The sublimation process is basically an endothermic process in which particles of the solid substance on absorbing heat directly turns into gaseous (Vapours) forms. Whereas, the change of vapours into a solid on cooling is exothermic and known as the deposition or desublimation process.
Most of the solid substance on heating at first turns into a liquid form, and then turn into vapours (gas). Similarly, the gas turns into a liquid, when we cool it down thereafter into a solid.
However, few solids have the behaviour to change directly into a gaseous state on heating. Similarly, vapours turn back into a solid substance when we cool them. They do not go through the liquid state.
The solid substance which is participating in the sublimation process is known as Sublime. Whereas a solid obtained by cooling the vapours of the solid is known as sublimate.
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Examples Of Sublimation and Deposition
Some popular examples that explain exothermic and endothermic characteristics of sublimation and deposition processes are:
- Ammonioum Chloride
- Solid Carbon dioxide: Dry Ice
In some small houses, naphthalene balls are used to protect clothes from mosquitoes. This you will find in the market in a closed packet. As soon as you open up the packet, after some minutes naphthalene balls disappear with no residue left behind. The reason -why they disappear? is that the solid form turns into gases. They undergo a sublimation process. The solid particles on receiving heat from the surroundings change themselves into gases form.
Solid Carbon dioxide: Dry Ice
Another good example is dry ice. It is also known as solid carbon dioxide. Have you seen famous singers live stage shows? They use dry ice to make stage shows more attractive and to create special effects to make everything more alluring.
What do the stage representers do? is– they heat up solid carbon dioxide that sublimes on heating to form carbon dioxide gas. When the solids are heated the particle starts moving so quickly, start striking with each other. There is a level where the force of attraction becomes negligible does turn into a gaseous form. There is no longer closely packed particles. So, the process is an endothermic process where particles get excited after absorbing heat.
Again, on cooling down the solid carbon dioxide. also known as dry ice, these particles slow down their movement so quickly and it becomes fixed and form solid. They become closely packed particles and is a great example of a deposition exothermic process in which particles loses their heat when cooling.
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