In thermodynamics, a reversible process is one that happens near equilibrium and with minimal dissipation. In a reversible process, a tiny change in some variable can be put back with the same effort that made it. Phase boundaries are well-modeled as reversible processes: the amount of energy it takes to melt an amount of ice is the same amount it takes to re-freeze it. Strictly, no process is truly reversible, but a model of a reversible process gives us the most efficient version of it, and...
