What happens to the internal energy of a system if work is done by the system?

Explanation

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

### Step 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 in the formula:
\[ \Delta U = Q - W \]

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