\b[The total <internal energy> and particle number are conserved.] The outer container is rigid and isolated, so there is no external work or heat transfer. Its total volume stays $V_0$, while the volume accessible to the gas increases from $V_0/3$ to $V_0$. Neither the gas <temperature> nor its <entropy> is generally conserved: this is an irreversible <free expansion>, with increasing <entropy>.

Solution

Past exam of the physics course of the year 4 of the natural sciences course of the University of Cambridge / 2016 / Paper 1 / Section B / B2 / b / Solution

 Solution (source code)