If a Gas Expands Freely into a Vacuum

Multiple Choice

If a gas expands freely into a vacuum,

A) the expansion is adiabatic, so the gas does work on its environment and its internal energy decreases.
B) the expansion is isothermal.
C) the expansion is occurs at constant pressure.
D) the expansion is adiabatic but no work is done, so the internal energy of the gas and its temperature both decrease.
E) the expansion is adiabatic but no work is done, so the internal energy of the gas and its temperature do not change.