Reversible/Irreversible processes In the book

[Audrey Magsig 1E]

In the textbook, the irreversible process given as an example is a piston where external pressure increases but results in no movement in the piston. How does that work and how exactly is that an irreversible process?

Thanks!

[William Shu 1G]

Not 100% sure, but I think it has to do with the fact that an irreversible process is one that takes the system away from equilibrium. A reversible process would imply that infinitely small changes are occurring while the external pressure is slowly increasing, and therefore the piston would be moving to maintain equilibrium between the system and the surroundings. If the piston does not move, the system is no longer at a constant state of equilibrium, and therefore it is an irreversible process. I hope this helps!