State and explain the anomalous expansion of water.

Explanation

**Step-by-Step Solution:**

1. **Definition of Anomalous Expansion of Water**:
The anomalous expansion of water refers to the unique behavior of water when it cools down. Unlike most substances that contract and decrease in volume as they cool, water behaves differently between 0°C and 4°C.

2. **Behavior of Water at Different Temperatures**:
- When water is cooled from a higher temperature down to 4°C, it contracts and its volume decreases.
- However, when the temperature of water is lowered below 4°C (i.e., from 4°C to 0°C), water starts to expand instead of continuing to contract.
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