Question

Which of the following are chemical changes? (i) Decaying of wood (ii) Burning of wood (iii) Sawing of wood (iv) Hammering of a nail into a piece of wood

• A. (i) and (ii)
• B. (ii) and (iii)
• C. (iii) and (iv)
• D. (i) and (iv)

Answer 1

The correct option is A

(i) and (ii)

Explanation for the correct options:
(A) (i) and (ii)

• If wood is deteriorated and burned, its chemical makeup will alter.
• Hence, decaying of wood and burning of wood are chemical changes.
• It cannot be returned to its previous state.
• The chemical makeup of compounds is not altered through physical activities.

Explanation for the incorrect option:

(B) (ii) and (iii)

• Sawing of wood is a physical change.
• Burning wood is a chemical transformation.

(C) (iii) and (iv)

• Wood is physically processed when it is sawed.
• When nails are driven into a piece of wood.
• This does not alter the chemical makeup of the components.

(D) (i) and (iv)

• Decaying of wood involves chemical changes because new chemicals are created and the chemical makeup of the wood is altered.
• Due to the nature of chemical reactions, which are irreversible.
• These modifications are permanent and cannot be changed back to their original state.
• Although driving a nail into a piece of wood requires physical effort.

Therefore, the correct option is (A) (i) and (ii).