Definition of enthalpy in US English:



  • 1A 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.

    • ‘We have modeled the closing kinetics and in so doing have obtained stacking enthalpies and entropies for single-stranded nucleic acids.’
    • ‘Unlike enthalpies, component entropies are nonadditive.’
    • ‘Thermogram transition temperatures, enthalpies, and widths at half-height were determined using the software provided with the calorimeter.’
    • ‘The internal energy of a system, like the enthalpy, is a state property, so it is fixed when the state of the system is specified.’
    • ‘Scanning calorimetry is used as a direct method to reveal the thermodynamic properties of phase transition like transition temperatures and enthalpies.’
    1. 1.1 The change in enthalpy associated with a particular chemical process.
      • ‘So, we can get useful work out of a system by reducing enthalpy or by increasing entropy (increasing the amount of disorder).’
      • ‘The enthalpy, entropy, and free energy changes in the opening reaction of each basepair are determined from the temperature dependence of the exchange rates.’
      • ‘The positive correlations lend support to the claim that a coupling free energy may reflect a state in which enthalpy and entropy components compensate for each other.’
      • ‘First, the volume change and the enthalpy change of the protein can be determined in time domain without temperature variation or solvent variation method.’
      • ‘In addition, melting requires significant amounts of extra heat, (in thermodynamic terms, the enthalpy of fusion), to break molecular bonds and cause a phase transition from solid to liquid.’


1920s: from Greek enthalpein ‘warm in’, from en- ‘within’ + thalpein ‘to heat’.