Enthalpy
A thermodynamic quantity equivalent to the total heat content of a system; it is equal to the internal energy of the system plus the product of pressure and volume.
Enthalpy (H) is particularly useful for measuring heat changes in chemical reactions or physical processes that occur at constant pressure, which is common in many real-world scenarios. It accounts for both the internal energy and the energy required to make space for the system.
Commonly confused with
- Entropy: Enthalpy measures the total heat content of a system, while entropy measures its disorder or the dispersal of energy.
- Internal Energy: Internal energy is a component of enthalpy; enthalpy also includes the pressure-volume work done by or on the system.
Word family
- enthalpic (adjective): relating to enthalpy
Collocations
- standard enthalpy
- enthalpy change
- enthalpy of reaction
- enthalpy of formation
- molar enthalpy
Example sentences
- "The negative change in enthalpy indicated that the reaction was exothermic, releasing heat into the surroundings." In a chemistry experiment.
- "Calculating the enthalpy of formation is crucial for predicting the energy balance of a new compound." Discussing thermodynamic properties.
Memory hook
ENTHALPY sounds like 'EN-HEAT-PY,' reminding you it's about the total HEAT content. Total Heat Content
When not to use
Outside of scientific or engineering contexts. It's a highly technical term with a precise definition that is not interchangeable with 'heat' or 'energy' in general conversation.
Fun facts
- Enthalpy is a state function, meaning its value depends only on the current state of the system, not on how that state was reached.
- Most chemical reactions in laboratories are performed at constant pressure, making enthalpy a very practical quantity to measure and use.
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