Effects of Curved Interfaces on Phase Equilibria and Nucleation

5 EFFECTS OF CURVED INTERFACES ON PHASE EQUILIBRIA AND NUCLEATION THE KELVIN EQUATION 

In addition to capillarity, another important consequence of the pressure associated with surface curvature is the effect it has on the thermodynamic activity of substances. As a consequence, phase equilibria (including dissolution of chemical species in the different phases) are affected by the presence of interfaces. In this section we consider a few such cases. 

The influence of curvature on phase equilibria is most readily understood for liquids, for which the activity is measured by the vapor pressure of the liquid. Accordingly, suppose we consider the process of transferring molecules of a liquid from a bulk phase with a vast horizontal surface to a small spherical drop of radius Rs. 

According to Equation (32), no pressure difference exists across a plane surface the pressure is simply p0, the normal vapor pressure. However, a pressure difference given by Equation (30) exists across a spherical surface. Therefore for liquid-vapor equilibrium at a 

When liquid and vapor are at equilibrium, these two values of AG are equal  

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