In interpreting and teaching of the laws of thermodynamics, the system and its immediate surroundings are usually combined to constitute a composite isolated system to use the principle of entropy increase for predicting the spontaneity of a process, and even of a process in the original system, which is called total entropy criterion. This paper discusses the limitations of the “total entropy criterion” by giving real examples and theoretical derivation, and points out that it is suspected of “changing the object of study”, “giving an irrelevant answer”, and a regression from the principle of entropy increase.
- Principle of entropy increase
- Second law of thermodynamics
- Total entropy criterion