Question

Calcium starts floating when water is added to it. Give reason.

Answer 1

Calcium reacts with water and forms Calcium hydroxide ($Ca{\left(OH\right)}_2$) and Hydrogen ($H_2$) as products at room temperature.

Calcium ($Ca$) starts floating on the water because the bubbles of Hydrogen ($H_2$) gas which are formed during the reaction gets stick to the surface of the metal and makes the Calcium ($Ca$) metal to float on water.

The chemical reaction of Calcium ($Ca$) with Water ($H_{2}O$) is as follows.

$\underset{Calcium}{Ca\left(s\right)}+\underset{Water}{2H_{2}O\left(l\right)}\to \underset{Calciumhydroxide}{Ca{\left(OH\right)}_2\left(aq\right)}+\underset{Hydrogen}{H_2\left(g\right)}$