What Is Meant by a Saturated Liquid and Vapor?

By Staff WriterLast Updated Mar 25, 2020 1:57:31 PM ET

When a vapor or liquid in a closed environment reaches an equilibrium between the amount of evaporating, condensing and returning molecules, the liquid or vapor is saturated. Saturated vapor is also known as dry vapor.


Evaporation of a liquid into a vapor occurs more rapidly at high temperatures, as molecular kinetic energy is increased if temperature rises. The increase in this energy results in the escape of more vapor molecules, which increases the saturated vapor pressure. When the temperature of a liquid is raised to a certain point and the pressure is at the correct levels, the transition of liquid to vapor is removed and turns into one fluid process of evaporation into condensation.

This process repeats itself continuously if the correct heat and pressure are maintained. When all vapor is condensed, the liquid becomes saturated. Similarly, when all liquid is evaporated, it becomes saturated vapor. The critical temperature and pressure for water are 374 degrees Celsius and 220 Atmospheres, respectively.

If heat is added to a saturated vapor, the result is called superheated vapor. If a liquid is boiled in an open environment, the vapor pressure is taken into account as partial pressure along with the properties of the surrounding air. The liquid reaches its boiling point when the vapor pressure is equal to the atmospheric pressure.