On a quiz, I was asked for the difference between reversible and irreversible processes.
For a reversible process, you can change direction at any time without disturbing equilibrium.
For an irreversible process, the macroscopic variables may not always be defined.
I was given 1/4 point for this answer. I asked the professor what the issue is with the answer, and she could not articulate a clear reason, and eventually said she'll re-think it.
Do you see a problem with my answer? If so, please explain.