Hello, I just have a question. When a gaz expands against a piston (that is insulated), the system is doing work so W>0 and we know that the volume will increase and the pressure decrease. But what I want to know, is how about the temperature, I'd say that it will decrease since the pressure also decreases , but is there any other argument ? I know that if we want to maintain a constant temperature in such a system we have to "connect" the system to a tank , so that the heat transfer will compensate the work done by the system. Thanks !