This PSEB 9th Class Science Notes Chapter 1 Matter in Our Surroundings will help you in revision during exams.
PSEB 9th Class Science Notes Chapter 1 Matter in Our Surroundings
→ Matter: It is anything that occupies space, has mass, and can be judged by any one or more of the known five physical senses.
→ Early Indian philosophers classified matter into five basic elements called Panch Tatva. These are air, earth, fire, sky, and water.
→ Modern-day scientists have classified matter on the basis of its physical properties and chemical nature.
→ The matter is made up of extremely small particles and there are vacant spaces in them.
→ Particles of matter are always in motion and have kinetic energy.
→ The speed of particles increases with the increase in temperature.
→ The mixing up of particles of different substances is called diffusion.
→ All matter is made up of a large number of extremely small particles called molecules.
→ The material represents a particular kind of matter.
→ Material can be homogeneous or heterogeneous.
→ Homogeneous material is a material that has a uniform composition throughout. It consists of a single phase.
→ Heterogeneous material is a material that does not have a uniform composition throughout. It consists of two or more phases.
→ The substance is a homogeneous material that is made up of only one kind of atom or material. (Substance always refers to pure substance).
→ Based upon its physical state, there are three states of matter, i.e. solid, liquid, and gas.
→ There are two new states of matter. These are plasma and Bose-Einstein condensate.
→ Solid: It is that state of matter which has a definite mass, volume, and shape.
→ Liquid: It is that state of matter which has a definite mass and volume but has no definite shape.
→ Gas: It is that state of matter which has a definite mass but has neither definite shape nor definite volume.
→ The forces of attraction between the particles are maximum in solids, intermediate in liquids, and maximum in gases.
→ The vacant spaces between the constituent particles and kinetic energy of particles are minimum in the case of solids, intermediate in liquids, and maximum in gases.
→ The arrangement of constituent particles is most ordered in the case of solids, in the case of liquids the layers can slip over each other while in the case of gases, there is no order, particles can move randomly.
→ The different states of matter are interconverted by changing temperature or pressure or both.
→ Melting point is the temperature at which solid changes into a liquid state.
→ The boiling point is the temperature at which a liquid changes into vapour under atmospheric pressure. At boiling point, vapour pressure of the liquid is equal to atmospheric pressure.
→ Boiling is a bulk phenomenon as it involves the whole of the liquid.
→ The rate of evaporation depends upon the surface area, temperature, humidity, and wind speed.
→ The slow passing out of molecules of a liquid into a gaseous state at a temperature below its boiling point is called evaporation.
→ Evaporation causes cooling. It is a surface phenomenon.
→ Boiling is a fast process whereas evaporation is a slow process.
→ Sublimation is the process due to which a solid directly changes into the gaseous state on heating and a gaseous state directly changes into a solid-state on cooling without changing into the liquid state.
→ Vapour is a substance that exists in the gaseous state at a temperature lower than the boiling point of its liquid state.
→ Temperature on Kelvin scale = 273 + Temperature on centigrade scale. (T K = 273 + t°C) Water freezes at 0°C or 273 K.
→ Water boils at 100°C or 373 K.
→ Units of Latent heat of fusion are kJ/kg or kcal/kg
→ Units of Latent heat of vaporisation are kJ/kg or kcal/kg
→ \(\frac{F-32}{9}=\frac{C}{5}\)
F = Temperature on Fahrenhiet scale.
C = Temperature on Centigrade scale.
Some measurable quantities and their units are:
| Quantity | Unit | Symbol |
| Temperature | kelvin | K |
| Length | metre | m |
| Mass | kilogram | kg |
| Weight | newton | N |
| Volume | cubic metre | m3 |
| Density | kilogram per cubic metre | Kg m-3 |
| Pressure | pascal | Pa |
→ Matter: It is anything that occupies space, has mass, and can be judged by any one or more of the known five physical senses.
→ Panch Tatva: Indian philosophers classified matter into our basic elements called Panch Tatva. These are air, earth, fire, sky, and water.
→ Diffusion: It is the property of the mixing of particles of two or more substances.
→ Solid: It is that state of matter which has a definite mass, volume, and shape.
→ Liquid: It is that state of matter which has a definite mass and volume but has no definite shape.
→ Gas: It is that state of matter which has a definite mass but has neither definite shape nor definite volume.
→ Density: It is the mass per unit volume of a substance.
→ Melting point: It is the temperature at which solid changes into the liquid state.
→ Fusion: It is the process of conversion of a solid into a liquid.
→ Solidification or freezing: It is the process of conversion of a liquid into a solid.
→ Sublimation: It is the process due to which a solid directly changes into the gaseous state on heating and a gaseous state directly changes into the solid state on cooling without changing into a liquid state.
→ Latent heat of fusion is the amount of heat energy required to change 1 kg of solid into liquid at its melting point.
→ Latent heat of vaporisation is the amount of heat energy required to change 1 kg of a liquid to gas at atmospheric pressure and at its boiling point.
→ Boiling is a bulk phenomenon as it involves the whole of the liquid.
→ Boiling point: It is the temperature at which a liquid changes into vapour under atmospheric pressure.
→ Evaporation: The slow passing out of molecules of a liquid into a gaseous state at a temperature below its boiling point.
→ Dry Ice: Solid carbon dioxide is called dry ice.
→ Freezing point: It is the temperature at which a liquid substance changes into a solid substance.
→ Liquified Petroleum Gas (LPG): When butane is subjected to the action of high pressure, it is liquid to give LPG which is used as a fuel.
→ Compressed Natural Gas (CNG): When natural gas is subjected to the action of high pressure it gets liquified to give CNG which is used as a fuel for automobiles.
→ Vapour: It is a substance that exists in the gaseous state at a temperature lower than the boiling point of its liquid state.