Vapour–Liquid Equilibrium
The equilibrium between a liquid and its vapour in a closed container at a given temperature.
Formula / equation
p = p_saturated
Unit
Pa
In depth
At equilibrium the rates of evaporation and condensation are equal and the vapour exerts its saturated vapour pressure, which depends only on temperature. For mixtures, the composition of the vapour differs from that of the liquid, which is exactly what makes distillation possible.
Examples in the real world
A sealed bottle of water at 25 °C holding water vapour at 3.17 kPa above the liquid.