1. A thermodynamic quantity equal to the sum of a system's internal energy and the product of its pressure and volume; a measure of the total heat content of a substance.
Usage: technical; chemistry and physics; symbol: H

Examples

• The enthalpy change during a chemical reaction tells us how much heat is absorbed or released.
• In thermodynamics, enthalpy is used to calculate the energy requirements of industrial processes.
• The enthalpy of combustion measures the heat released when a fuel burns completely.
• Students learn to calculate enthalpy changes using Hess's law in chemistry class.
• The enthalpy of vaporization indicates how much energy is needed to convert a liquid to a gas.