Matter can change from form to other form i.e from solids to liquids to gases. The phenomenon of the change of matter from one state to another and back to original state, by altering the temperature. Example: melting of ice into water.
Inter-conversions: effect of temperature:
When heat energy is supplied to the particles they starts moving. The energy supplied to the particles is used to overcome the forces of attraction. This results in the particles to leave their position and start moving more freely.
Melting is the process where solid changes into a liquid.
The temperature at which a solid melts to become a liquid at the atmospheric pressure is called its melting point.
The word 'latent' means hidden. The characteristic amount of energy absorbed or released by a substance during a change in its physical state that occurs without changing its temperature is known as latent heat.
Latent heat of fusion :
Latent heat of fusion is the amount of heat energy required to change 1 kg of a solid into liquid at atmospheric pressure at its melting point.
The temperature at which a liquid starts boiling at the atmospheric pressure is known as its boiling point.
Latent heat of vaporization:
Latent heat of vaporization is the amount of heat energy required to change 1 kg of liquid into a gas at atmospheric pressure at the boiling point.
The process where a liquid changes into vapor at any temperature below its boiling point is evaporation .
Factors affecting evaporation:
- Surface area,
- Humidity and
- Wind speed.
The process where vapor 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
Example: solid ammonium chloride, on heating directly converts into vapors without changing to the liquid state. These vapors get condensed to the solid state by condensation process.
A gas is liquefied by applying high pressure and reducing the temperature. Example: petroleum gas is liquefied by applying high pressure and reducing the temperature to liquefied petroleum gas(LPG).