Multiple choice

The surface of a lake is frozen in severe winter, but the water at its bottom is still liquid. What is the reason?

  1. Ice is a bad conductor of heat.

  2. Since the surface of the lake is at the same temperature as the air, no heat is lost.

  3. The density of water is maximum at 4oC.

  4. None of the statements (1), (2) and (3) given above is correct.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Suppose temperature of water falling from 10 to 0 degree centigrade. When temperature of water falls upto 4 0 C, density of water will be maximum and water start sinking. Further temperature fall from 4 0C to 0 0C, density of water decreases continuously. In such condition water dose not sink and converted into ice and float on surface of water. At the same time 4 degree centigrade of temperature of interior water is maintained because ice is bad conductor of heat.

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