Question

Which of the following is not a physical change?
A. Boiling water to give water vapor
B. Melting of ice to give water
C. Dissolution of salt in water
D. Combustion of Liquefied Petroleum Gas (LPG)

Answer 1

Hint: Physical change alters the form of a substance, but do not change it to another substance. It changes shape or size. It dissolves. It changes phase. When a substance undergoes a chemical change, it is changed into a different substance with different properties.

Complete step by step answer:
Matter is anything that has space and mass. Matter is always experiencing both physical as well as chemical change.
Chemical changes are changes matter undergoes when it becomes new or different matter. Temperature changes without heating or cooling. It bubbles, burns, changes color and forms a precipitate. E.g. Precipitation, color change, gas production etc. A chemical change occurs when fireworks are used. They are made up of magnesium and copper. These change chemically as they light up the sky.
Physical change occurs when matter changes its property but not its chemical nature. Physical property changes could include a change in texture, shape, size color, odor, volume, weight and density. E.g. A boiled egg. No new substances are formed. It involves very little absorption of energy.
Boiling water to give vapor is a physical change because it is reversible. The water vapor can be cooled to give water. Melting of ice to give water is also a physical change. There is a change in the phase of the matter. Dissolution of salt in water does not produce any new substance. Moreover it is reversible too. But combustion of LPG produces new substances. Thus it is a chemical change.


So, the correct answer is Option D.

Note:

Physical changes	Chemical changes
Reversible	Irreversible
Temporary	Permanent
Undergoes physical change	Undergoes chemical change
Affects only physical properties	Affects chemical properties
Do not involve energy production	Involve energy production