2. Separation by Sublimation
We have already studied the process of sublimation in the previous chapter. We know that the changing of a solid directly into vapours on heating, and of vapours into solid on cooling is called sublimation.The solid substance which undergoes sublimation is said to 'sublime'. The process of sublimation is used to separate those substances from a mixture which sublime on heating. The solid substance obtained by cooling the vapours is known as 'sublimate'. The substances like ammonium chloride, iodine, camphor,naphthalene and anthracene sublime on heating and can be recovered in the form of a sublimate by cooling their vapours. This means that ammonium chloride,iodine, camphor, naphthalene and anthracene change directly from solid to vapours on heating, and from vapours to solid on cooling.
Most of the solid substances do not undergo sublimation.For example, substances such as common salt (sodium chloride), sand, iron filings, sulphur and chalk, etc., do not sublime on heating. The process of sublimation is used to separate that component of a solid-solid mixture which sublimes on heating (the other component of the mixture being non-volatile). Thus,ammonium chloride,iodine, camphor,naphthalene and anthracene can be separated from a mixture by sublimation. This will become more clear from the following example.
Notes
Matter in Our Surroundings - Notes
3. 7. Metals are Solids at the Room Temperature
Show Notes
4. 3. Non-Metals are Bad Conductors of Heat and Electricity.
Show Notes
5. 11. Non-Metals Have Many Different Colours.
Show Notes
10. 7. Non-Metals may be Solid, Liquid or Gases at the Room Temperature.
Show Notes
16. 8. Non-Metals Have Comparatively Low Melting Points and Boiling Points
Show Notes
18. 8. Metals Generally Have High Melting Points and Boiling Points.
Show Notes
24. To Study the Properties of a Suspension
Show Notes
25. Pure Substances : Elements and Compounds
Show Notes
28. Effect of Temperature and Pressure on Solubility
Show Notes
29. 1. Non-Metals are Not Malleable. Non-Metals are Brittle.
Show Notes
34. 1. Separation by Fractional Distillation
Show Notes
35. To Study the Properties of a Solution
Show Notes
36. Chemical Formula for daily use material
Show Notes
38. 6. Metals are Usually Strong. They Have High Tensile Strength.
Show Notes
39. 4. Non-Metals are Not Lustrous (Not Shiny). They are Dull in Appearance.
Show Notes
40. Separation of Mixture Of Two Solids
Show Notes
41. Separation Of Mixture Of a Solid And a Liquids
Show Notes
42. To Separate the Salt-Water Mixture (or Salt-Solution)
Show Notes
43. 2. Separation by a Separating Funnel
Show Notes
45. 11. Metals Usually Have a Silver or Grey Colour
Show Notes
49. Solutions, Suspensions And Colloids
Show Notes