Explain how it is possible to compress a sample of gas to half its original volume without changing the pressure.

Estimate the change in temperature when one cubic meter of air is compressed to half its original volume adiabatically (start at room temperature and pressure).

Is melting an ice cube an irreversible process? How about freezing one?

Estimate the total work by a system taken around the cycle shown in the figure. Does the system have to be an ideal gas?