Question

Explain the following:
a. What is the role of anomalous behaviour of water in preserving aquatic life in regions of cold climate?
b. How can you relate the formation of water droplets on the outer surface of a bottle taken out of refrigerator with formation of dew?
c. In cold regions in winter, the rocks crack due to anomolous expansion of water.

Answer 1

a. The anomalous behaviour of water is that it contracts from 0^oC to 4^oC and beyond 4^oC it expands. Thus, the density of water is maximum at 4^oC.
When the surrounding temperature falls, the water in oceans and rivers cools down and say the temperature of whole water reaches 4^oC. Thus, the water reaches its maximum density at this temperature. Below this temperature (4^oC), the water layer on the surface expands due to anomalous behaviour of water because of which it's density decreases. Thus, this colder layer remains on top and converts into ice which acts as an insulator and does not allow the temperature of water layer below it to fall below 4^oC. In this way, a liveable temperature is maintained for the aquatic life under the oceans and rivers due to the anomalous behaviour of water.

b. In both the given processes, the temperature of the air near the surface of bottle or the leaves (in case of dew formation) decreases to dew point. Thus, the air becomes saturated with water vapour. As a result, water vapour converts or condenses into tiny water droplets which appears on the surface of bottle or leaves.

c. Water has the property of expanding below 4^oC. Thus, in cold regions when the temperature falls below 4^oC, the water content present in rocks expands. Due to this expansion of water or increase in volume of water, the rocks cracks.