Year 10 - Science
Comparing types of chromatography: including gas chromatography
Separating substances
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This pupil-friendly study guide includes a unit summary, clear notes, common mistakes, and quick questions with answers.
Unit Summary
This unit explores purification techniques, including filtration, crystallisation, and distillation. It explains formulations, uses chromatographic methods to identify pure and impure substances, and interprets chromatograms with Rf values. The emphasis is on accurate measurements.
Lesson Summary
You will learn to identify features of different types of chromatography and describe how the techniques are used to separate and identify components of a mixture.
Key Notes
- Paper, thin layer (TLC), and gas chromatography (GC) can all distinguish between pure and impure substances.
- Chromatographic processes use a mobile and stationary phase. TLC and GC both use silica/alumina as a stationary phase.
- Thin layer chromatography (TLC) uses locating agents to develop chromatograms and aid analysis of them.
- Chromatograms from gas chromatography (GC) also provide details about the amount of each component in a sample.
- Retention factors (Rf) and retention times both provide quantitative information about a sample's components.
Vocabulary To Learn
- stationary phase: A surface along which the solvent (and any dissolved components) travels. It does not move during chromatography.
- mobile phase: The movement of a solvent and any dissolved components of a sample along the stationary phase in chromatography.
- chromatogram: The resultant pattern of a sample's components on the stationary phase after chromatography has been carried out.
- thin layer chromatography: A type of chromatography that uses a thin layer of an inert substance spread over an unreactive flat surface as the stationary phase and a liquid state substance for the mobile phase.
- gas chromatography: A type of chromatography that uses an inert substance packed into a coiled tube as the stationary phase and an unreactive/inert gas as the mobile phase.
Common Mistakes To Avoid
- Pupils sometimes struggle to understand how using different mobile and/or stationary phases affects the resulting chromatograms.
3 Quick Questions (With Answers)
1. Explain the scientific idea in this lesson using two key points.
Paper, thin layer (TLC), and gas chromatography (GC) can all distinguish between pure and impure substances. Chromatographic processes use a mobile and stationary phase. TLC and GC both use silica/alumina as a stationary phase.
2. Define this scientific word and use it in context. 'stationary phase'
A surface along which the solvent (and any dissolved components) travels. It does not move during chromatography. Include the word in a full scientific explanation, not as a single label.
3. Correct this common scientific misunderstanding.
Mistake: Pupils sometimes struggle to understand how using different mobile and/or stationary phases affects the resulting chromatograms. Correction: Perform chromatography of the same mixture using different mobile phases/stationary phases and discuss the pros/cons of each combination.
More Lessons In This Unit
- Chromatography: paper Study Guide
- Chromatography: separating a mixture of inks Study Guide
- Crystallisation Study Guide
- Distillation: fractional distillation Study Guide
- Distillation: separating a mixture of inks Study Guide
- Distillation: simple distillation Study Guide
- Filtration Study Guide
- Interpreting chromatograms Study Guide
- Potable water Study Guide
- Potable water: including sedimentation Study Guide
- Separating mixtures Study Guide
- Separating mixtures (including formulations) Study Guide
- Solutions Study Guide
- Wastewater treatment Study Guide
- Water sample analysis: dissolved solids Study Guide
- Water sample analysis: distillation Study Guide
- Water sample analysis: pH Study Guide
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