Question

In a pressure-kerosene stove,
(i) We pump kerosene and convert it into vapours.
(ii) The vapours are then ignited.
Which of the following is true about the above statements?

• A. (i) is a chemical change; (ii) is a physical change.
• B. (i) is a physical change; (ii) is a chemical change.
• C. Both (i) and (ii) are physical changes.
• D. Both (i) and (ii) are chemical changes.

Answer 1

The correct option is B (i) is a physical change; (ii) is a chemical change.

Physical change: Pump kerosene and convert it into vapours

Chemical change: Vapours are then ignited

$\text{Explanation:}$ In pressure-kerosene stove, while pumping kerosene and converting it into vapours involve change in physical state only. No new substance is formed. So it is physical change.

During ignition of vapours, a lot of heat is evolved and new substance are formed leads to chemical change.