Question

A vertical piston-cylinder device contains water and is being heated on top of a range. During the process, 10 kJ of heat is transferred to the water, and heat losses from the side walls amount to 80 J. The piston rises as a result of evaporation, and 2 J of work is done by the vapor. Determine the change in the energy of the water for this process.

Answer 1

Answer: 9.9KJ

Explanation: Q = U + W + losses

Q is heat transfered to the water

U is the change in energy of the system

W is work done by the system = 2J

Losses = 80J

Heat into system is 10kJ = 10000KJ

Therefore

U = Q - W - losses

U = 10000 - 2 - 80 = 9990J

= 9.9kJ