Latent heat

Latent heat describes the amount of energy in the form of heat that is required for a material to undergo a change of phase. Two latent heats are typically described. One is the latent heat of fusion (melting), and the other is the latent heat of vaporization (evaporation).

Related Topics:
Energy - Heat - Phase - Heat of fusion - Melting - Heat of vaporization - Evaporation

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They are so named as to describe the direction of heat flow from one phase to the next:

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:solid → liquid → gas.

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The energy change is endothermic when going from solid to liquid to gas, but exothermic when going in the opposite direction.

Related Topics:
Endothermic - Exothermic

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For example, in the atmosphere when a molecule of water evaporates off the surface of any body of water, heat is transported by the water molecule into a lower temperature air parcel that contains more water vapor than its surroundings. Because energy is needed to turn water into water vapor, water vapor is a way for a body to release energy. If the water vapor is returned to a liquid or solid phase (by condensation or sublimation), the stored energy is released as sensible heat onto the surface where condensation (or sublimation) has occurred.

Related Topics:
Atmosphere - Air parcel - Water vapor - Energy - Water - Phase - Condensation - Sublimation - Sensible heat

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