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.
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Matter in Our Surroundings - Notes
2. 7. Metals are Solids at the Room Temperature
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5. 3. Non-Metals are Bad Conductors of Heat and Electricity.
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8. 11. Non-Metals Have Many Different Colours.
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9. 7. Non-Metals may be Solid, Liquid or Gases at the Room Temperature.
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15. 8. Metals Generally Have High Melting Points and Boiling Points.
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19. 8. Non-Metals Have Comparatively Low Melting Points and Boiling Points
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23. Chemical Formula for daily use material
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24. To Study the Properties of a Suspension
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25. Effect of Temperature and Pressure on Solubility
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26. 1. Non-Metals are Not Malleable. Non-Metals are Brittle.
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30. Pure Substances : Elements and Compounds
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31. Solutions, Suspensions And Colloids
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36. 1. Separation by a Suitable Solvent
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38. 4. Non-Metals are Not Lustrous (Not Shiny). They are Dull in Appearance.
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42. 3. Metals are Good Conductors of Heat and Electricity.
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46. 1. Separation by Fractional Distillation
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47. 6. Metals are Usually Strong. They Have High Tensile Strength.
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