Difference between revisions of "Evaporation"
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Evaporation
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The physical process by which a liquid or solid is transformed to the
gaseous state; the opposite of condensation. Also called vaporization.
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In meteorology, evaporation usually is restricted in use to the
change of water from liquid to gas, while sublimation is used for the
change from solid to gas as well as from gas to solid.
According to the kinetic
theory of gases, evaporation occurs when liquid molecules escape into the
vapor phase as a result of the chance acquisition of above average,
outward-directed, translational velocities at a time when they happen to lie
within about one mean free path below the effective liquid surface. It is
conventionally stated that evaporation into a gas ceases when the gas reaches
saturation. In reality, net evaporation does cease, but only because the
numbers of molecules escaping from and returning to the liquid are equal, that
is, evaporation is counteracted by condensation.
Energy is lost by an
evaporating liquid; and, when no heat is added externally, the liquid always
cools. The heat thus removed is termed the latent heat of vaporization.
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References
This article is based on NASA's Dictionary of Technical Terms for Aerospace Use
