Question

Which of the following undergo sublimation?
A. Iodine crystals
B. Camphor
C. Naphthalene balls
D. All of the above

Answer 1

Hint: Consider the meaning of sublimation and what the process entails. Draw conclusions based on everyday laboratory experiences. Also, consider the vapour pressures of the substances.

Complete step by step solution:
Sublimation involves the change of state of a substance from the solid phase directly to the gas phase. All the substances that undergo sublimation have an appreciable vapour pressure at standard temperature and pressure.
These substances obtain enough energy from the environment to overcome the intermolecular bonds in the solid phase and directly escape into the vapour phase. The energy required to go from the solid phase to the vapour phase directly is known as the enthalpy of sublimation. The value for this can be obtained by adding the enthalpy of fusion and the enthalpy of vaporization.
Since sublimation requires energy from its surrounding to overcome the intermolecular hydrogen bonds, this is an endothermic process (absorbs heat from the surroundings).
We know that all the substances given in the options undergo sublimation. We have seen sublimation of iodine crystals in the laboratory and the sublimation of camphor and naphthalene balls in everyday life.

Hence, the correct answer to this question is ‘D. All of the above’

Note: Remember that sublimation is a purely physical process and the composition of the substances does not change on the molecular level. Sublimation of camphor is different than the burning of camphor when it is used as a fuel. When we burn camphor or even candles made of paraffin wax, they undergo a chemical change while reaction with oxygen. If camphor is left out in the air, it sublimates while paraffin wax does not. So, camphor is considered a sublimating substance.