Which of the following is an example of a physical change? In this example, there is no change in chemical composition of matter.
A: Coal changing into coal ash on burning
B: Preparing a sweet drink by mixing sugar in water
C: White washing walls using a solution of lime and water
D: Mixing salt and lemon juice in a beaker
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. only B.
Preparing a sweet drink by mixing sugar in water is a physical change because it involves no alteration in the chemical composition of the substances involved. The sugar dissolves in water, forming a homogeneous mixture, but both sugar and water retain their original chemical identities. This process is reversible—the sugar can be recovered by evaporating the water. Physical changes are characterized by changes in state or form without forming new substances, and this example fits that definition perfectly.
Other options :
- A: Coal changing into coal ash on burning: This is a chemical change involving combustion, which produces new substances like ash, gases, and heat.
- C: White washing walls using lime and water: This is a chemical change; lime (Ca(OH)₂) reacts with CO₂ in the air to form CaCO₃ (calcium carbonate).
- D: Mixing salt and lemon juice in a beaker: This involves chemical reactions, such as acid-base reactions between citric acid and salt, forming new substances.