Hello there, Sorry, if there's a thread about this already. Let's say if i have Piston which is fully insulated because as mentioned, it is an adiabatic compression. The pressure will increase as the volume of decrease. But what really happened when the system is compressed over the critical point. In pv diagram, will the pressure: a. Remain constant b. Increase exponentially c. Decrease d. drop to 0 in a straight line The temperature is assumed to be not constant. My idea would be 'c' or 'd' because of phase change from gas to liquid. However, I couldn't understand the kinetic theory behind it. Thanks for any help.