Question

answer fast ⌛⌛⌛⌛⌛⌛⌛⌛⌛⌛⌛⌛⌛♋️⌛⌛⌛⌛⌛⌛⌛⌛⌛⌛⌛⌛

Answer 1

calcium starts floating in water because calcium reacts with water and hydrogen gas is liberated. This hydrogen gas Bubbles gets sticked to the metal which makes it to float on the surface of water

Answer 2

the reaction of calcium with water is very less violent ,..the heat evolved is not sufficient for the hydrogen to catch fire
calcium starts floating because the bubbles of hydrogen gas formed stick to the surface of the metal
the reaction of sodium and potassium is react vigoursly react with water