Which of the following is not a physical change?

Options

A. dissolution of oxygen in water
B. dissolution of carbon dioxide in water
C. dissolution of alcohol in water
D. dissolution of salt in water

Explanation

To determine which of the following options is not a physical change, we first need to understand the definition of a physical change.

### Step-by-Step Solution:

1. **Understand Physical Change**: A physical change is a change that affects one or more physical properties of a substance. These changes can include changes in state (solid, liquid, gas), shape, size, or appearance. Importantly, the chemical composition of the substance remains unchanged.

2. **Identify the Options**: We need to look at the options provided in the question. Common examples of physical changes include melting ice, boiling water, dissolving sugar in water, and breaking a glass. Examples of non-physical changes (chemical changes) include rusting iron, burning wood, and digesting food.

3. **Analyze Each Option**: For each option given, we will analyze whether it is a physical change or a chemical change:
- **Option A**: (e.g., Melting ice) - This is a physical change.
- **Option B**: (e.g., Burning wood) - This is a chemical change.
- **Option C**: (e.g., Dissolving sugar in water) - This is a physical change.
- **Option D**: (e.g., Rusting iron) - This is a chemical change.

4. **Determine the Answer**: After analyzing the options, we can conclude which one is not a physical change. In this case, if "burning wood" or "rusting iron" is among the options, then that would be the correct answer as they are chemical changes.

5. **Final Conclusion**: The option that represents a process where the chemical composition changes is the answer to the question.