Question

Why does calcium start floating when water is added to.water

Answer 1

calcium is one of the hardest metal found in nature and it is insoluble in water so when it is mixed with water instead of reacting with water it floats

Answer 2

the reaction of calcium with water is less violent , so the heat released is not sufficient for the hydrogen to catch fire . calcium starts floating because the bubbles of hydrogen gas which are from during the reaction stick to the surface of the metal and hence calcium floats on water