Question

A system absorbs 52 joules of heat and does work using 25 joules of energy. What is the change in the internal energy of the system?

Answer 1

The change in internal energy is $\Delta U=Q+W$. Where $\Delta U$ is change in internal energy. $Q$ is heat added to the system (absorbed by the system). $W$ work done on the system. $W$ is taken as positive if work is done on the system and negative if work is done by the system. Here $Q=52$ and $W=-25$, hence change in internal energy is

$\Delta U=52-25\\ \Delta U=27$

Change in internal energy of the system is 27 J. Internal energy increases.

Answer 2

B. 27 joules is correct