The surface of a lake is frozen in severe winter, but the water at its bottom is still liquid. What is reason?
[UPSC Civil Services Exam – 2011 Prelims]
(a) Ice is a bad conductor of heat.
(b) Since the surface of the lake is at the same temperature as the air, no heat is lost.
(c) The density of water is Maximum at 4 degree Celsius.
(d) None of the above
Answer: (c)
Explanation:
- During severe winter, lakes may experience surface freezing while the water at the bottom remains liquid due to the anomalous expansion of water.
- This is because water reaches its maximum density at 4 degrees Celsius and starts expanding as the temperature continues to drop below this point.
- As a result, when water freezes, it becomes less dense and floats to the surface, allowing the colder liquid water to remain below the layer of ice.
