Who this is for: Cambridge IGCSE Coordinated Science (0654) students who want methods of purification — choosing and describing separation techniques — to become a reliable source of marks instead of a diagram-labelling exercise.
What query it owns: how to understand and revise methods of purification in Cambridge IGCSE Coordinated Science.
Why this is safe: this page owns the methods-of-purification revision-guide angle, while Tutopiya’s Methods Of Purification subtopic page owns the learning resource and the free Methods Of Purification quiz owns the practice.

Separating and purifying substances is a core practical skill in Coordinated Science. Cambridge IGCSE (0654) expects you to match each technique to the type of mixture — solid from liquid, liquid from liquid, dissolved solid from solution — and describe the method clearly. This guide links each purification method to when examiners expect you to use it.

Key takeaways

• Filtration separates an insoluble solid from a liquid.
• Crystallisation obtains a pure solid from a solution by evaporating solvent slowly.
• Simple distillation separates a solvent from a dissolved solid (e.g. salt water → water).
• Fractional distillation separates liquids with different boiling points (e.g. ethanol and water).
• Paper chromatography separates dissolved substances based on different solubilities in the solvent.

What are methods of purification in Cambridge IGCSE Coordinated Science?

Methods of purification separate the components of a mixture or remove impurities from a substance. The method depends on the physical properties involved — particle size (filtration), solubility (crystallisation, chromatography), or boiling point (distillation). Choosing the correct technique for a given mixture is one of the most commonly tested practical skills.

You can read the full explanation, labelled diagrams and notes on Tutopiya’s Methods Of Purification subtopic page before you attempt questions.

Choosing the right purification method

Method	Mixture type	Property used	Example
Filtration	Insoluble solid + liquid	Particle size	Sand from water
Crystallisation	Solid dissolved in liquid	Solubility decreases on cooling	Pure copper sulfate crystals
Simple distillation	Solvent + dissolved solid	Boiling point of solvent	Pure water from salt water
Fractional distillation	Two or more liquids	Different boiling points	Ethanol from fermented mixture
Chromatography	Dissolved substances	Different solubilities in solvent	Separating ink dyes

Simple vs fractional distillation

Feature	Simple distillation	Fractional distillation
Mixture separated	Solvent from dissolved solid	Two or more liquids
Apparatus	Distillation flask, condenser	Fractionating column + condenser
Example	Obtaining pure water	Separating crude oil fractions
Key idea	Collect vapour of lower-boiling component	Repeated evaporation and condensation in column

Methods of purification in past-paper wording: command words that matter

Command word / phrase	What the question wants	Typical purification stem
Name the method	Identify technique	”Name the method used to obtain pure water from seawater.”
Describe	Outline steps	”Describe how to obtain pure copper sulfate crystals.”
Explain why	Justify choice	”Explain why fractional distillation is used instead of simple distillation.”
Draw / label	Show apparatus	Label a distillation or filtration diagram

Worked exam-style stems (how to answer the wording)

1. “Name the method used to separate insoluble sand from water.” Filtration. Mark-scheme reward: filtration (or filter).
2. “Describe how to obtain pure copper sulfate crystals from a solution.” Heat the solution to evaporate some water, then leave to cool so crystals form; filter and dry the crystals. Reward: evaporation/cooling and crystal formation.
3. “Explain why fractional distillation is needed to separate ethanol and water.” Their boiling points are close together (78 °C and 100 °C); the fractionating column gives better separation through repeated condensation and evaporation. Reward: close boiling points and role of fractionating column.

Test yourself with the Methods Of Purification quiz once you can match methods to mixture types.

How methods of purification connect to the rest of Coordinated Science

Purification links to Criteria Of Purity — you test the product’s melting point after purification — and to Elements, Compounds And Mixtures. The Cambridge IGCSE Coordinated Science resource hub links every Experimental Techniques subtopic.

Common mistakes students make

• Using filtration to separate two dissolved liquids (use distillation).
• Using simple distillation when fractional distillation is needed for two liquids.
• Confusing crystallisation (solid from solution) with evaporation to dryness (may decompose the solid).
• Forgetting the condenser in distillation — vapour must be cooled back to liquid.
• Saying chromatography separates insoluble solids (it separates dissolved substances).

When you need more support

If purification method questions keep costing marks, work through the Methods Of Purification quiz, then get focused help from a Cambridge IGCSE Coordinated Science tutor.

Frequently asked questions

Is methods of purification hard in Coordinated Science? The techniques are limited in number — marks are lost when students pick the wrong method for the mixture type.

What is the difference between simple and fractional distillation? Simple distillation separates a solvent from a dissolved solid; fractional distillation separates liquids with different boiling points using a fractionating column.

When do you use crystallisation? To obtain a pure solid from a solution, by evaporating some solvent and cooling so the solid crystallises out.

How do I revise methods of purification effectively? Learn which method suits each mixture type, sketch apparatus diagrams, then take the Methods Of Purification quiz.

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