CBQ - Burning of candle — task. Physics CBSE Live product, Class 7 (2026-27).

Read the following case and answer the following questions:

A student lights a candle during a power cut. After a few minutes, she notices that the solid wax near the flame melts into liquid wax. The liquid wax is then heated further and changes into wax vapour, which burns in the presence of oxygen to produce heat and light. After the candle is blown out, the melted wax cools and becomes solid again. The student concludes that different types of changes are taking place during the burning of a candle.

Read the case carefully and answer the following questions.

1. Which of the following is the chemical change taking place during the burning of a candle?

Burning of wax vapour in the presence of oxygen
Change in the shape of the candle
Melting of wax
Solidification of wax after cooling

2. Why is the burning of candle wax considered an irreversible chemical change?

Because the wax becomes soft.
Because the wax melts.
Because the wax changes its shape.
Because new substances are formed and the original wax cannot be obtained back.

3. Which statement best explains why a burning candle involves both physical and chemical changes?

Only burning takes place.
Only melting takes place.
The wax melts (physical change) and the wax vapour burns to form new substances (chemical change).
Only the wick burns.

4. Which observation provides the strongest evidence that burning of wax is a chemical change?

The wax becomes liquid.
New substances such as carbon dioxide and water vapour are produced.
The candle changes shape.
The wax becomes soft.

8. CBQ - Burning of candle

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