For any substance, why does the temperature remain constant during the change of state.?
The temperature remains constant during the change of state because the energy is required for the substance to undergo a change from one form to another form, i.e Heat absorbed is utilised in breaking of bonds and several other restructural processes to occur. This heat is known as latent heat.
There are various types of latent heats :
1) Latent Heat of fusion: Heat absorbed when a solid is converted to liquid.
It is the heat required to change 1 kg of a solid substance into liquid state at the melting point of the substance. For example, amount of heat required to melt ice at 0 ° C into water at 0 °C, will be known as the Latent Heat of Fusion of ice.
2)Latent Heat of Vaporisation :​Heat absorbed when a liquid is converted to vapour.
It is the heat required to change 1 kg of a liquid substance into gaseous state at atmospheric pressure, at the boiling point of the substance. For example, amount of heat required to vaporize water at 100 ° C into the vapor state at 100 ° C, atmospheric pressure, will be known as the Latent Heat of Vaporization of water.
3)Latent Heat of Sublimation : Heat absorbed when a solid is converted to vapour directly.
It is the heat required to change a unit mass of solid substance into gaseous state at atmospheric pressure, without any change in temperature of the substance. For example, the heat required to sublimate solid camphor into its vapors at atmospheric pressure and constant temperature, will be known as the Latent heat of Sublimation of Camphor
There are various types of latent heats :
1) Latent Heat of fusion: Heat absorbed when a solid is converted to liquid.
It is the heat required to change 1 kg of a solid substance into liquid state at the melting point of the substance. For example, amount of heat required to melt ice at 0 ° C into water at 0 °C, will be known as the Latent Heat of Fusion of ice.
2)Latent Heat of Vaporisation :​Heat absorbed when a liquid is converted to vapour.
It is the heat required to change 1 kg of a liquid substance into gaseous state at atmospheric pressure, at the boiling point of the substance. For example, amount of heat required to vaporize water at 100 ° C into the vapor state at 100 ° C, atmospheric pressure, will be known as the Latent Heat of Vaporization of water.
3)Latent Heat of Sublimation : Heat absorbed when a solid is converted to vapour directly.
It is the heat required to change a unit mass of solid substance into gaseous state at atmospheric pressure, without any change in temperature of the substance. For example, the heat required to sublimate solid camphor into its vapors at atmospheric pressure and constant temperature, will be known as the Latent heat of Sublimation of Camphor