What will happen to internal energy if work is done by the system?

Explanation

To determine what happens to the internal energy of a system when work is done by the system, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the First Law of Thermodynamics**:
The first law of thermodynamics states that the change in internal energy (ΔU) of a system is equal to the heat added to the system (Q) minus the work done by the system (W). This can be expressed as:
\[
\Delta U = Q - W
...