Summary
Methods of separating and purifying substances involve various techniques to isolate and purify components in mixtures based on their physical properties. These methods are essential in both laboratory and industrial settings to obtain pure substances for further use.
- Distillation — a process to separate a pure liquid from a mixture based on different boiling points.
Example: Separating ethanol from water. - Fractional Distillation — similar to distillation but uses a fractionating column to separate components with closer boiling points.
Example: Obtaining petrol from crude oil. - Filtration — a method to separate an insoluble solid from a liquid.
Example: Separating chalk from water. - Crystallisation — a technique to form solid crystals from a solution.
Example: Obtaining copper sulfate crystals from its solution. - Paper Chromatography — used to separate and identify components in a mixture based on their movement through a paper in a solvent.
Example: Separating pigments in chlorophyll.
Exam Tips
Key Definitions to Remember
- Distillation: Separating liquids based on boiling points.
- Filtration: Separating solids from liquids using a filter.
- Crystallisation: Forming solid crystals from a solution.
- Chromatography: Separating substances based on their movement through a medium.
Common Confusions
- Confusing distillation with filtration, which separates based on solubility, not boiling points.
- Misunderstanding that chromatography requires a suitable solvent for separation.
Typical Exam Questions
- What is a precipitate (ppt)?
An insoluble solid that emerges from a liquid solution. - Here is a solution containing ethanol and water. How would you separate one from another?
Fractional distillation - To separate a mixture of salt and water what separation method is used?
Evaporation
What Examiners Usually Test
- Understanding of different separation techniques and their applications.
- Ability to identify the correct method for separating specific mixtures.