A system undergoes a 2-step process. In step 1, 15 J of work is done on the system as its internal energy increases by a total of 30 J. In step 2, at constant volume, the system decreases its internal energy by 20 J. Which statement is true about these changes?

From first law of thermodynamics, U q W In step 1, THERMODYNAMICS AND THERMOCHEMISTRY 60 1 U 30J w 15J In step 2, 1 U 20J Net change internal energy, U 30 20 10J which suggests that the system losses 10J of internal energy as a result in net heat flow in steps 1 &2. Thus, the correct option is (a)