A system gives out 20 J of heat and also does 40 J of work. What is the internal energy change?

Explanation

To solve the problem, we will use the First Law of Thermodynamics, which states that the change in internal energy (ΔU) of a system is equal to the heat added to the system (Q) plus the work done on the system (W). The equation can be expressed as:

\[ \Delta U = Q + W \]

### Step-by-Step Solution:

1. **Identify the Given Values:**
- Heat given out by the system: \( Q = -20 \, \text{J} \) (negative because heat is leaving the system)
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