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 (Δ_fusH).

Δ_fusS = Δ_fusH/T

Similarly for vaporization at the boiling point,

Δ_vapS = Δ_vapH/T