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Work [J] is a specific form of energy, called exergy, performed by a closed or open system on its surroundings (the environment). This is the definition of external work, which is zero in isolated systems. The term exergy includes external and internal work. Mechanical work is force [N] times path length [m]. The internal-energy change of a closed system, dU, is due to external exchange (e) of work and heat, and work is the internal-energy change minus heat,

detW = dU - deQ

Abbreviation: deW [J]

Reference: Gnaiger (1993) Pure Appl Chem

Communicated by Gnaiger E 2018-10-20; last update 2019-01-06

Pressure-volume work

Pressure-volume work, dVW, at constant pressure, is the gas pressure, p [Pa = J·m-3], times change of volume, dV [m3],
dVW = -p·dV [J]
The available work, deW, is distinguished from external total work as [1]
deW = detW - dVW
The enthalpy change, dH, at constant pressure, is defined as internal-energy change minus pressure-volume work,
dH = dU - dVW


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»Bioblast links: Energy and exergy - >>>>>>> - Click on [Expand] or [Collapse] - >>>>>>>
  • Joule [J]; 1 J = 1 N·m = 1 V·C; 1 cal = 4.184 J
Fundamental relationships
» Energy
» Exergy
» Extensive quantity
» Force
» Pressure
» Intensive quantity
Forms of energy
» Internal-energy, dU
» Enthalpy, dH
» Heat, deQ
» Bound energy, dB
Forms of exergy
» Helmholtz energy, dA
» Gibbs energy, dG
» Work, deW
» Dissipated energy, diD


  1. Gnaiger E (1993) Nonequilibrium thermodynamics of energy transformations. Pure Appl Chem 65:1983-2002. - »Bioblast link«

MitoPedia concepts: Ergodynamics