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.

A natural process such as a phase change will occur when the associated change in the Gibbs free energy is negative. It follows that the standard entropy change of vaporization is related to the boiling point and the standard enthalpy change of vaporization:

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

See also

• Entropy of fusion
• Trouton's rule