Question

Consider a liquid in a piston apparatus that is at equilibrium with the vapor phase. in which direction should the piston be moved to decrease the number of molecules in the liquid phase?

Answer 1

the piston should be in the upmost position to allow room for material to expand, thus be in vapor state, when a gas is compressed, it liquefies, and when dealing with a piston, much like in an auto combustion engine, the piston moves up and allows oxygen to mix with vapor and explode, thus powering further movement of pistons.