The anomalous expansion of water occurs in the range

1. Analyze the question The question asks for the temperature range over which water behaves "anomalously" when heated, meaning it does something different from most liquids.

2. Explain the concept Most substances expand when heated and contract when cooled. Water does not follow this rule over one small range:

• When water is heated from 0 °C to 4 °C, it contracts instead of expanding. Its volume decreases and its density increases.
• At 4 °C, water has its minimum volume and maximum density (about 1000 kg/m³).
• Above 4 °C, water expands normally as the temperature rises.

This unusual contraction between 0 °C and 4 °C is called the anomalous expansion of water.

3. Work through the options

• A. 0 °C to 100 °C: Wrong. Above 4 °C water expands normally, so this range is too wide.
• B. 0 °C to 4 °C: Correct. This is where water contracts on heating.
• C. 4 °C to 100 °C: Wrong. This is the normal expansion range.
• D. -4 °C to 0 °C: Wrong. Below 0 °C, water has already become ice.

4. Answer The anomalous expansion of water occurs between 0 °C and 4 °C, which is option B.

5. Why it matters (and an exam tip) Because water is densest at 4 °C, the densest water sinks to the bottom of a freezing pond. Ice forms at the top, and fish survive in the water underneath at about 4 °C.

Memory trick: "Water is weird from zero to four." Remember that 4 °C means maximum density and minimum volume.