Latent heat is the quantity of heat absorbed or released by a substance undergoing a change of state, such as ice changing to water or water to steam, at constant temperature and pressure.
Types:
There are three phases of the substance: solid, liquid and gaseous. Accordingly there are three types of latent heats, which have been described below:
1) Latent heat of fusion: Amount of heat required to melt the substance of unit mass from solid to liquid or the amount of heat required to be removed from the unit mass of substance to freeze it from liquid to solid is called as latent heat of fusion.
2) Latent heat of vaporization: The amount of heat required by the unit mass of substance to vaporize from liquid to gaseous state or the amount of heat required to be removed from the unit mass of substance to condense from the gaseous to liquid phase is called as latent of vaporization.
3) Latent heat of sublimation: The amount of heat required by the unit mass of substance to convert directly from solid to gaseous phase or the amount of heat required to be removed from the gaseous substance to change it to the solid phase is called as latent heat of sublimation.