Phase changes

Abstract

Each equilibrium state of a closed hydrostatic system is characterised by a set of values of pressure p volume V and temperature T. When the system consists of a single chemical species (a one-component system) for some ranges of temperature and pressure only a single phase [1] is present — that is, solid, liquid or gas. However, for other ranges of pressure and temperature two phases coexist in equilibrium, while along the triple line (see Section 13.1) all three phases coexist in equilibrium.