Question

Which of the following is not a chemical change?

• A. Rusting of iron
• B. Respiration
• C. Melting of wax
• D. Burning of wax

Hint:

Remember that "burning" almost always implies a chemical reaction (combustion), whereas "melting" or "boiling" denotes a physical change of state.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
A physical change alters the state or appearance but not the chemical composition.
A chemical change results in the formation of new substances with different chemical properties.

Step 2: Detailed Explanation:
Let's analyze the options:
(A) Rusting of iron forms a new compound (iron oxide), so it's a chemical change.
(B) Respiration breaks down glucose to form carbon dioxide and water, so it's a chemical change.
(C) Melting of wax only changes solid wax to liquid wax. The chemical composition remains the same. It is a physical change.
(D) Burning of wax reacts wax with oxygen to produce carbon dioxide and water vapor, so it's a chemical change.

Step 3: Final Answer:
Melting of wax is a physical change, not a chemical change.