D V fus . In integrating this expression, we have to take into account that D V vap is temperature dependent. The only difference is that the D H is the D H sub . This might be a piston which is permeable to the gas but not the liquid, or an inert gas which doesn t dissolve in the liquid. To remain in equilibrium, the chemical potential of the vapor must also increase by the same amount.
V m is the molar volume of the liquid.
The types of phase transitions we ve been discussing are only a small fraction of those possible. These transitions fall into various categories. In a first order transition there is a discontinuous change in volume, enthalpy, and entropy. In a second order transition the chemical potential is continuous, and the volume, enthalpy, and entropy are discontinuous in the first derivative. The heat capacity is discontinuous, but not infinite at the transition temperature.