Asked by Praveen Kumar | 2nd May, 2014, 08:08: PM

Expert Answer:

The temperature at the bottom of a lake whose upper surface has frozen to ice would be around 4 degrees centigrade (option c). This is because as the water cools to this temperature it reaches its maximum density so will tend to drop to the bottom of the lake. The water above may then cool further & freeze, but this 'heavy' layer will stay at the bottom, insulated by the layers of water above. This is essential to the survival of fish etc, as otherwise in cold weather ponds/lakes could freeze completely.

Answered by  | 5th May, 2014, 11:21: AM

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