Question

Dry ice is an example of ______ process.
A.Evaporation
B.Crystallization
C.Sublimation
D.Purification

Answer 1

Dry ice is solid carbon dioxide. The state in which carbon dioxide generally exists is gas. Consider the conversion process of gas to solid.

Complete step by step answer:
Let us look at each of the options one by one:
Evaporation: Evaporation is a process in which liquid gets converted into vapours. It may be natural or we may need to give extra energy to precede reaction. But carbon dioxide is a gas and it is converted to solid state. So, no role of evaporation seems here.
Crystallization: This is the process of formation of solids. The solid is formed by crystallizing the liquid solution of that solid. Here, there is no involvement of gas.
Sublimation: Sublimation is a process of conversion of gas into solid. This process perfectly suits the given condition as carbon dioxide is a gas and dry ice is in solid state.
Since dry ice gets directly converted into carbon dioxide gas, it is a sublimation process.
Purification: Let us look at purification too. This is a process of removing impurities from a given sample. There are many methods of purification such as re-crystallization, distillation and sublimation.

The correct answer is option C.

Note:
Dry ice is a very good cooling agent. It is very dangerous to handle and toxic. One should not use it without protecting gears. It does not leave any residue and provides a much cooler temperature than water. It sublimes at ${\text{194}}{\text{.65 K}}$.