NEET Physics: States of Matter questions with solutions

Q1. Which phenomenon occurs during the following change? Size of naphtalene balls decreases.

1. condensation
2. sublimation
3. evaporation
4. melting

Answer: sublimation

Naphthalene balls shrink because the solid changes directly into vapor at room temperature. Since no liquid stage is involved, this is sublimation.

Q2. Sublimation is a technique that helps chemists to:

1. break
2. purify
3. melt
4. freeze

Answer: purify

Sublimation is useful for purification because a sublimable solid changes directly from solid to gas and then re-deposits as a cleaner solid. Impurities that do not sublime stay behind, so the sample becomes purer.