State the conditions under which the following metals react with water. Write the equation for each reaction:
$(a)$ $Na$
$(b)$ $Mg$
$(c)$ $Fe$

What is the melting point of sulfur (in $K$)?

$A$ metal $M$ forms an oxide having the formula $M_{2}O_{3}$. It dissolves in both dilute sulphuric acid and dilute sodium hydroxide solution. Identify the metal and write the chemical equations for the reactions involved.

Out of the two metals $P$ and $Q$, $P$ is less reactive than $Q$. Suggest an activity to arrange these metals in the order of their decreasing reactivity. Support your answer with a suitable chemical equation.

What is the chemical formula of rust?

$(a)$ $A$ substance $X$,an oxide of a metal,is used extensively in the cement industry. This element is found in our bones also. On treatment with water,it forms a solution which turns red litmus blue. Identify $X$ and also write the chemical reaction involved.
$(b)$ Choose a metal from the following metals which reacts only with hot water: Sodium,magnesium,iron. Mention the products formed during the reaction.