Question

Changing of solid directly into the gaseous state is called

• A. Melting
• B. Boiling
• C. Evaporation
• D. Sublimation

Answer 1

The correct option is D

Sublimation

Explanation for Correct option :

Option(D):

• Changing of solid directly into a gaseous state without passing into the liquid state is called Sublimation.
• The process of sublimation can be used to purify the impure samples of substances.
• The non-volatile impurities which are present in the impure sample will not change into vapours and remains in the dish.
• Example: Naphthalene, camphor, Iodine etc.

Explanation for incorrect option :

Option (A) :

• The temperature at which a solid substance melts and changes into a liquid at atmospheric pressure is known as the melting point of the solid.
• The melting point of a substance helps to predict the magnitude of inter-particle forces of attraction between its particles.
• More the melting point, the stronger the force of attraction.

Option (B) :

• The temperature, at which a liquid boils and changes rapidly into a gas at a given atmospheric pressure, is called the boiling point of the liquid.
• When the forces of intermolecular attractions are greater, the boiling point of the liquid will be more.

Option(C) :

• The process of changing the liquid state into a vapour state even below its boiling point is known as evaporation.
• The process of evaporation is a surface phenomenon which means that only those particles of the liquid change into vapours which are present on its surface.

Thus, Option D is the correct option.