Heat of Vaporization

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heat of vaporization

[′hēt əv ‚vā·pə·rə′zā·shən]
The quantity of energy required to evaporate 1 mole, or a unit mass, of a liquid, at constant pressure and temperature. Also known as enthalpy of vaporization; heat of evaporation; latent heat of vaporization.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Heat of Vaporization


(or heat of evaporation, latent heat of vaporization), the amount of heat that must be supplied to a substance in an equilibrium constant-pressure and constant-temperature process to convert the substance from the liquid state to the gaseous state. The same amount of heat is liberated when the vapor condenses into a liquid.

Table 1. Heat of vaporization of several substances
Hydrogen ...............–252.61074.48 × 105
Nitrogen ...............–195.847.61.99 × 105
Ethyl alcohol ...............78.42169.05 × 105
Water ...............10053922.6 × 105
Mercury ...............35769.72.82 × 105
Lead ...............17402048.55 × 105
Copper ...............26001,15048.2 × 105
Iron32001,46061.2 × 105

The heat of vaporization is a special case of the heat of a firstorder transition. For a given substance, the heat of vaporization may be determined per unit mass or per mole. In the former case, the heat of vaporization is measured in, for example, joules per kg (J/kg) or kilocalories per kg (kcal/kg). In the latter case, the heat of vaporization may be expressed in joules per mole. The term “molar heat of vaporization” is sometimes applied to the heat of vaporization per mole. Table 1 gives the values of the heat of vaporization per kg Lv for several substances at normal external pressure (760 mm Hg, or 101,325 newtons per m2) and at the boiling point tb.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
The heat of vaporization is defined as the minimum amount of energy required to evaporate a unit of mass of water bound to the biological structure of agricultural products (Correa et al., 1998; Sousa et al., 2016).
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The calculated heat of vaporization for naphthalene was lower than the literature value.
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