Question

Sodium starts floating on water liberating hydrogen gas why

Answer 1

Sodium reacts violently with water. The effect is fascinating.

When sodium metal is first placed into water, it floats. But it immediately begins to react with water, releasing hydrogen gas:

A great deal of energy is released in this reaction. It is enough to set fire to the hydrogen gas. The sodium metal reacts with water. So much heat is released that the sodium melts. It turns into a tiny ball of liquid sodium. At the same time, the sodium releases hydrogen from water. The hydrogen gas catches fire and causes the ball of sodium to go sizzling across the surface of the water.