Entropy of vaporization

The entropy of vaporization is the increase in entropy when vaporizing a substance. This is always positive since the degree of disorder increases in the transition from an organized crystalline solid or a slightly less organized liquid to the extremely disorganized structure of a gas. It is denoted as ΔS^o_vap and normally expressed in J/mol·K. Entropy of vaporisation is denoted by Sfg. In a phase change, both phases coexist in a equilibrium, so the Gibbs free energy is equal to zero. It follows that the entropy of vaporization is related to the boiling point and the enthalpy of vaporization:

$\Delta H_{vap} = T_{vap} \times \Delta S_{vap}$

See also

• Entropy of fusion
• Trouton's rule