There are two identical chambers,completely thermally insulated from surroundings. Both chambers have a partition wall dividing the chambers into 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 into the vacuum.
Statement $-1$: No change in the temperature of the gas takes place when an ideal gas expands in a vacuum. However,the temperature of a real gas goes down (cooling) when it expands in a vacuum.
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.

• A
  Statement $-1$ is false and Statement $-2$ is true.
• B
  Statement $-1$ and Statement $-2$ both are true. Statement $-2$ is the correct explanation of Statement $-1$.
• C
  Statement $-1$ is true and Statement $-2$ is false.
• D
  Statement $-1$ and Statement $-2$ both are true. Statement $-2$ is not the correct explanation of Statement $-1$.