Q: The heat required to melt 2 kg of ice at 0 °C (latent heat of fusion of ice = 336000 J/kg) is:

672000 J. Heat Q = mL = 2 \times 336000 = 672000 J.

Question 1

The direct change of a solid into a gas without passing through the liquid state is called:

Accepted Answer

sublimation. Sublimation is the solid-to-gas transition (e.g. camphor, dry ice).

Question 2

Which of the following substances undergoes sublimation?

Accepted Answer

Camphor. Camphor (like naphthalene and dry ice) sublimes directly from solid to vapour.

Question 3

The heat energy absorbed by a solid at its melting point to change into a liquid, without any rise in temperature, is called the:

Accepted Answer

latent heat of fusion. Latent heat of fusion is absorbed at constant temperature to convert solid to liquid.

Question 4

Evaporation of sweat cools our body because evaporation:

Accepted Answer

absorbs latent heat from the body. Evaporating sweat takes latent heat of vaporisation from the skin, producing a cooling effect.

Question 5

During the melting of ice, the temperature of the ice–water mixture remains at 0 °C because the heat supplied is used to:

Accepted Answer

overcome the forces holding the solid particles together (latent heat). The absorbed latent heat breaks the bonds of the solid rather than raising the temperature.

Question 6

The heat required to melt 2 kg of ice at 0 °C (latent heat of fusion of ice = 336000 J/kg) is:

Accepted Answer

672000 J. Heat Q = mL = 2 	imes 336000 = 672000 J.

Phase Changes & Latent Heat — Homi Bhabha Exam Chemistry MCQs with Solutions

Questions with solutions