Give reasons.
$(i)$ Lakes freeze from top towards bottom.
$(ii)$ Ice floats on water.

(N/A) $(i)$ During winter,the temperature of lake water decreases. Since cold water is denser,it sinks to the bottom,while warmer water rises to the surface. This continues until the entire lake reaches $277 \ K$ $(4^{\circ}C)$. Below $277 \ K$,the surface water becomes less dense as it cools further,causing it to remain at the top and eventually freeze.
$(ii)$ The density of ice is lower than that of liquid water due to its open cage-like structure formed by hydrogen bonding,which causes it to float on water.