## Latent Heat

### Definition :

Latent heat refers to the energy absorbed or released by a substance during a phase change, occurring without a temperature change.

• The heat of fusion (Lf) is the energy required to melt a solid or freeze a liquid.

• The heat of vaporization (Lv) is the energy needed to vaporize a liquid or solid or condense a vapor.

Latent heat is typically measured in terms of energy per mole or unit mass of the substance undergoing a phase change. Common units include:

• Joules per mole (J/mol) or calories per mole (Cal/mol).

• Joules per kilogram (J/kg) or calories per kilogram (Cal/kg).

Q = nL Q=nL

Or

Q = mL Q=mL