We are given that the system “releases” heat of 2,500 J,
and that it “does work on the surroundings” by 7,655 J.
The highlighted words releases and does work on the surroundings
all refers to that it is the system itself which expends energy to do those
things. Therefore the action of releasing heat and doing work has both magnitudes
of negative value. Therefore:
heat released = - 2, 500 J
work done = - 7, 655 J
Which means that the total internal energy change of the
system is:
change in internal energy = heat released + work
<span>change in internal energy = - 2, 500 J + - 7, 655 J</span>
<span>change in internal energy = -10,155 J</span>
