Question

How will you explain following statement with the help of the anomalous behaviour of water?

In regions with cold climate, the aquatic plants and animals can survive even when the atmospheric temperature goes below 0°C (See the figure).

Answer 1

Water shows anomalous behaviour because it is most dense at 4°C. When the temperature falls below 4°C, water expands and becomes less dense.

• In winter, the surface water cools first.
• Water at 4°C sinks to the bottom because it is the heaviest.
• As the surface temperature falls below 4°C, this water becomes lighter and remains on the surface.
• At 0°C, the surface water freezes, forming a layer of ice.
• The ice floats because it is less dense than liquid water.
• The ice layer acts as an insulator, preventing the water below from freezing.
• Therefore, the water beneath the ice stays at about 4°C, allowing aquatic plants and animals to survive even when the atmospheric temperature is below 0°C.