Condensation occurs when one of the three states of matter in which a gaseous (vapor) substance transforms into a liquid. It is the reverse of vaporization. As a vapor cools, it gives off energy in the form of latent heat. The release of heat causes each vapor molecule to shrink and move more slowly. Strong intermolecular forces (kinetic-molecular theory of gases) push the smaller gas molecules together; the bonding initiates the transformation into a denser, liquid form called condensate.

Condensation can occur from cooling processes such as distillation and steam engine production, or by exerting pressure in a manner that reduces the volume of the gas. Evidence of condensate is often found on a bathroom mirror after a hot shower, or on the outside of a "sweating" soda can as it warms to room temperature. Meteorological phenomena such as clouds, fog, and dew are also a result of condensation. Clouds form when rising hot air collides with air in cooler elevations.

In chemistry, condensation is defined as a reaction involving the joining of atoms in the same or different molecules. Chemists often use the process of condensation to eliminate simple molecules, such as water or alcohol, to form a heavier, more complex compound.

See Also

Evaporation; Hydrologic Cycle