heat (het)

1. A high temperature; the sensation produced by proximity to fire or an incandescent object, as opposed to cold. The basis of h. is the kinetic energy of atoms and molecules, which becomes zero at absolute zero. 2. estrus 3. enthalpy [A.S. haete]
atomic h. the amount of h. required to raise an atom from 0° to 1°C; approximately the same for all elements (about 6 Cal/gram-atom).
h. of combustion the quantity of h. liberated per gram-molecular weight when a substance undergoes complete oxidation.
h. of compression h. produced when a gas is compressed.
conductive h. h. transmitted by direct contact, as by an electric pad or hot water bottle.
convective h. h. conveyed by a warm medium, such as air or water, in motion from its source.
conversive h. h. produced in a body by the absorption of waves that are not in themselves hot, such as the sun's rays or infrared radiation.
h. of crystallization the quantity of h. liberated or absorbed per mol when a substance passes into the crystalline state.
h. of dissociation the h. (expressed in calories or joules) expended in the dissociation of 1 mol of a substance into specified products.
h. of evaporation the h. absorbed in the evaporation of water, sweat or other liquid; for water it amounts to 540 cal/g at 100°C.h. of vaporization;
h. of formation the h. (expressed in calories or joules) absorbed or liberated during the (hypothetical) reaction in which a mole of a compound is formed from the necessary elements, in elemental form.
initial h. the first burst of h. produced after the beginning of a muscle twitch, described by A. V. Hill.
innate h. in ancient Greek medicine, the h. of the heart sustained by the pneuma and distributed by the arteries throughout the body.
latent h. the amount of h. that a substance may absorb without an increase in temperature, as in conversion from solid to liquid state (ice to water at 0°C), or from liquid to gaseous state (water to steam at 100°C). Cf. sensible h.
molecular h. the product of the specific h. of a body multiplied by its molecular weight.
prickly h. miliaria rubra
radiant h. h. given off from any body in the form of waves, similar to light waves but of greater wavelength.
sensible h. the amount of h. that, when absorbed by a substance, causes a rise in temperature. Cf. latent h.
h. of solution the quantity of h. absorbed or evolved when a solid is dissolved in a liquid.
specific h. the amount of h. required to raise any substance through 1°C of temperature, compared with that raising the same volume of water 1°C.
h. of vaporization h. of evaporation


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