CLASS: IX NCERT (CBSE)
Chemistry: For Class 9
Matter in Our Surroundings
Matter is any substance that has mass and occupies space. Matter is made up of small particles.
Solids have definite shapes and volumes. Liquids do not have definite shapes.
Liquids do have definite volumes.
Gases do not have definite shapes or volumes.
Solids cannot be compressed, except porous solids.
Liquids take the shape of the container and have definite volume.
Gases have no definite shape and volume.
Melting is the process where solid changes into a liquid.
Heat energy that is used up by a body to change its state or phase is called latent heat.
Latent Heat of Fusion: The amount of heat energy that is required to change unit mass of a solid into liquid at a standard atmospheric pressure.
Vaporisation: The process where a liquid changes to gas.
Latent Heat of Vaporisation: The amount of heat required to change a unit mass of liquid to gas at standard atmospheric pressure.
Evaporation The process where a liquid changes into vapour at any temperature below its boiling point. Surface area, temperature and the wind are the factors that affect the rate of evaporation.
The process where vapour changes to a liquid is called condensation.
The process, where a liquid converts into a solid, is called freezing.
The process, where a solid, on heating, directly changes into gas without changing into liquid, and a gas, on cooling, directly changes to solid without changing into liquid is called sublimation. Applying pressure and reducing temperature can liquefy gases.
The phenomenon of the change of matter from one state to another and back to original state, by altering the temperature is called interconversion of states of matter.