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Bound energy

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Bound energy


The bound energy change in a closed system is that part of the total energy change that is always bound to an exchange of heat,

dB = dU - dA [Eq. 1]
B = ∆H - ∆G [Eq. 2]

The free energy change (Helmoltz or Gibbs; dA or dG) is the total energy change (total inner energy or enthalpy, dU or dH) of a system minus the bound energy change.

Therefore, if a process occurs at equilibrium, when dG = 0 (at constant gas pressure), then dH = dB, and at deW = 0 (dH = deQ + deW; see energy) we obtain the definition of the bound energy as the heat change taking place in an equilibrium process (eq),

dB = T∙dS = deQeq [Eq. 3]

Abbreviation: B [J]


  • From Kubo 1976 North-Holland: "Free energy" is due to H. van Helmholtz (1882), and means that part of the internal energy that can be converted into work, as seen in the equation dF = dA for an isothermal quasi-static process. It was customary to call the remaining part, TdS, of the internal energy, dU = dF+TdS, the gebundene Energie (bound energy), but this is not so common now.
  • The term bound energy helps to resolve one of the historic battles in thermodynamics [2].


  1. Kubo R (1976) Thermodynamics. An advanced course with problems and solutions. North-Holland Amsterdam, New York. -
  2. Gnaiger E (1994) Negative entropy for living systems: controversy between Nobel Laureates Schrödinger, Pauling and Perutz. In: What is Controlling Life? (Gnaiger E, Gellerich FN, Wyss M, eds) Modern Trends in BioThermoKinetics 3. Innsbruck Univ Press: 62-70. - »Bioblast link«

MitoPedia concepts: Ergodynamics