The anomalous expansion of water refers to the unusual behavior of water where it expands upon cooling below 4°C (39.2°F) instead of continuing to contract like most other substances.

How it works:

• Normal behavior: Most liquids contract (become denser) as they cool.
• Water’s anomaly: Water reaches its maximum density at around 4°C. Below this temperature, as it cools further toward 0°C (freezing point), it expands instead of contracting.
• This means ice is less dense than liquid water, which is why ice floats on water.

Why is it important?

• It has crucial environmental and biological consequences. For example:
  • Ice forms on the surface of lakes and rivers, insulating the water below and allowing aquatic life to survive through winter.
  • This property helps regulate Earth’s climate and ecosystems.