The correct option is (c) 1 and 3 only.
Explanation
Changes in matter are broadly classified into physical and chemical changes. A physical change alters physical properties (such as shape, size, or state) without changing the chemical composition, whereas a chemical change results in the formation of new substances with distinct chemical properties.- Statement 1 is correct: Burning of paper is a combustion process in which the material reacts with oxygen to form new substances, such as carbon dioxide, water vapor, and ash. Since the chemical composition changes and the process is irreversible, it is a chemical change.
- Statement 2 is incorrect: Tearing of paper alters only the size and shape of the sheet. The chemical composition of the paper (cellulose) remains unchanged, and no new substance is formed. Therefore, it is a physical change.
- Statement 3 is correct: Folding of paper changes its physical appearance and shape. The paper can be unfolded to return to its original state (reversible), and its chemical nature remains intact. Thus, it is a reversible physical change.
Key Takeaway: The definitive characteristic of a chemical change is the formation of new substances (chemical reaction), whereas physical changes only affect the form or state of matter without altering its internal composition.