Write a "P" if the description describes a Physical Change, and a "C" if it describes a Chemical Change.

1) Burning a piece of wood.
2) Ripping a piece of paper.
3) A nail that has rusted.
4) Water that has frozen.

Air is contained in a variable-load piston-cylinder device equipped with a paddle wheel. initially, air is at 400 kpa and 17°c. the paddle wheel is now turned by an external electric motor until 75 kj/kg of work has been transferred to air. during this process, heat is transferred to maintain a constant air temperature while allowing the gas volume to triple. calculate the required amount of heat transfer in kj/kg.