AQA · GCSE · Chemistry
Course version: 8462 · Version from Sept 2018
Students should be able to: describe, explain and give examples of the…
Full specification wording
Mixtures: Students should be able to: describe, explain and give examples of the specified processes of separation suggest suitable separation and purification techniques for mixtures when given appropriate information.
You need to describe how each separation process works, explain why it separates the components, and give examples.
Checked against the AQA 8462 specification (opens in a new tab) on .
- Point 5 of 5
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
You need to describe how each separation process works, explain why it separates the components, and give examples. Filtration separates an insoluble solid from a liquid, for example sand from salt solution. Crystallisation recovers a dissolved solid, for example copper sulfate crystals from solution. Simple distillation separates a solvent from a solution, for example pure water from sea water. Fractional distillation separates miscible liquids with different boiling points, for example ethanol from water. Chromatography separates dissolved substances, for example dyes in ink. When given information about a mixture, choose the technique that matches the components and their properties.
What earns the marks
- Describe filtration as separating an insoluble solid from a liquid using filter paper and a funnel, and explain that the solid particles are too large to pass through the paper.
- Describe crystallisation as evaporating some solvent to form a saturated solution, then cooling or leaving it so crystals of the dissolved solid form.
- Describe simple distillation as heating a solution to evaporate the solvent, then condensing the vapour to collect the pure solvent.
- Describe fractional distillation as separating miscible liquids with different boiling points using a fractionating column, with the lower-boiling liquid distilling first.
- Describe chromatography as separating dissolved substances using a stationary phase and a mobile solvent, where components travel different distances.
- Suggest a suitable technique by matching the mixture information to the property difference, such as solubility, boiling point or particle size.
Common mistakes and how to put them right
Choosing filtration for a dissolved solid.
Put it right: Use crystallisation or evaporation because the solid is not insoluble.
Using simple distillation for two miscible liquids with similar boiling points.
Put it right: Use fractional distillation for better separation.
Describing chromatography without mentioning the stationary phase and mobile phase.
Put it right: State that the solvent moves through the stationary phase and carries components different distances.
Exam tips
- Read the mixture information carefully and name the property difference before choosing a technique.
- Give a named example for each process, such as sand and salt solution for filtration or ink dyes for chromatography.
- Link each step of your method to why it separates the components, rather than listing apparatus only.
Try the lesson
The start of the Mixtures: Students should be able to: describe, explain and give examples of the specified processes of separation suggest suitable separation and purification techniques for mixtures when given appropriate information. lesson, made from checked teaching notes for this specification point.
Have a go first
Which separation technique is used to separate the colours in a sample of ink?
Listen
You need to describe how each separation process works, explain why it separates the components, and give examples. Filtration separates an insoluble solid from a liquid, for example sand from salt solution. Crystallisation recovers a dissolved solid, for example copper sulfate crystals from solution. Simple distillation separates a solvent from a solution, for example pure water from sea water. Fractional distillation separates miscible liquids with different boiling points, for example ethanol from water. Chromatography separates dissolved substances, for example dyes in ink. When given information about a mixture, choose the technique that matches the components and their properties. A strong answer earns marks for these points. Describe filtration as separating an insoluble solid from a liquid using filter paper and a funnel, and explain that the solid particles are too large to pass through the paper. Describe crystallisation as evaporating some solvent to form a saturated solution, then cooling or leaving it so crystals of the dissolved solid form. Describe simple distillation as heating a solution to evaporate the solvent, then condensing the vapour to collect the pure solvent. Describe fractional distillation as separating miscible liquids with different boiling points using a fractionating column, with the lower-boiling liquid distilling first. A common slip: Choosing filtration for a dissolved solid. Instead, use crystallisation or evaporation because the solid is not insoluble. Exam tip: Read the mixture information carefully and name the property difference before choosing a technique.
Key words
Say what each word means before you turn the card.
Filtration
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Crystallisation
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Simple distillation
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Chromatography
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See every definition
- Filtration
- Separates an insoluble solid from a liquid using filter paper and a funnel, because the solid particles are too large to pass through the paper.
- Crystallisation
- Evaporating some solvent to form a saturated solution, then cooling or leaving it so crystals of the dissolved solid form.
- Simple distillation
- Heating a solution to evaporate the solvent, then condensing the vapour to collect the pure solvent.
- Chromatography
- Separating dissolved substances using a stationary phase and a mobile solvent, where components travel different distances.
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