How can we make model of sublimation .. ( Working) ..
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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 (cold finger), leaving a non-volatile residue of impurities behind.There are many examples of sublimation in daily life: The air fresheners used in toilets. The solid slowly sublimes and releases the pleasant smell in the toilet over a certain period of time. Moth balls, made of naphthalene are used to drive away moths and some other insects.
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Sublimation
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Bucket of dry ice pellets going through sublimation
Instants/Getty Images
by
Andrew Zimmerman Jones
Updated January 27, 2019
Sublimation is the term for when matter undergoes a phase transition directly from a solid to gaseous form, or vapor, without passing through the more common liquid phase between the two. It is a specific case of vaporization. Sublimation refers to physical changes of transition, and not to cases where solids convert into gas due to a chemical reaction. Because the physical change from a solid into a gas requires the addition of energy into the substance, it is an example of an endothermic change.
How Sublimation Works
Phase transitions are dependent upon the temperature and pressure of the material in question. Under normal conditions, as generally described by kinetic theory, adding heat causes the atoms within a solid to gain energy and become less tightly bound to each other. Depending on the physical structure, this usually causes the solid to melt into liquid form.
If you look at the phase diagrams, which is a graph that depicts the states of matter for various pressures and volumes. The "triple point" on this diagram represents the minimum pressure for which the substance can take on the liquid phase. Below that pressure, when the temperature drops below the level of the solid phase, it transitions directly into the gas phase.
The consequence of this is that if the triple point is at high pressure, as in the case of solid carbon dioxide (or dry ice), then sublimation is actually easier than melting the substance since the high pressures needed to turn them into liquids are typically a challenge to create.
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