Question

Which of the following is a chemical change?
A.Explosion of dynamite
B.Sublimation of iodine
C.Melting of sodium in a nuclear reactor
D.Condensation of steam

Answer 1

Hint: If a substance is reacted with another substance, there is a formation of a new chemical compound or chemical substance and this process is known as chemical decomposition or chemical synthesis. The properties of both reactants may be different and the molecular composition of reactants will completely change with change in the energy of the substance.

Complete answer:
Among these options, an explosion of dynamite is caused by a chemical change. Because the explosion process is a chemical reaction and it is an exothermic reaction. The dynamite is made up of nitroglycerin, sorbents and stabilizers and dynamite is an explosive material.
When the dynamite explodes, a chemical changes. The dynamite is mainly composed of carbon, oxygen and nitrogen and when it explodes, there is a formation of some covalent gases like carbon dioxide, and carbon monoxide etc. and it is very stable. While the explosion of dynamite, it releases more energy. Therefore, we can say that, Explosion of dynamite is a chemical change. Hence, option (A) is correct.
Sublimation of iodine is not a chemical process. Because, it occurs by a change of states. Therefore, it is a physical process. Hence, the option (B) is incorrect.
Melting process is not a chemical change. Because, it is a physical process. Here, the change occurs in only the properties of substance. Hence, option (C) is incorrect.
Condensation of steam occurs by physical change. Here, the vapours are transformed into liquid states. Therefore, condensation of steam is not a chemical change. Hence, the option (D) is incorrect.

Note:
Among these options, the explosion of dynamite is a chemical change. Because, here by the explosion of some molecules like carbon, oxygen and nitrogen there is a formation of covalent gases like carbon dioxide, and carbon monoxide. And by this explosion, there is a release of a high amount of energy. An explosion of dynamite is an exothermic reaction.