrophs: Organisms that can prepare their own food by photosynthesis.

→ Heterotrophs: Organisms that depend on other organisms for food

→ Herbivores: Organisms that eat only plants and plant products

→ Carnivores: Animals eating other animals are called carnivores.

→ Omnivores: Animals that eat both plants and animals are called omnivores.

This PSEB 7th Class Science Notes Chapter 18 Wastewater Story will help you in revision during exams.

PSEB 7th Class Science Notes Chapter 18 Wastewater Story

→ Sewage is liquid waste, most of it is water that has dissolved and suspended impurities. These impurities are called contaminants.

→ An underground network of pipes that carry wastewater from a home to a point of disposal is called Sewerage.

→ Sewage is transported through the closed pipes to the wastewater treatment plants where pollutants are separated and reformed and then flow into rivers and oceans.

→ During wastewater treatment pollutants are separated by physical, chemical, and biological methods.

→ Sludge is a solid that settles to the bottom during water purification.

→ Wastewater treatment co-products are sludge and biogas.

→ A manhole is a lid-covered open space through which a person can enter and can check the sewerage system.

→ Open defecation is a breeding ground for flies, mosquitoes, and other insects that cause many diseases.

→ Do not throw oil, ghee, grease, etc. in a drain or in the open. Doing so will make drain chock.

→ Throw trash only in the bin (dustbin).

→ Pollutants: Dissolved and suspended impurities in dirty water are called pollutants.

→ Sewerage: A network of small and large pipes that carry wastewater to the drainage area.

→ Manhole: Large open mouth holes are made at every 50-60 meters of the sewerage system.

→ Individual who enters the sewage can check and remove sewage problem if any.

→ Water Treatment Plant: A place where impurities are separated from wastewater.

→ Water Treatment: The process of separating impurities from wastewater is called water treatment.

→ Sludge is the solid that settles in the sewage water purification tank.

→ Septic tank: This is a small system of sewage treatment containing monoaerobic bacteria that remove waste products. It has connections with main sewage pipes.

This PSEB 7th Class Science Notes Chapter 17 Forests: Our Lifeline will help you in revision during exams.

PSEB 7th Class Science Notes Chapter 17 Forests: Our Lifeline

→ A system made up of plants, animals, and micro-organisms are called a forest.

→ The top layer of the forest is Canopy Layer, the mid-layer is the Crown layer and the lower layer is the Understory layer.

→ Forests protect the soil from erosion.

→ Soil helps in the growth and development of trees.

→ Humus shows that nutrients from the bodies of dead plants and animals have been incorporated into the soil.

→ Forests act like green lungs and produce many products. That is why forests are so important.

→ A forest is an area whose uppermost layer is topped by trees.

→ Forests are always green.

→ A variety of animals, plants, and insects are found in forests.

→ All wild animals, herbivores or carnivores, depend on plants for food in one or the another way.

→ Forests continue to grow and develop and can regenerate.

→ Forests affect climate, water cycle, and air quality.

→ Trees, shrubs, vegetation, herbs, etc. all are found in forests.

→ According to the height of trees and plants, forests are divided into three categories:

• Canopy
• Crown
• Understory

→ Forest soil helps in regeneration.

→ Forest plants emit vapours and help bring rain and regulate the temperature of the environment.

→ Different layers of vegetation in forests provide food and shelter to animals, birds, and insects.

→ In the forest, soil, water, air, and living things have interdependence on each other.

→ Forests provide important basic necessities for communities living in forested areas.

→ Forests maintain and regulate climate, water cycle, and air quality.

→ Decomposers depend on the dead bodies of plants and animals and turn them into simple substances.

→ Deforestation causes global warming, decreases rainfall, increases pollution, and erodes soil.

→ To maintain balance in nature and maintain habitat for wild animals and plants forest plays an important role.

→ Forest: A forest is an area where there is a lot of dense vegetation, including animals, trees, bushes, and weeds that grow naturally.

→ Canopy: The top layer of tree branches forms a dense top layer of trees on earth which is called the canopy.

→ Crown layer: The layer in which the branches and trunks of trees come, is called the crown or crown layer.

→ Understory Layer: The shaded area below which there is very little light, is called the lower or understory layer.

→ Ecosystems: Living things and their environment work together to create ecosystems. Plants, animals, and microorganisms are the biological components of the ecosystem. These are divided into different categories of producers, consumers, and decomposers.

→ Food chain: In ecology, the sequence of transfer of matter and energy in the form of food from one organism to another organism is called a food chain.
For example:

→ Food Web: A food web consists of a network of many food chains. A food chain helps provide food to organisms at the next food level.

→ Afforestation: The process of planting trees on a large scale is called Afforestation.

→ Decomposers: Microorganisms that decompose the dead bodies of plants and animals into humus, are called Decomposers.

→ Erosion: In the absence of trees and plants top layer of soil is lost, This process of carrying away the topsoil by wind and water is called soil erosion.

→ Replenishment of forest: Planting a large number of plants and trees in the forest area is called forest replenishment.

This PSEB 7th Class Science Notes Chapter 16 Water: A Precious Resource will help you in revision during exams.

PSEB 7th Class Science Notes Chapter 16 Water: A Precious Resource

→ All living things need water to survive.

→ The three states of water are solid, liquid and gas.

→ Less than 1% of the world’s water is freshwater or out of all Earth’s water, only about 0.00367% is available for human consumption.

→ Our future depends on the availability of water.

→ Every year March 22 is celebrated as World Water Day.

→ The minimum recommended amount of water per person is 50 Litres per day.

→ Water scarcity has become a global concern.

→ About 71% of the earth’s surface is covered by water.

→ Almost all the water on the earth is found in the oceans, seas, rivers, land, and atmosphere.

→ Useful water is freshwater.

→ Salt-free water present on Earth is 0.006% of the total amount of water available on Earth.

→ In solid-state water is present as ice and snow found in the snow-covered mountains at the poles of the earth and as glaciers.

→ Water in the liquid state is found in oceans, lakes, rivers as well as groundwater below ground level.

→ In the gas state, water is present in the air in the form of Vapours in the atmosphere.

→ Rainwater is considered to be the purest form of water.

→ The transfer of water is done by the water cycle.

→ The main source of water is groundwater.

→ Groundwater accumulates in the layers of stable hard rocks.

→ Population growth, increase in industrial and agricultural activities, etc. affect the groundwater level.

→ Groundwater level decreases due to high utilization of groundwater and low absorption of water by land.

→ Rainwater is used for rainwater harvesting.

→ Factors affecting groundwater levels are deforestation and excessive water absorption.

→ Bawris and Drip irrigation systems are some of the techniques that can be used to meet water scarcity.

→ Without water, greenery will disappear from the earth, which means the end of life.

→ Time demands that everyone should use water sparingly. Hence the unwanted and excessive use of groundwater should be avoided.

→ When plants are not watered for a few days, they wither away and eventually die.

→ The Punjab Government had passed the Water Conservation Act 2009 of Punjab in the year 2009 under which the date of transplantation of Paddy crop for the first time was fixed on 10th June. This was later changed to June 15, 2015.

→ The Dead Sea is a salty lake bounded on the east by Jordan and on the west by Israel and Palestine.

→ It is 8.6 times saltier than the other oceans having more alkalinity, the cause non-existence of plants and living creatures, which is why it is called the Dead Sea.

→ Water Cycle: Many processes such as evaporation of water into the air, formation of clouds through condensation, and the occurrence of precipitation which maintains water on the earth, even though the whole world uses it is called the water cycle.

→ Fresh Water: The water that is suitable for drinking is freshwater. It contains a very small amount of salt. This is about 3% of the total water on earth, which is found in rivers, lakes, glaciers, snow-capped peaks, and underground.

→ Water table: At a depth near the water source where the space between the rocks is filled with water is called groundwater area or saturated area. The surface of this water is called the water table.

→ Wet Rock layer: Groundwater between layers of hard rock below the water table is called the wet rock layer. This water is drained through tube wells.

→ Infiltration: Water from various sources such as rain, rivers, and ponds is going even deep inside the earth due to gravity. This is called infiltration.

→ Water management: The efficient distribution of water is called water management.

→ Drip Irrigation System: This is an irrigation technique in which water is dripped through pipes to the plant.

→ Water Storage: The process of collecting rainwater and using it when needed is called water storage. This is done to compensate for the water level.

→ Bawris: This is the ancient method of water storage. This method is still practiced in many parts of India today.

This PSEB 7th Class Science Notes Chapter 15 Light will help you in revision during exams.

PSEB 7th Class Science Notes Chapter 15 Light

→ A ray coming from a source of light falls on the object and after reflection enters our eyes so that we see the objects.

→ Light always travels in a straight line.

→ The reflection from the surface of the object must be the same to see the image.

→ After hitting a surface, the light returns to the same medium in a certain direction. The process of coming back of the light is called reflection of light.

→ The ray of light that strikes an object is called an incidental ray and the ray of light which after hitting an object returns to the same medium in a particular direction it is called a reflected ray.

→ The angle between the incident ray and the perpendicular drawn at the point of incidence is called the Angle of Incidence.

→ The angle between the reflected ray and the perpendicular drawn at the point of reflection is called the angle of reflection.

→ The angle of incidence and the angle of reflection are always equal. This is called the law of reflection.

→ The image formed on the screen is called a Real image.

→ The image that cannot be obtained on the screen even if the reflected rays appear to meet is called a Virtual image.

→ The image formed by a plane mirror is always formed behind the mirror. This image is virtual is erect and of the same size as that of the object.

→ The image formed by a plane mirror is at the same distance behind the mirror as the object is placed in front of the mirror.

→ The image formed by a plane mirror is laterally inverted i.e. the left side of the object becomes to the right of the image and the right side of the object is seen to be left of the image.

→ A concave mirror is a spherical mirror with a reflecting surface facing inwards.

→ A convex mirror is a spherical mirror with a reflecting surface facing outwards.

→ The rays of light coming from a distant object are considered to be parallel to each other and the point at which they actually meet after being reflected from the mirror or appear to meet is called the focal point of the mirror.

→ For a concave mirror, a virtual, erect, and large image is formed only when the object is placed between the principal focus and the mirror.

→ For a convex mirror, the image formed is erect, virtual, and smaller in size than the size of the object.

→ The lens is a piece of transparent medium surrounded by two surfaces. The two main types of lenses are

• Convex lens
• Concave lens

→ The convex lens is thicker in the middle and thinner at the edges.

→ The concave lens is thin in the middle than at the edges.

→ A convex lens is also called a Convergent lens whereas a Concave lens is called a Divergent lens.

→ The convex lens can be used to see small objects. Hence it is also called magnifying glass or reading glass.

→ On allowing white light to pass through a prism, it splits up into seven colours, which means white light is composed of seven colours.

→ The point at which the rays of light coming from a distant object (such as the sun) meet or appear to meet after suffering refraction from the lens is called the focal point of the lens.

→ When a ray of light enters from one medium to another transparent medium, it changes its path. The phenomenon of light changing its path is called the refraction of light.

→ Reflection of light: When light travelling in a straight line strikes the surface of a mirror or a polished opaque surface, it changes its direction and returns to the same medium. The process of coming back from the light is called the reflection of light.

→ Incidental ray: A ray of light falling on the smooth and polished surface is called an incident ray.

→ Reflected Ray: A ray of light after striking a mirror changes its direction and returns to the same medium, which is called a reflected ray.

→ The angle of incidence: The angle between the incident ray and the perpendicular drawn at the point of incidence is called the angle of incidence.

→ The angle of reflection: The angle formed between the reflected ray and the perpendicular drew at the point of incidence is called the angle of reflection.

→ Point of incidence: The point at which the incident ray strikes the surface of the mirror, is called the point of incidence.

→ Perpendicular: The normal or perpendicular line drawn from point of incidence.

→ Real Image: When the light coming from an object after reflection meets at a point forming an image then such image is called a real image.

→ Virtual reflection: When the rays of light only appear to meet at a point after reflection from a mirror then that point is called a virtual image. A virtual image cannot be obtained on the screen.

→ Spherical Mirror: A mirror whose reflecting surface is a part of a hollow spherical surface.

→ Concave mirror: If the inner surface of a spherical mirror is reflecting, it is called a concave mirror.

→ Convex mirror: If the outer surface of the spherical mirror is reflecting, it is called a convex mirror.

→ Light Reflection: The bouncing back of light after when light strikes a smooth surface.

→ Refraction of Light: When a ray of light enters from one transparent medium to another transparent medium, the ray of light changes its path. The phenomenon of change of path by light is called refraction.

→ Convex lens: This is a piece of transparent shell that is thicker in the middle than the edges. It is also called a converging lens.

→ Concave lens: This is a piece of the transparent medium that is thin in the middle and thick at the edges. This lens is also called a diverging lens.

→ Focus: The point on the principal axis where the parallel rays of light meet or appear to meet after passing through the lens is called the focus.

→ Focal length: The distance between the principal focus and the center of the lens is called the focal length of the lens.

→ Splitting of light: The process of splitting by when white light passes through a transparent medium (such as a prism of glass) of white light into seven colours is called the splitting of light.

→ Spectrum: It is a band of seven colours obtained after passing white light through the prism. These colors from top to bottom are Violet, Indigo, Blue, Green, Yellow, Orange, and Red.

This PSEB 7th Class Science Notes Chapter 14 Electric Current and Its Effects will help you in revision during exams.

PSEB 7th Class Science Notes Chapter 14 Electric Current and Its Effects

→ Electrical components can be represented by symbols that are very convenient in representation.

→ The circuit diagram is a diagrammatic representation of an electrical circuit.

→ The symbol of an electric cell is two parallel lines, one of which is a long line and the other a short line.

→ A battery is a combination of two or more cells.

→ Batteries are used in flashlights, transistors, radios, toys, TVs, remote controls, etc.

→ Electric bulbs have a thin filament, which illuminates by the flow of electric current. This is due to the heating effect of the electric current.

→ In electric heaters, room heaters, and testers heating effect of current is used.

→ An electric fuse consists of a special wire having a low melting point so that when it is placed in an electric circuit carrying heavy current it melts.

→ Electrical fuses are used in an electric circuit to save electrical appliances from fire or any other damage when heavy current flows in the circuit.

→ Any metallic wire acts as a magnet when an electric current passes through it. This effect of electric current is called its magnetic effect.

→ When current is passed through an iron bar placed in a coil, it acts like a magnet. A magnet made in this way is called an electric magnet.

→ An electromagnet is a magnet and when an electric current is switched off, it loses its magnetic properties.

→ Electromagnets are used in many devices, such as electric bells and magnetic cranes, etc.

→ Conductor: A substance that allows an electric current to pass through it, is called a conductor.

→ Resistance: A substance that opposes the flow of electric current from passing through it, is called resistance.

→ Switch: This is a simple device that is used to complete the path for the flow of current or to break it, is called a switch.

→ Circuit: The path which electric current follows from the positive terminal of cell/battery to its negative terminal via bulb, resistance, and switch.

→ Bulb: A simple device that converts electrical energy into light energy.

→ Filament: A thin wire of tungsten metal that gets heated due to the passage of electric current and emits light, is called Filament.

→ Battery: This is a combination of two or more electrochemical cell that converts their chemical energy into electrical energy.

→ Electromagnetism: Place a soft piece of iron inside the coil and pass an electric current through the coil. With this comes the property of a magnet inside a piece of iron. This technique is called electromagnetism.

→ Electric bell: A mechanical device that works on the principle of an electromagnet and produces repeated sounds on passing electric current.

→ Electric Crane: It consists of a crane with a large powerful magnet attached to one end that is used to lift, heavy objects made of iron and move them from one place to another place.