Calculate the change in internal energy of the system in kJ.

Question

If a system absorbs 40 kJ of energy and does 11 kJ of work on the surroundings, calculate the change in internal energy of the system in kJ. For your answer, only type in the numerical value with two significant figures. Do NOT include the unit (kJ).

Answer 1

∆E = q + w

q = +40 kJ (+ because heat is absorbed)

w = -11 kJ (- because the system is doing work on the surroundings)

∆E = +40 kJ + (-11 kJ) = +29 kJ (you can omit the kJ in your answer)

Answer 2

ΔE_internal = Q_in - W_out = 40kJ - 11kJ = 29 kJ