Surface Thermodynamics

Abstract

When a system exists in a two-phase state, surface tension is exhibited at interfaces. Let us consider in particular a gas-liquid system consisting of a single liquid drop in contact with a gas. Let s be the surface tension, and Σ the total interface area. It is possible to do work on such a system without changing its volume, but simply changing its interface area. For instance, the total rate of work done on the system can be expressed as

$$W_{\mathrm{t}}\;=\;pV_{\mathrm{t}}^{\cdot}+s\Sigma ^{\cdot}$$

((6.1.1))

The boundaries between phases are not surfaces in a strict mathematical sense, but are very thin regions, in which the properties change with great abruptness from the properties of the one homogeneous phase to those of the other. Ordinarily these thin transition regions between phases contain relatively so small an amount of substance that they may be entirely ignored. But when we study surface tension, adsorption, and kindred phenomena, they become of great importance.

G. N. Lewis and M. Randall