I was wondering what causes the difference between adiabatic expansion and Joules expansion? Because to me both seems to same. In a sense that in case joules expansion we open the valve in order to let gas expand on its own. In this case after a while the pressure inside the chamber change, volume change but not the temperature. If I imagine the molecules seems to travel at same speed even if we let the valve open which causes the velocity of the particles to remain same. So I want to know why cant I imagine same thing in case of adiabatic expansion ? Can you please help me understand this