## Essential University Physics: Volume 1 (3rd Edition)

a) We must first figure out how much energy is gained by the water: $W = mc \Delta t \\ W = (.5kg)*(4.18)(3) = 6.3 kJ$ Because the system gains 6.3 kJ, but 9kJ of work is done, it follows that the surroundings must have gained $9 - 6.3 = 2.7$ kJ of energy. b) If no energy had been lost, only the energy to increase the temperature would have been needed. This value is: $6.3$ kJ.