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

1. In regions with cold climate, the aquatic plants and animals can survive even when the atmospheric temperature goes below 0° C (See figure 5.7).
→ During winter, the temperature of the atmosphere can fall well below 0º C.   As the temperature decreases, the water at the surfaces of lakes and ponds starts contracting. Hence, its density increases and it goes down to the bottom. This process continues till the temperature of all the water in a lake falls to 4º C.   As the water at the surface starts cooling below 4ºC, due to anomalous behaviour of water, water starts expanding instead of contracting. Therefore, its density decreases and it remains at the surface of the lake. The temperature of the water at the surface of the lake continues to fall to 0ºC.   Finally, the water at the surface is converted into ice but the water below the layer of ice remains at 4ºC.   Ice is a bad conductor of heat. Thus, the layer of ice at the surface of the lake does not allow transfer of heat from water to the atmosphere. As the water below the layer of ice remains at 4ºC, fish and other aquatic animals and plants can survive in it.2 Marks
b. In cold regions in winter the pipes for water supply break and even rocks crack.
→ Sometimes, water enters into pipes or crevices of the rocks.   In cold regions, when the atmospheric temperature falls below 4º C, water starts expanding due to its anomalous behaviour. At 0º C, water is converted into ice and its volume increases. There is no room in the pipes or crevices for this expansion.   As a result, tremendous pressure is exerted on the pipes or rocks leading to their cracking and breaking up into small pieces. 2 Marks