1.14.76: Work

This term ‘work’ makes it first key appearance (at least in thermodynamics) in the context of the statement that if work is done on a closed system the thermodynamic energy of the system increases given that heat q is zero. This simple statement understates the complexity of the term ‘work’ in thermodynamics.

In general terms work done on a closed thermally insulated system raises the energy of that system and is given by the product of intensive and capacity factors [1]. Three examples make the point.

The analysis is complicated by the fact that changes in a given system can take one of two limiting forms; e.g. frozen and equilibrium. In the case of surface tension, frozen ( plastic) surface tension describes the case where the intermolecular distances in the surface increase. The equilibrium case describes the case where molecules in the bulk phase and in the surface exchange to hold the change in the surface as a reversible (equilibrium) process.

Footnote

[1] E. F. Caldin, Chemical Thermodynamics, Clarendon Press, Oxford, 1958.

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