Latent heat refers to the heat energy absorbed or released by a substance during a phase change without a change in temperature. It is the energy required to change the state of a substance from one phase to another, such as from solid to liquid or from liquid to gas.
The latent heat of fusion is the amount of heat energy required to change a substance from a solid phase to a liquid phase at its melting point, while maintaining a constant temperature. During this phase change, the substance absorbs heat energy from its surroundings to break the intermolecular bonds holding its particles together. The latent heat of fusion is typically expressed in joules per gram (J/g) or calories per gram (cal/g).
The latent heat of vaporization, on the other hand, is the amount of heat energy required to change a substance from a liquid phase to a gaseous phase at its boiling point, while again maintaining a constant temperature. This process involves the breaking of intermolecular bonds and the conversion of liquid particles into gas. The latent heat of vaporization is also usually given in joules per gram (J/g) or calories per gram (cal/g).
Both the latent heat of fusion and the latent heat of vaporization are specific to each substance and are indicative of the strength of the intermolecular forces within that substance. These latent heats represent the energy required to overcome those forces and facilitate the phase change.