Explain why calcium metal after reacting with water starts floating on its surface. write the chemical equation for this reaction. name one more metal that starts floating after sometime then floats with water.

Firstly, the chemical equation between the calcium metal and water will be:  

Ca(s) + 2 H₂O(l) → Ca(OH)₂(aq) + H₂(g)  

We can see from the equation the bubbles of hydrogen gas which are formed during the reaction stick to the surface of the metal and hence calcium floats on water.  

The other metal that will float on the water during the reaction is magnesium which have the same chemical behavior like calcium, we can illustrate that by the chemical equation:

Mg(s) + 2 H₂O(l) → Mg(OH)₂(aq) + H₂(g)

the answer is true.