Question

 When carbon dioxide is passed through limewater, the lime water turns milky. This is a 
1. Physical change
2. Chemical reaction
3. Crystallization
4. Condensation

Answer 1

Correct Answer - Option 2 : Chemical reaction

The correct answer is Chemical reaction.

CONCEPT:

Chemical reaction	A change in which one or more new substance is formed is a chemical change. It is also called a chemical reaction. Example: Burning of magnesium ribbon
Physical change	A change in which the physical properties of a substance undergoes change is called a physical change. It is a temporary change and no new substances are formed. It is generally reversible. Example: Cutting of wood
Crystallization	It is the process of formation of a solid substance from its melted form or solution. In crystals atoms/molecules of a substance arrange themselves in a well defined three-dimensional lattice. It is used as a purification technique. Example: Salt formed from seawater

EXPLANATION:

• When carbon dioxide is passed through lime water, calcium carbonate is formed which turns lime water into milky
• CO₂ + Ca(OH)₂ → CaCO₃ + H₂O
• This is a chemical change/ chemical reaction because a new substance calcium carbonate is formed in this reaction.
• It is also a permanent change.