A gas is initially contained inside an insulated container A, at initial conditions P1, V1, m, and T1. These quantities represent pressure, volume, mass, and temperature, respectively. A valve is then opened which allows the gas to expand freely into an insulated container B, which is initially empty. After the gas has settled, the final conditions of the gas are P2, V2, m, and T2. In thermodynamics, a process is said to be reversible if it produces no entropy. This means that the process can happen in the reverse direction. Explain why the process described is not reversible.