It expands. You change your constraints on your system, you heat it up some more, then you take the heat source away, and you put it back in contact with the atmosphere. And you cool it a little bit, change the constraints, cool it a little bit more, and heat, and you've got a closed cycle engine.

让它与大气接触冷却,改变约束，使它继续冷却，然后又再次加热,这就是循环热机，我们以前也研究过，更复杂的机器。

麻省理工公开课 - 热力学与动力学课程节选

Or I could have a non-adiabatic, I could take the same temperature change, by taking a flame, or a heat source and heating up my substance. So, clearly q is going to depend on the path.

也能改变温度，绝热指的是没有热传递，在非绝热条件下，也同样可以升温,比如用火或者热源加热，这样，q也应当与路径有关。

麻省理工公开课 - 热力学与动力学课程节选