Select the metal that does not react with cold water but reacts with steam when heated is:
A. Copper
B. Sodium
C. Zinc
D. Magnesium

Hint: It is a chemically active element and marked as the most abundant element in the eighth position. It is highly rich in green leafy vegetables and grains. On heating, this element gives bright light which is helpful for the photographers to click images at dark.

Complete step by step answer:
The element copper is located just below the element hydrogen in the periodic table. Therefore, it
cannot carry out hydrogen from the water.
Due to this, the element copper does not react with cold water as well as steam.
The element sodium is highly reactive with water. It reacts with cold water to form a base by releasing
hydrogen gas.
$2Na(s) + 2{H_2}O(l) \to 2NaOH(aq) + {H_2}(g)$
Sodium metal reacts with steam to form sodium oxide and hydrogen gas.
The reaction is shown below
$2Na(s) + {H_2}O(g) \to N{a_2}O(s) + {H_2}(g)$
The metal zinc does not react with cold water as on coming in contact with the water it creates a
protective layer of zinc hydroxide.
The reaction is shown below
$Zn(s) + 2{H_2}O(I) \to Zn{(OH)_2}(s) + {H_2}(g)$
Zinc slowly reacts with steam to form zinc oxide and releases hydrogen gas.
The reaction is shown below.
$Zn(s) + {H_2}O(l) \to ZnO(s) + {H_2}(g)$
The metal magnesium is slightly reactive when it reacts with cold water. As soon it’s come in contact
with the water it creates a layer of magnesium hydroxide which enables it to further react with water.
The reaction is shown below.
$Mg(s) + 2{H_2}O(I) \to Mg{(OH)_2}(s) + {H_2}(g)$
When magnesium is reacted with steam and heated, it burns to form white magnesium oxide with the
release of hydrogen gas.
The reaction is shown below.
$Mg(s) + {H_2}O(g) \to MgO(s) + {H_2}(g)$
Thus, the metal which does not react with cold water but reacts with steam in heating is magnesium.
Therefore, the correct option is D.

Note:
The metal sodium and potassium are vigorously reactive. In coming in contact with water or oxygen can be explosive and cause severe damages. To avoid the consequences, sodium is immersed in kerosene as it is not reactive with kerosene.