So it appears there is no way to explain entropy to students in their first
algebra-based physics course that is both basically correct and
understandable to students at that level. Typically there are just a few
days on this topic. I'm not going to get very far talking about probability
spaces to kids who don't know anything about probability.
Disorder doesn't quite get it, because some apparently disordered systems
spontaneously order themselves (the salad dressing example) while
increasing entropy.
Energy dissipation doesn't get it, because it's possible to take energy in
macroscopic systems and "dissipate it" into a smaller volume within the
system as thermal energy.
What about invoking "irreversibility"? Is that a tool that works to
describe increasing entropy?