How Harmful Is the First Law?

Abstract: In his First Law (of thermodynamics), Clausius emphasized the equivalence of heat and work—conservation of energy was mentioned only indirectly. Today, the main emphasis is put on energy conservation, but the equivalence of heat and work has proven not only to be superfluous, but also highly destructive. Because of this emphasis, heat is no longer considered an independent entity. In the guise of the quantity Q heat acts in a strange double role—an entity equivalent to work, but also as something fundamentally different. The place formerly occupied by heat is now filled with an abstract quantity, the entropy S—a phantom without macroscopically relevant properties. By using a phenomenological approach to entropy, it can be shown that entropy S does indeed have easily comprehensible macroscopic properties. This approach can be used to simplify thermodynamic reasoning and to reduce the calculus of thermodynamics to a fraction of its usual extent.