International Encyclopedia of Systems and Cybernetics

As noted by J.de ROSNAY, at first sight, "there seems to exist a contradiction between the 1st. and the 2nd. Principle (of thermodynamics): the first one says that heat and energy are two magnitudes of the same kind; the other that they are not, since energy downgrades irreversibly into an "inferior", less "noble ", or of "lesser quality" energy: heat. The riddle is solved by the statistical theory. Heat is really energy. More precisely, it is a kinetic energy, resulting from the individual velocities of the molecules of a gas or from atomic vibration in solids. but, under its "heat" form, this energy is reduced to a maximally disordered state in which each individual movement becomes soon or later neutralized by the law of great numbers.

"Thus potential energy is ordered energy and heat is disordered energy"…

"In the first case the global movement of the molecules (in a gas for example) is apt to produce some work (move a piston). In the other case, there is an inefficient agitation "on the spot" and in every direction at the same time: the energy is there, but cannot be used" (1975, p.137).

In this last form it is sometimes called "anergy".

Heat is thus dispersed energy, reduced to molecular agitation. Everyday experience proves that any use of energy finally produces heat, without exception. Entropy is a measure of this downgrading.