What is Latent heat of vaporisation?

The latent heat of vaporization is the amount of heat energy required to convert a unit mass or unit mole of a substance from liquid phase to gas phase at constant temperature and pressure. In simpler terms, it is the heat energy absorbed by a substance during the phase change from liquid to gas, without a change in temperature.

During the phase transition from liquid to gas, the substance absorbs energy to overcome the attractive forces between molecules (such as hydrogen bonds, van der Waals forces, etc.) holding the liquid together. This energy is used to break these bonds and allow the substance to change phase into a gas.

The latent heat of vaporization is typically expressed in units of joules per kilogram (J/kg) in the SI system, or in units of calories per gram (cal/g) in the CGS system. For example, the latent heat of vaporization of water at 100°C is approximately 2260 kJ/kg (or 540 cal/g).

Key points about latent heat of vaporization:
– It is specific to each substance and depends on the substance’s molecular structure and intermolecular forces.
– It is a measure of the amount of energy required to change the phase of a substance from liquid to gas.
– It is an intensive property, meaning it does not depend on the amount or size of the substance being vaporized, but rather on the substance itself.

In summary, latent heat of vaporization is the energy absorbed by a substance during the phase change from liquid to gas, maintaining a constant temperature and pressure.