Question

Explain the following:

What is the role of the anomalous behaviour of water in preserving aquatic life in regions of cold climate?

Answer 1

The anomalous behaviour of water is that from 0°C to 4°C it contracts and beyond 4°C it expands. So, the density of water is at a peak at 4°C. However, when the surrounding temperature goes down, the water in the oceans and rivers also cools down and the temperature of the whole water reaches 4°C. The water, therefore, reaches its maximum density at this temperature. Below this temperature (4°C), the water layer on the surface expands caused by anomalous behaviour of the water because of its decrease in density. Hence, this colder layer remains on top and converts into ice. This ice acts as an insulator and does not allow the temperature of the water layer below it to fall below 4°C. This ensures that a liveable temperature is maintained for aquatic life under the oceans and rivers.

Answer 2

1. In cold climate, temperature of water in ponds and lakes starts falling.
2. On getting colder, water contracts. As a result, density of water increases and it goes down. To replace it, warmer water from below rises up. This process continues till temperature of water at the bottom of pond becomes 4 C.
3. Water, due to its anomalous behaviour possesses maximum density at 4 C.
4. If the temperature lowers further, ice is formed at the surface of pond with water below it.
5. Ice being poor conductor of heat blocks the further heat exchange between atmosphere and water in the pond.
6. This prevents freezing of water below surface of ponds or lakes enabling survival of aquatic life.