The first law of thermodynamics is expressed as :

Options

A. `q + W = Delta E`
B. `Delta E = W - q`
C. `Q = Delta E - W`
D. `Q = q + Delta E`

Explanation

**Step-by-Step Text Solution:**

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

2. **Mathematical Expression**: The first law can be mathematically expressed as:
\[ \Delta U = Q - W \]
where:
- \(\Delta U\) is the change in internal energy of the system,
- \(Q\) is the heat exchanged between the system and its surroundings,
- \(W\) is the work done by or on the system.

3. **Internal Energy**: The internal energy (\(U\)) of a system is the total energy contained within it, which includes both kinetic and potential energy of all the particles in the system.

4. **Heat and Work**: In this context:
- \(Q\) represents the heat absorbed by the system from the surroundings (positive) or the heat released by the system to the surroundings (negative).
- \(W\) represents the work done on the system (positive) or the work done by the system (negative).

5. **Example of the First Law**: A practical example of the first law of thermodynamics is photosynthesis in plants. During this process, plants absorb light energy, which is then converted into chemical energy through chlorophyll. This transformation illustrates the conversion of energy from one form to another, consistent with the first law.

6. **Conclusion**: The first law of thermodynamics emphasizes the conservation of energy principle, which is crucial in understanding energy transformations in physical and chemical processes.

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