Editing Entropy (section)

=== Phase transitions ===
Reversible [[phase transition]]s occur at constant temperature and pressure. The reversible heat is the enthalpy change for the transition, and the entropy change is the enthalpy change divided by the thermodynamic temperature.<ref>{{cite book|first=Michael E.|last=Starzak|date=2010|chapter=Phase Equilibria & Colligative Properties|chapter-url=https://books.google.com/books?id=cw0QV7l559kC&pg=PA138|title=Energy & Entropy: Equilibrium to Stationary States|pages=138–140|isbn=978-1489983671|publisher=Springer Science+Business Media|access-date=5 September 2019}}</ref> For fusion (i.e., [[melting]]) of a solid to a liquid at the melting point <math display="inline">T_\mathsf{m} </math>, the [[entropy of fusion]] is:<math display="block">\Delta S_\mathsf{fus} = \frac{\Delta H_\mathsf{fus}}{T_\mathsf{m}}.</math>Similarly, for [[vaporisation]] of a liquid to a gas at the boiling point <math>T_\mathsf{b}</math>, the [[entropy of vaporization|entropy of vaporisation]] is:<math display="block">\Delta S_\mathsf{vap} = \frac{\Delta H_\mathsf{vap}}{T_\mathsf{b}}</math>