The process of evaporation in a closed container will proceed until there are as many molecules returning to the liquid as there are escaping. Since the molecular kinetic energy is greater at higher temperature , more molecules can escape the surface and the saturated vapor pressure is correspondingly higher. If the liquid is open to the air, then the vapor pressure is seen as a partial pressure along with the other constituents of the air . The temperature at which the vapor pressure is equal to the atmospheric pressure is called the boiling point .
Ordinary evaporation is a surface phenomenon - some molecules have enough kinetic energy to escape.
If the container is closed, an equilibrium is reached where an equal number of molecules return to the surface. The pressure of this equilibrium is called the saturation vapor pressure . In order to evaporate, a mass of water must collect the large heat of vaporization, so evaporation is a potent cooling mechanism. Evaporation heat loss is a major climatic factor and is crucial in the cooling of the human body. Thermodynamics Go Back Evaporation vs Boiling Ordinary evaporation is a surface phenomenon - since the vapor pressure is low and since the pressure inside the liquid is equal to atmospheric pressure plus the liquid pressure , bubbles cannot form.