Question

Describe an activity to demonstrate sublimation of Ammonium chloride.

Answer 1

Hint: Heating of salt like ammonium chloride shows sublimation. With the help of a burner and a setup which does not allow the formed vapour to escape will demonstrate sublimation of ammonium chloride salt.

Complete Answer:
Matter exists in three forms namely solid, liquid and gas. The state of a given matter can be changed with the change in temperature and pressure. Interconversion of the three states of matter is as follow:

FROM	TO	Process
Solid	liquid	Fusion
Solid	Gas	Sublimation
Liquid	Solid	Solidification
Liquid	Gas	Vaporisation
Gas	Solid	Desublimation
Gas	Liquid	Condensation

As sublimation is the process of converting the solid state of a matter directly into its vapour state. In sublimation, no liquid state is observed. This is a reversible process which means substances whose solid are converted into vapour, these vapours can also directly change into solid. Some substances which show sublimation process are as follows Camphor, Naphthalene, Anthracene and Ammonium chloride.
An activity to demonstrate sublimation of compounds like ammonium chloride requires china dish, funnel, cotton, burner and ammonium chloride salt. Procedure for this activity is to take some ammonium chloride salt in a china dish, gently crushing the salt taken. Now put a funnel upside down or inverted funnel over the china dish with its broad face covering the china dish and its stem at top. Now close the opening of the stem of the funnel using a cotton plug. Put this setup over the burner and start heating the china dish slowly. The observation of this activity is that salt of ammonium chloride undergoes sublimation as the solid crystals of ammonium chloride directly changes to its gaseous state on heating and also no liquid state is observed.
Thus, through this activity we can demonstrate sublimation of Ammonium chloride.

Note: Sublimation is an endothermic process. Reverse of sublimation or change of vapor state directly to solid state is known as deposition. Sublimation is a physical process, not a chemical reaction.