Will entropy increase or decrease in the following changes and give reasons for your answer ?
(i) Sugar dissolves in water (ii) Water freezes to form ice.

Answer

To determine whether entropy will increase or decrease in the given changes, we need to analyze the changes in randomness or disorder of the system during each process.

### Solution Steps:

1. **Understanding Entropy**:
- Entropy is a measure of the randomness or disorder of a system. Higher entropy means more disorder and lower entropy means more order.

2. **Case (i): Sugar dissolves in water**:
- When sugar dissolves in water, the solid sugar (which has a fixed structure) breaks down into individual sugar molecules that disperse throughout the water.
- **Change in Randomness**: The process of dissolving increases the randomness because the sugar molecules are now free to move around in the liquid state rather than being fixed in a solid state.
- **Conclusion**: Since the randomness increases, the entropy also increases. Therefore, for this case, the entropy change (ΔS) is positive.

3. **Case (ii): Water freezes to form ice**:
- When water freezes, it transitions from a liquid state to a solid state (ice).
- **Change in Randomness**: In the liquid state, water molecules are more mobile and can move freely. When they freeze, they become fixed in a structured arrangement (the solid state), which decreases their randomness.
- **Conclusion**: Since the randomness decreases, the entropy also decreases. Therefore, for this case, the entropy change (ΔS) is negative.

### Final Answers:
- (i) Entropy increases when sugar dissolves in water.
- (ii) Entropy decreases when water freezes to form ice.