Study Notes
Separation techniques are used to separate mixtures into their individual components and assess their purity. These methods include filtration, crystallisation, distillation, fractional distillation, and paper chromatography.
- Pure Substance — a single element or compound not mixed with any other substance Example: Pure milk
- Filtration — separates an insoluble solid from a liquid Example: Chalk and water
- Crystallisation — separates a soluble solid from a solution Example: Copper sulfate crystals from solution
- Distillation — separates liquids based on different boiling points Example: Salt water to fresh water
- Fractional Distillation — separates mixtures into fractions using a fractionating column Example: Crude oil into petrol and LP gas
- Paper Chromatography — separates substances based on their movement through paper Example: Separating chlorophyll pigments
Exam Tips
Key Definitions to Remember
- Pure Substance: A single element or compound not mixed with others
- Filtration: Separation of an insoluble solid from a liquid
- Crystallisation: Formation of solid crystals from a solution
- Distillation: Separation of liquids based on boiling points
- Fractional Distillation: Separation of a mixture into fractions using a column
- Paper Chromatography: Separation of substances based on movement through paper
Common Confusions
- Confusing distillation with filtration
- Misunderstanding the purpose of a fractionating column
Typical Exam Questions
- What is the purpose of filtration? To separate an insoluble solid from a liquid
- How does crystallisation work? By evaporating the solvent to leave solid crystals
- What is the difference between distillation and fractional distillation? Fractional distillation uses a fractionating column for more complex mixtures
What Examiners Usually Test
- Understanding of different separation techniques
- Ability to suggest suitable methods for given mixtures
- Knowledge of how purity affects melting and boiling points