The correct option is (a).
Explanation
Changes in matter are broadly classified into physical and chemical changes. This classification depends on whether the chemical identity and composition of the substance remain unchanged (physical) or are altered to form new substances (chemical).
Statement 1 is Correct:
The interconversion of states of matter (such as melting, freezing, or boiling) is a physical change. During these transitions, the physical state of the substance changes (e.g., from solid ice to liquid water), but the chemical identity remains identical (H2O). No chemical bonds are broken or formed to create a different compound.
Statement 2 is Incorrect:
Physical changes do not involve a change in the chemical composition of the substance. They only affect physical properties like shape, size, state, or color. A change in chemical composition is the defining characteristic of a chemical change.
Statement 3 is Incorrect:
Physical changes do not result in the formation of new substances. The substance retains its original chemical nature. The formation of new substances with distinct properties occurs only during chemical changes.
Key Takeaway:
Physical changes are reversible transformations affecting only the physical properties of a substance without altering its chemical composition or creating new substances.