Mixtures and Separation

50 lessons, pages 171–220.

  1. What Is a Mixture? — Two or more substances mingled but not chemically joined
  2. Pure Substances in Chemistry — A single substance with nothing else mixed in
  3. Everyday Pure Versus Chemically Pure — Why pure orange juice is not pure to a chemist
  4. Elements, Compounds and Mixtures — Sorting matter into three families
  5. Mixtures in the Particle Model — Picturing different particles side by side
  6. Mixtures and Compounds: Key Differences — Fixed ratios, new properties and ease of separation
  7. Testing Purity with Melting Points — Sharp melting points and melting ranges
  8. Testing Purity with Boiling Points — How impurities shift the boiling point
  9. Heating Curves of Pure Substances and Mixtures — Flat plateaus versus sloping changes of state
  10. Homogeneous and Heterogeneous Mixtures — Uniform throughout or visibly patchy
  11. Solutions: Solute, Solvent and Solution — The vocabulary of dissolving
  12. Dissolving in the Particle Model — Solute particles spreading between solvent particles
  13. Soluble and Insoluble Substances — What dissolves and what does not
  14. Solubility and Temperature — Reading solubility curves
  15. Saturated Solutions — When no more solute will dissolve
  16. Suspensions and Colloids — Mixtures between solutions and separate layers
  17. Alloys: Solid Mixtures — Brass, bronze and steel as mixtures of metals
  18. Air as a Mixture of Gases — Nitrogen, oxygen, argon and carbon dioxide
  19. Formulations: Mixtures Designed for a Purpose — Paints, medicines and fertilisers in fixed recipes
  20. Choosing a Separation Method — Matching the method to a difference in properties
  21. Sieving and Hand Separation — Separating by particle size
  22. Magnetic Separation — Pulling iron and steel out of a mixture
  23. Decanting — Pouring a liquid off a settled solid
  24. Sedimentation — Letting gravity settle heavy particles
  25. Filtration: How It Works — Separating an insoluble solid from a liquid
  26. Residue and Filtrate — What stays on the filter paper and what passes through
  27. Filtration in Water Treatment — Sand and gravel beds cleaning drinking water
  28. Centrifugation — Spinning mixtures to speed up settling
  29. Evaporation to Recover a Dissolved Solid — Driving off the solvent to leave the solute
  30. Crystallisation — Growing pure crystals from a saturated solution
  31. Obtaining Pure Salt from Rock Salt — Combining dissolving, filtration and crystallisation
  32. Separating Immiscible Liquids — Layers and the separating funnel
  33. Simple Distillation — Boiling off a solvent and condensing it back
  34. Inside the Condenser — How cooling water turns vapour back into liquid
  35. Distillation Apparatus and Safe Practice — Thermometer position, even boiling and hazards
  36. Desalination: Drinking Water from Seawater — Distillation on a large scale and its energy cost
  37. Miscible Liquids and Boiling Points — Why mixed liquids need a better method
  38. Fractional Distillation — Separating liquids with close boiling points
  39. The Fractionating Column — A temperature gradient and repeated condensation
  40. Fractional Distillation of Crude Oil — Fractions, boiling ranges and their uses
  41. Separating Gases from Liquid Air — Obtaining nitrogen, oxygen and argon
  42. What Is Chromatography? — Separating dissolved substances as they travel
  43. Paper Chromatography — Spots, a baseline and a rising solvent
  44. Mobile and Stationary Phases — Why substances travel different distances
  45. Reading a Chromatogram — Counting spots and comparing positions
  46. Calculating Rf Values — Distance moved by spot ÷ distance moved by solvent
  47. Identifying Substances with Chromatography — Matching unknown spots to known references
  48. Chromatography and Purity — One spot or many and uses in forensics and food testing
  49. Planning a Multi-Step Separation — Designing a sequence to separate a complex mixture
  50. Mixtures and Separation: Unit Review — Connecting purity, mixtures and every separation method