When energy is added or removed from a substance, phase shifts, or transformations from one phase to another, occur.
A phase transition occurs when the molecules in a liquid have enough energy to escape from the surface.
Condensation, or the transition from gas to liquid, occurs when a molecule collides with the liquid surface and is confined by intermolecular forces in the liquid.
When the rates of condensation and evaporation are equal, a condition of dynamic equilibrium is established
The equilibrium vapor pressure is the vapor pressure measured when condensation and evaporation are in a dynamic equilibrium.
The molar heat of vaporization (Hvar), defined as the energy (typically in kilojoules) required to evaporate 1 mole of a liquid, is a measure of the strength of intermolecular forces in a liquid.