Question

Which of the following is not a physical change?
(a) Boiling of water to give water vapour
(b) Melting of ice to give water
(c) Dissolution of salt in water
(d) Combustion of Liquefied Petroleum Gas (LPG)

NCERT Class X
Science - Exemplar Problems

Chapter_Chemical Reactions And Equations

Answer 1

(d) Combustion of Liquefied Petroleum Gas (LPG) - this is not a physical change , it is a chemical change as once it is burnt , the smoke particle cannot be changed  into Liquefied Petroleum Gas again.

Answer 2

Answer : The correct option is, (d) Combustion of Liquefied Petroleum Gas (LPG)

Explanation :

Chemical change : It is defined as the change in which the changes occurs in the chemical composition and thus resulting in the formation of new compound or substance. It is an irreversible reaction.

Physical change : It is defined as the change in which shape and size of a substance changes. In this there is no change in the chemical composition of the substance and no new substance is forming, only phase changes. It is a reversible reaction.

(a) Boiling of water to give water vapor : It is a physical change because there is changes in the phase from liquid state to gaseous state.

(b) Melting of ice to give water : It is a physical change because there is changes in the phase from solid state to liquid state.

(c) Dissolution of salt in water : It is a physical change because there is no change in the chemical composition of the substance and no new substance is forming.

(d) Combustion of Liquefied Petroleum Gas (LPG) : It is a chemical change because in this process, chemical reaction takes place that means changes occurs in the chemical composition and new compound is formed by the combustion.

Hence, the correct option is, (d) Combustion of Liquefied Petroleum Gas (LPG)