The Second Law

The second law states that entropy is a state function and--if added up for all parts of system--never decreases. This turns out to be incredibly useful, since if we want to find the condition that a system stops changing (i.e., when it is in equilibrium) then the entropy of the entire system is as large as possible.

It is also difficult to apply because it forces us to consider everything that may be affected by a process and not the little bit of material in which we may be interested.

There are many different ways to state the second law and they all sound quite different from each other. This fact is not terribly enlightening, but showing that all the differing statements are consistent is terribly enlightening.