ABSTRACT
Zemansky and Dittman (1997) state that “heat is internal energy in transit.” We recognize that work, too, is energy in transit This terminology distinguishes work and heat from the amount of energy contained by a body or a system. It is then simply the amount of energy that has flowed into or out of a system or control volume during the course of a process. Internal, kinetic or potential energy is an amount of energy stored in a system, and it can be withdrawn or added to by means of the work or heat interaction with the environment around the system. Heat and irreversible work are equivalent and indistinguishable in effect, e.g., the irreversible work effected by the stirring a liquid will cause a rise of temperature and a change of state entirely equivalent to the addition of an equal amount of energy by means of heat conduction throught the wall bounding the system, say by means of a Bunsen burner.
