enthalpy
EN-thal-pee
/ˈɛnθælpi/
A thermodynamic quantity equivalent to the total heat content of a chemical or physical system, equal to the internal energy plus the product of pressure and volume.
Enthalpy is a state function used to track heat flow in systems at constant pressure. A change in enthalpy tells scientists whether a reaction absorbed or released heat.
The story behind the word. Coined in 1909 by Dutch physicist Heike Kamerlingh Onnes, 'enthalpy' was constructed from the Greek 'enthalpein', meaning 'to warm inside'. It perfectly captures the concept of measuring the internal heat content of a system.
Word relationships
- heat content: Heat content is an informal, conceptual term, whereas enthalpy is a precise, mathematically defined thermodynamic property.
Commonly confused with
- entropy: Enthalpy is the total heat energy of a system, while entropy is a measure of how spread out or disordered that energy is.
Word family
- enthalpic (adjective): Relating to or characterized by enthalpy.
Collocations
- change in enthalpy
- specific enthalpy
- enthalpy of vaporization
- enthalpy of reaction
Example sentences
- "The change in enthalpy during a chemical reaction is equal to the heat absorbed or released at constant pressure." Chemical thermodynamics textbook
- "Calculating the enthalpy of steam is crucial for designing efficient power generation turbines." Advanced engineering research paper
Memory hook
Think of 'enthalpy' with an 'H' for 'Heat content', and 'entropy' with an 'O' for 'disOrder'. Total heat content inside.
When not to use
Do not confuse with 'entropy' (which measures disorder) or 'temperature' (which measures average kinetic energy).
Fun facts
- Heike Kamerlingh Onnes, the physicist who coined 'enthalpy', also discovered superconductivity and was the first person to liquefy helium, earning him a Nobel Prize.
Related words
Also appears in
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