Pressure-volume Work
Pressure-volume work, (or PV work) occurs when the volume, V of a system changes. PV work is often measured in units of litre-atmospheres, where 1L·atm = 101.325J. However the litre-atmosphere is not a recognised unit in the SI system of units, which measures P in Pascal (Pa), V in m3 and PV in Joule (J), where 1 J = 1 Pa-m3. PV work is an important topic in chemical thermodynamics.
For a reversible process in a closed system, PV work is represented by the following differential equation:
where
denotes an infinitesimal increment of work done by the system;
denotes the pressure inside the system and outside the system, against which the system expands; the two pressures are practically equal for a reversible process;
denotes the infinitesimal increment of the volume of the system.
Moreover,
where
denotes the work done by the system during the whole of the reversible process.
The first law of thermodynamics can then be expressed as
(In the alternate sign convention where W = work done on the system, but is unchanged.)
Read more about this topic: Work (thermodynamics)
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