Page 149 - August 2021

Subject: Chemistry
Topic: Sublimation
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Date: 1 August 2021
Activity: Demonstration of sublimation
We all would have observed the reduction in the size of naphthalene balls over time, vaporizing
of camphor upon burning, etc. The students were asked to ponder over the reason for this
phenomena observed and were also asked to relate the above mentioned phenomena to an
activity explained below:

A mixture of sodium chloride, sand and ammonium chloride was taken in a china dish. A funnel
in inverted position was placed over this china dish and the opening of the funnel was plugged
with cotton. This setup was then kept over Bunsen burner to expose it to flames. White fumes
could be observed and later white deposition could be seen on the underside of funnel. Upon
observing the left over contents in china dish, sand and sodium chloride was seen to be left
behind. Based on the observation, students concluded, ammonium chloride salts directly
converted into the vapour state and upon striking the cooler surfaces of funnel the vapours of
ammonium chloride solidified.
In all the above examples, there is a phase change but the solid is not passing into the
intermediate liquid stage. This process of direct conversion of solid state into vapour state is
called sublimation.
In life too, some experiences and situations exceeds the ordinary limits and take us beyond our
individual capacities. In this realm of sublime experience, one finds enlightenment.