Ahot sun warms the surface of a lake on a calm day. what will happen to the cold water at the bottom of the lake?

a. the cold water at the bottom will rise up and mix with the warm water at the top

b. the warm water at the top will sink down and mix with the cold water at the bottom

c. the cold water will remain at the bottom and won’t mix very much with the warm water at the top

d. both a and b are true

Answer:

c. The cold water will remain at the bottom and won’t mix very much with the warm water at the top.

Explanation:

During summer months the water at the surface of a lake gets heated up more than the water at the depths. Increase in temperature decreases the density of water.

Less dense fluids remain above denser fluids and thus the hot water remains at the top itself and doesn’t mix with the cold water at the bottom.  The situation is different in the months of winter when the surface water temperature is less than the water temperature at the bottom.

In such a situation the water at the surface moves to the bottom of the lake and water at the bottom rises to the surface. This causes the mixing of water in the lake.

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