Free expansion of an ideal gas by kinetic gas theory

Summary: In this article, the authors discuss the difficulties students face with the second law of thermodynamics based on a survey. They address these issues by clarifying the concepts of system entropy, reservoir entropy, total entropy, and entropy of the Universe. They also differentiate between internally reversible, totally reversible, and irreversible processes. By establishing the increasing entropy principle as the quantitative expression of the second law, they highlight the importance of total entropy in macroscopic thermodynamics. This analysis helps students understand the limitations imposed by the second law.