Question

The …………………….of water enables aquatic plants to survive in a reservoir where the surface layer of water has frozen.

Answer 1

Hint : We know that aquatic plants can survive in fresh water for many days but when the water becomes dirty or has been frozen, it becomes difficult for the aquatic plants to survive for a long period of time. So we should not contaminate our fresh water resources and when the water has frozen then what to do with it we will explain it in the below section.

Complete Step By Step Answer:
The anomalous expansion of water enables aquatic plants to survive in a reservoir where the surface layer of water has frozen. It is not harmful for the aquatic plants as it helps them to remain intact during very cold weather. During the very cold weather the top layer of the ponds contracts, and thus becomes denser and sinks to the bottom. Now until the entire water in the pond reaches its maximum density at ${4^0}C$ till that we set up the circulation. Now if the temperature increases, the top layer expands and remains at the top till it freezes.

Note :
We all know that when water is heated or cooled between ${0^0}C$ and ${4^0}C$ , it starts showing anomalous behavior. Water is an exception here as when we cool any substance it gets contracted but water gets expanded. Water contracts when it cooled up to just ${4^0}C$ like other liquids do but when we cool it further, it begins to expand and this expansion occurs at ${0^0}C$ and at this temperature water has maximum volume and therefore minimum density.