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Chemistry vocabulary · Energy, Reaction Rates and Equilibrium

Enthalpy

Meaning in chemistry, with examples

/ˈenθəlpi/nounAdvanced term

In chemistry, enthalpy means: The heat content of a system at constant pressure. Chemists usually measure its change, ΔH, which shows how much heat a reaction gives out or takes in.

In Turkish: entalpi

How it is used

Used in thermochemistry and physical chemistry. You calculate the enthalpy change of a reaction, use standard enthalpies of formation or combustion, and apply Hess's law. Values are given in kJ/mol, and ΔH is read 'delta H'.

Example sentences

  1. The enthalpy change for the combustion of methane is about −890 kJ/mol.

  2. Use Hess's law to calculate the enthalpy of formation.

Common collocations

  • enthalpy change
  • standard enthalpy of formation
  • enthalpy of combustion
  • Hess's law
  • exothermicDescribes a reaction or process that releases heat to the surroundings, so the temperature rises. Its enthalpy change (ΔH) is negative.
  • endothermicDescribes a reaction or process that takes in heat from the surroundings, so the surroundings get colder. Its enthalpy change (ΔH) is positive.
  • activation energyThe minimum energy that reacting particles need to collide successfully and start a reaction. Catalysts work by lowering it.
  • chemical reactionA process in which substances change into new substances with different properties, as bonds between atoms break and new bonds form.

This word in other fields

The same English word can have a different meaning in another field:

More terms: Energy, Reaction Rates and Equilibrium

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