🎯 Common Question Types:
- Calculate Rf values from distance data (1–2 marks)
- Describe the paper chromatography method (3–4 marks)
- Interpret a chromatogram: identify pure/mixture, match substances (2–3 marks)
- Explain why substances separate (2 marks)
- Evaluate the method — limitations and improvements (2–3 marks)
📝 Key Command Words:
- Describe: State observations — number of spots, positions
- Explain: Give reasons why separation occurs (different affinities for phases)
- Calculate: Use Rf = substance distance ÷ solvent distance, show all working
- Suggest: Use knowledge to propose improvements or reasons
⚠️ Common Mistakes to Avoid:
- Confusing mobile and stationary phases (mobile MOVES)
- Measuring from wrong starting point — always from the START LINE
- Giving Rf values greater than 1 — impossible, recheck measurements
- Adding units to Rf values — there are none (it is a ratio)
- Assuming one spot always means pure — it could be two substances with same Rf
This exam tips covers Exam Tips for Chromatography within Chromatography for GCSE Chemistry. Revise Chromatography in Chemical Analysis for GCSE Chemistry with 23 exam-style questions and 15 flashcards. This topic shows up very often in GCSE exams, so students should be able to explain it clearly, not just recognise the term. It is section 12 of 13 in this topic. Treat this as a marking guide for what examiners are looking for, not just a fact list.
Practice questions for Chromatography
What is the purpose of chromatography?
Explain how a chromatogram can be used to determine whether a substance is pure or a mixture.
Quick recall flashcards
What does Rf stand for and what does it measure?
Rf = Retention factor. It measures how far a substance travels compared to the solvent (distance moved by substance ÷ distance moved by solvent)
What is chromatography?
A separation technique used to separate mixtures into their individual components based on different affinities for mobile and stationary phases