Definition

1. Noun:
   • A thermodynamic property: Enthalpy is a measure of the total energy of a thermodynamic system. It includes the system's internal energy plus the product of its volume and pressure.
   • A state function in thermodynamics: It is a useful quantity for describing heat flow in processes occurring at constant pressure.

Usage Examples

• Noun:
  • The change in enthalpy of the reaction was measured in the laboratory.
  • Engineers calculate the enthalpy of steam to design efficient turbines.
  • A negative enthalpy change indicates an exothermic process.

Advanced Usage

• "Standard enthalpy of formation": The enthalpy change when one mole of a compound is formed from its elements in their standard states.
  • The standard enthalpy of formation for water is a well-known value.
• "Enthalpy of vaporization": The amount of energy required to transform a given quantity of a substance from a liquid into a gas.
  • The high enthalpy of vaporization of water helps moderate Earth's climate.

Variants and Related Words

• Enthalpic (adj): Pertaining to or involving enthalpy.
  • The enthalpic contribution to the free energy was significant.
• Enthalpically (adv): In a manner relating to enthalpy.
  • The reaction proceeds enthalpically downhill.

Synonyms

• Heat content: A common, less technical synonym for enthalpy, especially in the context of constant-pressure processes.
• Total heat: An older term sometimes used interchangeably with enthalpy.

Related Phrases and Concepts

• Enthalpy change (ΔH): The difference in enthalpy between products and reactants in a chemical or physical process.
  • The enthalpy change for combustion is typically large and negative.
• Enthalpy-entropy compensation: A phenomenon observed in some processes where a change in enthalpy is offset by a corresponding change in entropy.
• Bond enthalpy: The average energy required to break a specific type of chemical bond.

Noun

1. (thermodynamics) a thermodynamic quantity equal to the internal energy of a system plus the product of its volume and pressure
   • enthalpy is the amount of energy in a system capable of doing mechanical work