Entropy Change in Phase Transitions

When a solid melts and produces liquid, the process occurs at the melting point of the solid. For example, ice melts at 273 K and produces water at the same temperature.

H2O (s) → H2O (l)

The heat involved in the process of melting is called enthalpy of fusion (ΔfusH).

ΔfusS = ΔfusH/T

Similarly for vaporization at the boiling point,

ΔvapS = ΔvapH/T