Sublimation

Sublimation is a process in which solid is directly change into gas state without passing through liquid state. The substances which shows the process of sublimation are known as sublimate.
Examples of sublimate: Camphor, ammonium chloride, naphthalene etc.

Process: Sublimation is a technique used by chemists to purify compounds. A solid is typically placed in a

sublimation apparatus and heated under vacuum. Under this reduced pressure, the solid volatilizes and condenses as a purified compound on a cooled surface, leaving a non-volatile residue of impurities behind. Once heating ceases and the vacuum is removed, the purified compound may be collected from the cooling surface. 

Characteristics:

1. Sublimation is an endothermic process, i.e., heat is taken up from the surrounding for the phase transition.
2. Sublimation is a physical change and not a chemical change. For example, decomposition of ammonium chloride on heating to ammonia and hydrogen chloride is a chemical reaction and not sublimation. Also, combustion of hydrocarbons to carbon dioxide gas and water vapour is not sublimation.

Advantages:

1. Fast
2. Cheap

Disadvantages:

1. Non-sublimate compounds may decompose under heating.
2. Recovery may not be complete- the fumes may be blown away.