Question

The top of a lake is frozen when the air in contact with the lake surface is at $-5^{0}C$. The temperature of water in contact with the bottom of the lake will be

• A. $-5^{0}C$
• B. $4^{0}C$
• C. $0^{0}C$
• D. $-4^{0}C$

Answer 1

Answer: (B)

$4^{0}C$

Water will attain its maximum density at $4^{o}C$ (277 K) and hence its mass will be maximum at this temperature. Ice being lighter will float on surface of water. This is the reason why temperature at the bottom of all the frozen lakes and oceans is constantly $4^{o}C$ (277 K).