The metal M reacts vigorously with water to form a solution S and a gas G. The solution S turns red litmus to blue whereas gas G, which is lighter than air, burns with a pop sound. Metal M has a low melting point and it is used as a coolant in nuclear reactors. (a) What is metal M? (b) What is solution S? Is it acidic or alkaline? (c) What is gas G? (d) Write a balanced chemical equation for the reaction which takes place when metal M reacts with water. Is this reaction exothermic or endothermic?