CHEMISTRY COMMUNITY

Can be volume change in a closed system?
I read that there can be, for example if there's a piston but I'm not sure. But if that's true then why on #2 in the midterm is U=0 in a closed system if the volume can change? Even though q=0, can't there be work?

Closed system just means that energy can be added/removed, and this can happen by heating or compression. So yes. In an open system, on the other hand, matter can be added/removed as well as energy.

So what’s an example of a closed system?

In section 8.1 of the book, it gives an example of a closed system: a cold pack. Energy can be exchanged, but not matter.