1. The problem statement, all variables and given/known data Hi! Greetings! This is not really a problem set; I just made the question up to better understand PV diagrams of Carnot cycle. Suppose you have a gas in a container with a movable piston, but is thermally insulated. If the volume of the gas increases, is heat absorbed by the system (the gas particles) or released by the system into the environment? 2. Relevant equations [itex]dQ = dU + dW[/itex] [itex]dQ = dU + PdV[/itex] 3. The attempt at a solution Hmm.. What I am thinking is that if the volume expands, the gas particles are less compressed and have more place to move around, so I guess the system should give off heat to the surroundings?