We limit our discussion to calculation of the amout of work involved when a system expands or contracts against a constant pressure.

**Calculating the Amount of Expansion
Work at Constant Pressure Associated With a Volume Change**

- Determine V,
the change in volume in cubic meters, m
^{3}, using the equation:Note: It may be necessary to convert the volumes to cubic meters.

- Determine
- Calculate
the work involved using the equation:
Note: If the pressure has units of Pascals and the volume units of m

^{3}, the work will have units of Joules. Work done by a system (as the system expands) has a negative value. Work done on a system (as the system shrinks) has a positive value.