Consider the following statements regarding the burning of wood: 1. It involves the conversion of wood into new substances like ash and smoke. 2. It is a physical change. 3. It is an irreversible process. Which of the statements given above is/are correct?

The correct option is (c). Explanation Changes in matter are broadly classified into physical and chemical changes. A physical change affects only the physical properties (such as state, shape, or size) without altering the chemical composition. A chemical change involves a chemical reaction resulting in the formation of new substances with different chemical properties, and such changes are typically irreversible. Statement-wise Analysis: - Statement 1 is Correct: The burning of wood is a combustion reaction. During this process, the organic compounds in wood (primarily cellulose and lignin) react with oxygen to produce entirely new substances, including carbon dioxide, water vapour, ash, and smoke. - Statement 2 is Incorrect: Because the process involves a change in chemical composition and the formation of new substances, it is defined as a chemical change. A physical change would imply that the wood remains chemically the same, which is not the case here. - Statement 3 is Correct: The burning of wood is an irreversible process. Once the wood has been converted into ash and gaseous byproducts, it is impossible to reverse the reaction to recover the original wood. Key Takeaway: Combustion (burning) is a chemical change characterized by the formation of new substances (ash, gases) and the release of energy, distinguishing it from physical changes which are reversible and do not alter chemical identity.

NCERT Class 9 Science — Chapter 2: Is matter around us pure?

mcqeasy

Consider the following statements regarding the burning of wood:

It involves the conversion of wood into new substances like ash and smoke.
It is a physical change.
It is an irreversible process.

Which of the statements given above is/are correct?

Official previous-year question

Verified 1 Aug 2026.

Options

A1 and 2 only
B2 only
C1 and 3 only
D1, 2 and 3

Did you get this right?

Solution

The correct option is (c).

Explanation

Changes in matter are broadly classified into physical and chemical changes. A physical change affects only the physical properties (such as state, shape, or size) without altering the chemical composition. A chemical change involves a chemical reaction resulting in the formation of new substances with different chemical properties, and such changes are typically irreversible.

Statement-wise Analysis:

Statement 1 is Correct: The burning of wood is a combustion reaction. During this process, the organic compounds in wood (primarily cellulose and lignin) react with oxygen to produce entirely new substances, including carbon dioxide, water vapour, ash, and smoke.
Statement 2 is Incorrect: Because the process involves a change in chemical composition and the formation of new substances, it is defined as a chemical change. A physical change would imply that the wood remains chemically the same, which is not the case here.
Statement 3 is Correct: The burning of wood is an irreversible process. Once the wood has been converted into ash and gaseous byproducts, it is impossible to reverse the reaction to recover the original wood.

Key Takeaway:
Combustion (burning) is a chemical change characterized by the formation of new substances (ash, gases) and the release of energy, distinguishing it from physical changes which are reversible and do not alter chemical identity.

Your note

More from Chapter 2: Is matter around us pure?

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In the classification of colloids, 'Cheese' and 'Butter' are examples of:

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Consider the following statements about air: 1. It is a homogeneous mixture of gases. 2. Its two main constituents are carbon dioxide and argon. 3. It is considered a solution of gas in gas. Which of the statements given above is/are correct?

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The correct option is (c).

Explanation

Statement-wise Analysis:

Statement 1 is Correct: The burning of wood is a combustion reaction. During this process, the organic compounds in wood (primarily cellulose and lignin) react with oxygen to produce entirely new substances, including carbon dioxide, water vapour, ash, and smoke.
Statement 2 is Incorrect: Because the process involves a change in chemical composition and the formation of new substances, it is defined as a chemical change. A physical change would imply that the wood remains chemically the same, which is not the case here.
Statement 3 is Correct: The burning of wood is an irreversible process. Once the wood has been converted into ash and gaseous byproducts, it is impossible to reverse the reaction to recover the original wood.