Question

The temperature of water at the surface of a deep lake is $2^{\circ }C$. The temperature expected at the bottom is

• A. $2^{\circ }$
• B. $0^{\circ }$
• C. $4^{\circ }$
• D. $-6^{\circ }$

Answer 1

Answer: (C)

Water exhibits an anomalous behaviour; it contracts on heating between $0^{o}C$ and $4^{o}C$. When the surface of the lake cools down above $4^{o}C$ the cool water at the surface flows to the bottom because of its greater density. But when the surface temperature reaches to $2^{o}C$, the water near the surface is less dense than the warmer water below. Hence the downword flow ceases, and the water near the surface remains colder than that at the bottom.
So the temperature expected at the bottom is $4^{o}C$
option (C) is the correct answer.