Question

During severe winters in the temperate zone of the world, the superficial parts of the lake are frozen, leaving water below. Then the freezing at the bottom is mainly prevented because

• A. the conductivity of ice is low.
• B. the water has large latent heat of fusion.
• C. the water has large specific heat.
• D. the temperature of the earth at the bottom of the lake is high.

Answer 1

Answer: (A)

the conductivity of ice is low.

The concepts involved in this complicated phenomena are low conductivity of ice and anomalous expansion of water (water density is highest at $4^{o}C$).
When initially, the top layer of ice is formed on account of high exposure to low temperature, this ice sheet cuts off heat transfer from water (high temperature) to air (low temperature) on account of low conductivity.