Avertical piston-cylinder device contains water and is being heated on top of a range. during the process, 63 btu of heat is transferred to the water, and heat losses from the side walls amount to 8 btu. the piston rises as a result of evaporation, and 5 btu of work is done by the vapor. determine the change in the energy of the water for this process

The water would have a change in the energy of 50 BTU

Explanation:

Under the assumption that the piston-cylinder system is a closed system, then the conservation law of the system would be: , where is all the energy that goes into the system, is all the energy that leaves the system and, is the change of the energy of the system.For this case the energy that is feeded to the system is heat: 63 BTU.There is two ways that energy is leaving this system: 8 BTU of heat as losses through the side walls and, 5 BTU of work done by the vapor on the piston.Then the change of energy of the system is: .