A wooden block is floating on water at `0^(@)C` keeping a portion V of its volume outside water. If the temperature of the water is increased from `0^(@)C` to `20^(@)C`, then what change of V will be observed?

Explanation

The density of water increases with the increase in temperature from `0^(@)C` to `4^(@)C`. With the increase in density of water, the upthrust on the block will increase. As a result, the block will gradually move up in water, i.e., the value of V will increase.
During the rise in temperature from `4^(@)C` to `20^(@)C`, the density of water decreases and hence the upthrust on the block will decrease. As a result, the wooden block will gradually sink in water, i.e., the value of V will decrease.