Last modified on June 24, 2016, at 03:27


Evaporation is part of the hydrological cycle and consists of molecules shifting from a liquid to a gaseous form. This occurs both when liquids are cold as well as when they are warm. It occurs more often, however, with warmer liquids. Evaporation is all about the energy in individual molecules, not about the average energy of a system. The average energy can be low and the evaporation still continues. All liquids can evaporate at room temperature and normal air pressure. Evaporation happens when atoms or molecules escape from the liquid and turn into a vapor. Not all of the molecules in a liquid actually have the same energy. The energy you can measure with a thermometer is really an average of all the molecules in the system. There are always a few molecules with a lot of energy and some with barely any energy at all. The molecules with a lot of energy are able to build up enough power to become a gas. Once they reach that energy level, they can leave the liquid. When the molecule leaves, it has evaporated.

Evaporation Rates

The rate of evaporation increases with a decrease in the gas pressure around a liquid. Molecules move from areas of higher pressure to lower pressure. The molecules are sucked into the surrounding area, evening out the pressure. If the vapor pressure of the area increases to a specific level, the rate of evaporation will slow down.

See also