We're learning about entropy right now in general chemistry, and I'm trying to understand something.
From the fact that entropy can be directly compared with enthalpy, free energy, electromotive force, etc., and its being measured in units of $\pu{J//mol*K}$ – including joules, the units of energy – it would seem that entropy is some form of energy. By the first law of thermodynamics, then, entropy can't be created nor destroyed, only transformed and transferred. From Gibbs' equation we see that entropy is being transformed out of the molecular potential energy, and from Clausius' equations we see that entropy can be transferred between a system and its surroundings, with $\Delta S_\mathrm{system}=-\Delta S_\mathrm{surroundings}$. Since $\Delta S_\mathrm{universe}=\Delta S_\mathrm{system}+\Delta S_\mathrm{surroundings}$, it follows that $\Delta S_\mathrm{universe}=0$ – as one would expect from the first law.
Yet the second law of thermodynamics states that $\Delta S_\mathrm{universe}>0$.
- If entropy is a form of energy, then how can universal entropy tend to increase?
- If entropy is not a form of energy, then how can it be compared with actual forms of energy and measured in energy units?