|(no longer in technical usage) the heat evolved or absorbed by unit mass (specific latent heat) or unit amount of substance (molar latent heat) when it changes phase without change of temperature|
|latent heat |
The quantity of heat absorbed or released by a substance undergoing a change of state, such as ice changing to liquid water or liquid water changing to ice, at constant temperature and pressure. The latent heat absorbed by air when water vapor condenses is ultimately the source of the power of thunderstorms and hurricanes. See also heat capacity.
The heat released or absorbed when matter undergoes a change of phase (see phases of matter). If the heat is given off during the change from a liquid to a solid, it is called heat of fusion. If it is given off during the change from a gas to a liquid, it is called heat of vaporization.