If 30 kJ of heat flows into a system and the internal energy increases by 15 kJ,then what is the work done by or on the system?
A) +85 kJ
B) +65 kJ
C) -65 kJ
D) +15 kJ
E) -15 kJ

Question

Quizplus · Accepted Answer

According to the first law of thermodynamics, the change in internal energy (ΔU) is equal to the heat added to the system (Q) minus the work done by the system (W): ΔU = Q - W. Here, ΔU = 15 kJ and Q = 30 kJ. Solving for W gives W = Q - ΔU = 30 kJ - 15 kJ = 15 kJ. Since the internal energy increased, the work done is negative, indicating work done on the system, so W = -15 kJ.

If 30 KJ of Heat Flows into a System and the Internal