Answer: Option (1) is the correct answer.
Step-by-step explanation:
Chemical changes are defined as the changes which tend to show difference in chemical composition of a substance.
For example, toxicity, reactivity, combustion etc are all chemical changes.
In a chemical change, there will always be formation of a new compound.
On the other hand, a change which is unable to bring any difference in chemical composition of a substance is known as a physical change.
For example, a change in shape, size, mass, volume etc are all physical changes.
Thus, we can conclude that when one substance changes into one or more new substances, it has exhibited a chemical change.