Solution:
Concept- A change can be categorised as a chemical or physical change depending on how the properties of the subject change when it undergoes the change.A substance is said to undergo a physical change when only physical properties such as shape, size, colour, state or appearance of a substance change. Its chemical composition remains intact. Some characteristics of physical change are:
● Temporary change.
● It does not affect the internal structure of the substance, only the molecules are rearranged.
● No new substance is formed.
● Most physical changes are reversible. We can get the fabric back even after the change.
A substance is said to undergo a chemical change when the chemical properties of the substance change. As a result, atomic bonds are either formed or broken at the molecular level. Some properties of chemical change are:
● Permanent change.
● As the original composition of a substance changes, one or more new substances are formed.
● Forms of energy such as heat, light or electricity can be emitted or absorbed.
● Chemical change is generally irreversible.
Hence, the correct answer is 3.
