The first law of thermodynamics is concerned with the conservation of

Options

A. Total energy of a system
B. Energy changes in a system
C. Rate of a chemical change
D. Mass changes in nuclear reactions

Answer

To solve the question regarding the first law of thermodynamics and its concern with conservation, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the First Law of Thermodynamics**:
- The first law of thermodynamics states that energy cannot be created or destroyed; it can only be transformed from one form to another. This principle is known as the conservation of energy.

2. **Mathematical Representation**:
- The first law can be mathematically expressed as:
\[ \Delta U = Q - W \]
- Where:
- \(\Delta U\) = Change in internal energy of the system
- \(Q\) = Heat added to the system
- \(W\) = Work done by the system

3. **Identifying the Key Concept**:
- From the equation, we can see that the change in internal energy (\(\Delta U\)) is related to the heat added and the work done. This reinforces the idea that energy is conserved in a closed system.

4. **Choosing the Correct Option**:
- Given the options in the question, we need to identify which one reflects the conservation of energy. The correct option is the one that states the first law of thermodynamics is concerned with the conservation of energy.

5. **Conclusion**:
- Therefore, the answer to the question is that the first law of thermodynamics is concerned with the conservation of **energy**.

### Final Answer:
- The first law of thermodynamics is concerned with the conservation of **energy**.