Question

name two metals which react vigorously even with cold water and one metal which,if ignited continues to burn in steam

Answer 1

Metals at the top of the reactivity series (Sodium potassium) react readily (violently) with cold water forming hydroxides with the liberation of H2, the heat evolved is sufficient for the hydrogen to catch fire.

Na(s) + 2H2O(l) → NaOH(aq) + H2(g) + large amount of heat energy
catches fire
K(s) + 2H2O(l) → KOH(aq) + H2(g) + large amount of heat energy
catches fire
Calcium being at the top of the reactivity series reacts with water to form calcium hydroxide and hydrogen gas. The reaction of calcium with water is less violent (compared to Na and K). The heat evolved is not sufficient for the hydrogen to catch fire.
Ca(s) + 2H2O(l) → Ca(OH)2(aq) + H2(g) + small amount of heat energy
does not catch fire

While other metals like Magnesium is less reactive towards cold water. It reacts very slowly with cold water. Few bubbles of H2 gas is produced.
Mg(s) + H2O(l) → Mg(OH)2(aq) + H2(g)
Very few bubbles of H2gas is produced
While Zn, Fe, has no reaction towards cold water but do react with steam forming metal oxides (still Pb, Cu, Ag do not react with steam).
Cold water
Zn, Fe, -----------> No reaction
Steam
Zn, Fe, -----------> Metal oxides
Steam
Pb, Cu, Ag -----------> No reaction.

Answer 2

Answer:

sodium and pottasium

magnesium