ABSTRACT
This chapter describes the surface by only two independent variables, the surface area and the temperature. For a system involving a single component, the surface tension will depend only on the temperature and will be independent of the area. The surface systems are, in fact, simpler than the PVT systems because engineers have taken the surface tension to be independent of area. The entropy and the temperature remain as important variables, and this system can also be taken through a Carnot cycle. The more general equation can be applied locally to nonspherical surfaces such as a large mercury droplet resting on a glass plane, and it also applies to nonequilibrium situations, which might be found in the fluid mechanics of systems involving curved interfaces.
