I learnt that Gibbs free energy is the maximum amount of non-expansion work. But the phrase non expansion work confuses me. Work is defined as pressure times change in volume. If there is no expansion, how can work be done?

  • $\begingroup$ It's when I stair-climb the Willis Tower in Chicago each November for the Shirley Ryan AbilityLab. I certainly don't expand during the climb, but I do work against Earth's gravity. $\endgroup$ Dec 19, 2022 at 13:13
  • $\begingroup$ You do have to push aside the air you encounter as you rise that takes extra energy. Try climbing up in a tank of water with negative buoyancy. This explanation of Gibbs free energy is very non general. $\endgroup$
    – jimchmst
    Dec 20, 2022 at 0:08

1 Answer 1


Pressure-Volume work is a type of mechanical work .
There are also non-mechanical forms of work where in pressure and volume terms are not involved .
The most famous example is electrical work . The work done to move electrical charges ( like motion of electrons in a conductor) comes under this category .

  • $\begingroup$ Another example is the stirring of a liquid in a tank $\endgroup$ Jul 25, 2015 at 1:40

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