A system absorbs 187 kJ of heat and the surroundings do 120 kJ of work on the system. What is the change in internal energy of the system?

1 Answer

• When the system does work on its surroundings, energy is lost, and delta E is negative.

  When the surroundings do work on the system, the internal energy of the system becomes larger, so delta E is positive.

  Delta E = q + w

  System absorbs heat : q = +187

  Work done on the system, the number is positive. w = +120

  Delta E = 187 kJ + 120 kJ = 307 kJ