The volume of 1 kg of helium in a piston–cylinder device is initially 5 m3 . Now helium is compressed to 2 m3 while its pressure is maintained constant at 130 kPa. Determine the initial and final temperatures of helium as well as the work required to compress it, in kJ.

Water enclosed in a rigid tank is heated from 120°C to 250°C. The pressure is high enough that the water remains subcooled (compressed) liquid during the process. Determine the thermal energy needed for the process (in kJ) if the mass of water is 8 kg. You can use water property tables or the incompressible substance assumption.

Heat transfer takes place with the surroundings such that the temperature in the tank remains constant at 300°F at all times.