- I am trying to understand the trends in the Temperature vs specific volume plot for water at constant and different pressures
I set up an experiment where I put a fixed quantity of water in a cylinder fitted with a movable piston. I slowly add heat to the system, as expected both the temperature and the volume will increase but the volume will not increase significantly (steep line), until some point where some gas bubbles begin to form, Volume increases most shallow (Temperature=constant) if I plot a graph of Temperature vs Volume. Heating beyond the point(last drop of liquid)results in a less steep curve in comparison to heating liquid water at the point where the first bubble vapor forms I add equal amounts of heat to a vapor and a liquid of the same pure substance keeping the pressure=constant the change in the gaseous state will be higher, vapor molecules have more kinetic energy thus expand at a higher rate. But repeating the same experiment at different pressures at the same initial temperature as the one conducted previously. In one case the pressure above the piston is higher than atmospheric pressure then the volume at the initial state is slightly lower. Qualitatively the same thing will happen but does vaporization occcur at a higher temperature and higher specific volume because the pressure the vapor molecules push against is higher so they must have enough K.E to do and once these molecules acquire such K.E they must have a higher velocity than at the saturation temperature for the experiment conducted previously? If I do a force balance on the piston how is the pressure =constant although more vapor molecules are produced and thus pressure must increase?