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  • FREE 5-MIN Notes
    • 1. Experimental Techniques
    • 2. Methods of Purification
    • 3. Separation Techniques
    • 4. Qualitative Analysis
    • 5. Kinetic Particle Theory
    • 6. Atomic Structure
    • 7. Elements, Compounds, Mixtures
    • 8. Ionic Bonding
    • 9. Covalent Bonding
    • 10. Mole Concept
    • 11. Electrolysis
    • 12. Energy Changes
    • 13. Speed of Reaction
    • 14. Redox
    • 15. Acids and Bases
    • 16. Salts
    • 17. Ammonia
    • 18. Periodic Table
    • 19. Metals
    • 20. Air
    • 21. Fuels
    • 22. Organic Chemistry
    • 23. Macromolecules
  • Free Printables

2. Methods of Purification

Determining purity
  • A pure substance is made up of only one substance and is not mixed with any other substance.
  • A mixture is a substance that contains two or more substances that are not chemically combined.

Pure substance: Has a fixed and constant melting & boiling point.
Impure substance:
  • Melting point is lower than that of the pure solid, melts over a range of temperature
  • Boiling point is higher than that of the pure liquid, boils over a range of temperature
 
How to determine whether a substance is pure?
  • By checking its melting and boiling point: Pure substances have fixed melting and boiling points.
  • By using chromatography

EXAM TIP: Only these 3 methods are allowed to determine purity. 

Effect of impurities on melting and boiling point
  • Cause melting and boiling to take place over a range of temperatures.
  •  Decrease melting point: The greater the amount of impurities, the lower the melting point of the substance.
  • Increase boiling point: The greater the amount of impurities, the higher the boiling point of the substance.
 
Effect of pressure on boiling point (Optional)
  • As pressure acting on liquid increases, the boiling point increases.
  • As pressure acting on liquid decreases, the boiling point decreases.
Next: Separation Techniques
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  • Home
  • More Information
  • Contact Me
  • Blog
  • FREE 5-MIN Notes
    • 1. Experimental Techniques
    • 2. Methods of Purification
    • 3. Separation Techniques
    • 4. Qualitative Analysis
    • 5. Kinetic Particle Theory
    • 6. Atomic Structure
    • 7. Elements, Compounds, Mixtures
    • 8. Ionic Bonding
    • 9. Covalent Bonding
    • 10. Mole Concept
    • 11. Electrolysis
    • 12. Energy Changes
    • 13. Speed of Reaction
    • 14. Redox
    • 15. Acids and Bases
    • 16. Salts
    • 17. Ammonia
    • 18. Periodic Table
    • 19. Metals
    • 20. Air
    • 21. Fuels
    • 22. Organic Chemistry
    • 23. Macromolecules
  • Free Printables