A substance is contained within a simple piston-cylinder arrangement, perfectly insulated from the external environment, at a pressure,temperature,volume combination where it exists as a saturated liquid-vapour. If I now expand the volume using the piston, more of the liquid phase should boil and change to vapour in order to occupy the expanding volume. Is this a constant pressure, consant temperature process? , how is it effected by the rate of change of volume? Similarly, if I now recompress the volume, will the gaseous phase re-condense? , or will the gaseous phase be inclined to compress adiabatically and become a locally superheated vapour until it has time to give up heat to the liquid? I can handle basic thermodynamics but I am confused on this one as I think there are internal heat transfers required between the phases and the rate of expansion/compression must have implications on this being a constant temperature, constant pressure process. Can anyone shed light on this, or have experimental experience on what might happen?