There are two identical chambers, completely thermally insulated from surroundings. Both chambers have a partition wall dividing the chambers in two compartments. Compartment $1$ is filled with an ideal gas and Compartment $3$ is filled with a real gas. Compartments $2$ and $4$ are vacuum. A small hole (orifice) is made in the partition walls and the gases are allowed to expand in vacuum.
$\mathrm{Statement-1:}$ No change in the temperature of the gas takes place when ideal gas expands in vacuum. However, the temperature of real gas goes down (cooling) when it expands in vacuum.
$\mathrm{Statement-2:}$ The internal energy of an ideal gas is only kinetic. The internal energy of a real gas is kinetic as well as potential.