Which of the following metals float in water when it is reacted with cold water?
Calcium (Ca)
Different metals react with water differently.Some metals(like sodium ,potassium) react with cold water while some metals (like magnesium) requires steam i.e. hot water to react.
Metals react with water to give hydroxides and hydrogen gas.
Calcium reacts less vigorously with water to form hydrogen gas. The metal starts floating because the bubbles of hydrogen gas formed stick to the surface of the metal.