enthalpy

[en-thal-pee, en-thal-]
noun, plural enthalpies. Thermodynamics.
a quantity associated with a thermodynamic system, expressed as the internal energy of a system plus the product of the pressure and volume of the system, having the property that during an isobaric process, the change in the quantity is equal to the heat transferred during the process. Symbol: H
Also called heat content, total heat.


Origin:
1925–30; < Greek enthálp(ein) to warm in (en- en-2 + thálpein to warm) + -y3

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World English Dictionary
enthalpy (ˈɛnθəlpɪ, ɛnˈθæl-)
 
n
H, heat content, Also called: total heat a thermodynamic property of a system equal to the sum of its internal energy and the product of its pressure and volume
 
[C20: from Greek enthalpein to warm in, from en-² + thalpein to warm]

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Word Origin & History

enthalpy
1927, from Gk. enthalpein to warm, from en- in + thalpein to heat.
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Medical Dictionary

enthalpy en·thal·py (ěn'thāl'pē, ěn-thāl'-)
n.
A thermodynamic function of a system, equivalent to the sum of the internal energy of the system plus the product of its volume multiplied by the pressure exerted on it by its surroundings.

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American Heritage
Science Dictionary
enthalpy   (ěn'thāl'pē)  Pronunciation Key 
A partial measure of the internal energy of a system. Enthalpy cannot be directly measured, but changes in it can be. If an outside pressure on a system is held constant, a change in enthalpy entails a change in the system's internal energy, plus a change in the system's volume (meaning the system exchanges energy with the outside world). For example, in endothermic chemical reactions, the change in enthalpy is the amount of energy absorbed by the reaction; in exothermic reactions, it is the amount given off. See also thermodynamics.
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Example sentences
Enthalpy is a function of temperature and pressure not the state of the substance.
What is increasing is the enthalpy of the planetary surface.
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