Liquid-vapor phase transition molar Gibbs energy

Figure 5.5 The Molar Gibbs Energy of Water as a Function of Temperature Near the Liquid-Vapor Phase Transition (Schematic).

Phase transitions are classified according to the partial derivatives of the Gibbs energy. Ordinary phase transitions such as vaporizations, freezings, and so on, are called first-order phase transitions, which means that at least one of the first derivatives dG /dT) p or (dGta/dP)T is discontinuous at the phase transition. In most first-order transitions, both of these derivatives are discontinuous. From Chapter 4 we know that (9Gm/9r)/> is equal to -5m and that (9Gm/9F)r is equal to Fm- Figure 5.7 shows schematically the molar volume as a function of pressure as it would appear for a solid-liquid or a solid-solid transition. Figure 5.8 shows schematically the molar entropy as a function of temperature as it would appear for a liquid-vapor transition. 

---