Entropy of fusion

The entropy of fusion is the increase in entropy when melting a substance. This is almost always positive since the degree of disorder increases in the transition from an organized crystalline solid to the disorganized structure of a liquid; the only known exception is helium. It is denoted as ${\displaystyle \Delta S_{\text{fus}}}$ and normally expressed in J mol⁻¹K⁻¹

A natural process such as a phase transition will occur when the associated change in the Gibbs free energy is negative.

Since this is a thermodynamic equation, the symbol T refers to the absolute thermodynamic temperature, measured in kelvins (K).

Equilibrium occurs when the temperature is equal to the melting point ${\displaystyle T=T_{f}}$ so that

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