SUMMARY
Energy can cross the boundaries of a closed system in the form of heat or work. For control volumes, energy can also be trans- ported by mass. If the energy transfer is due to a temperature difference between a closed system and its surroundings, it is
Work is the energy transferred as a force acts on a system through a distance. The most common form of mechanical work is the boundary work, which is the work associated with the expansion and compression of substances. On a P-V diagram, the area under the process curve represents the boundary work for a quasi-equilibrium process. Various forms of work are expressed as follows:
