Which of the following is not a physical change?

Options

A. Boiling of water to give water vapour
B. Melting of ice to give water
C. Dissolution of salt in water
D. Combustion of Liquefied Petroleum Gas(LPG)

Explanation

To determine which of the following options is not a physical change, we need to understand the definition of a physical change and analyze each option accordingly.

### Step-by-Step Solution:

1. **Understand Physical Change**: A physical change is a change that affects one or more physical properties of a substance without altering its chemical composition. This means that no new substances are formed during a physical change.

2. **Analyze the Options**:
- **Option 1: Boiling of water to give water vapour**: This is a physical change. The water changes from liquid to gas (water vapour) but remains water. No new substance is formed.
- **Option 2: Melting of ice to give water**: This is also a physical change. Ice (solid water) melts to form liquid water. Again, no new substance is formed.
- **Option 3: Dissolution of salt in water**: This is a physical change as well. When salt dissolves in water, it does not create a new substance; it simply mixes with the water.
- **Option 4: Combustion of a substance**: This is a chemical change. During combustion, substances react with oxygen to form new products (e.g., carbon dioxide and water). This process involves breaking and forming chemical bonds, resulting in new substances.

3. **Conclusion**: Based on the analysis, the option that is not a physical change is **Option 4: Combustion of a substance**.

### Final Answer:
The correct answer is **Option 4** (Combustion of a substance) as it is not a physical change.

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