This is a point that is often confusing, because you can think, well maybe I could calculate what the internal pressure is even for this very rapid process.

这一点可能让你们很困惑，因为你们可以想象这个过程，我也可以计算在这快速的变化中,内部压强是多大。

麻省理工公开课 - 热力学与动力学课程节选

It's going to take place in there. It's going to be a constant pressure, it might be open to the air, or even if it isn't, there might be plenty of room, and it's a liquid anyway, so the pressure isn't going to change significantly.

也许它是液体，它在这个位置,这是恒压的，它也许是连通大气的，就算不是，它也有，足够的空间，而它是液体,压强不会显著地改变。

麻省理工公开课 - 热力学与动力学课程节选

The pressure could not be, might not even be constant throughout the system.

很可能气体各处的压强,都不相同。

麻省理工公开课 - 热力学与动力学课程节选

The atoms or molecules in the gas don't know that there are other atoms and molecules in the gas, and then you end up with this universal property. All right, so gases that have this universal property, even when the pressure is not zero, those are the ideal gases.

可以忽略,这样就得到了理想气体的性质,在有限压强下,依然能保持这些性质的气体，被称为理想气体，本课中我们把大部分气体，都作为理想气体来处理。

麻省理工公开课 - 热力学与动力学课程节选