vapor pressure Over any liquid or solid surface there is a certain pressure of its vapor. The magnitude of this pressure depends upon the temperature. If a liquid or solid is sealed up in an evacuated chamber, there will be dynamic equilibrium between the liquid (or solid) and its vapor, and the mass of the liquid will become constant. The vapor pressure under this condition of equilibrium is maximum and is called the saturation vapor pressure (SVP). It depends on the temperature but independent of the volume of the enclosure.