Question

Which phenomenon occurs during the following change?
Size of naphthalene balls decreases.
A. condensation
B. sublimation
C. evaporation
D. melting

Answer 1

Hint: Sublimation is also a kind of transition of the phase or a variation in a state of matter as melting, freezing or evaporation. Sublimation is given as the change in the state of matter from solid to gas, directly. That means, the intermediate phase called liquid state is not present.

Complete step by step answer:
The process of sublimation is a physical change of state. This cannot be helpful in describing the change of state of matter from the solid to liquid in a chemical reaction. There are a lot of examples for this process. Dry ice is a common example for this. Sublimation is due to the absorption of heat which will give needed energy for certain molecules in order to overcome the forces of attraction due to their neighbour molecules and change into the vapour state directly. As we said, the process needs extra energy, this will be an endothermic process. The enthalpy of sublimation or the heat of sublimation is determined by summation of the enthalpy of fusion and the enthalpy of vaporization. Naphthalene is an organic compound which is generally used in pesticides such as mothballs. As it is made of non-polar molecules, which are held together only using the Van der Waals intermolecular forces. Because of this, they can sublime easily. Naphthalene sublimes at standard atmospheric temperature and pressure.

So, the correct answer is “Option B”.

Note:
Naphthalene balls are used with cloths and documents for the protection of these things from the insects. When the naphthalene balls undergo the process of sublimation under atmospheric temperature, the solid phase directly changes to vapour, which will be spread all over the things to be protected. This vapour will prevent it from the stay of insects in clothes and documents. This happens when it is kept in an open area.