Chromatography
Chromatography separates substances in a mixture because they move at different rates through a medium carried by a solvent.
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Chromatography separates substances in a mixture because they move at different rates through a medium carried by a solvent.
- Rf equals distance moved by substance over solvent
- Pure substances give one spot
- Used to identify food colourings
🧠 Quick quiz
Three questions. Score 2 or more to complete the topic.
What is Chromatography?
Within Chemistry, which covers atoms, bonding, reactions, the periodic table, organic chemistry and the chemistry of everyday life, this topic explains Chromatography. Chemistry links what you can see in the lab to the particles and bonds behind it, so each topic here shows that link in a model.
Check that you can explain Chromatography in your own words and give one example from everyday life. If you can do that, you have understood the core idea.
Understanding Chromatography helps you explain why substances behave as they do, from cleaning products and food to medicines.
Chromatography in detail
In paper chromatography, a spot of the mixture is placed on a pencil line on chromatography paper, which is stood in a solvent. As the solvent rises, different substances move different distances depending on how soluble they are and how strongly they stick to the paper.
The Rf value = distance moved by the substance ÷ distance moved by the solvent, and it can be compared with known values to identify compounds. A pure substance gives a single spot. Chromatography is used to analyse inks, food colourings, drugs and pollutants, and in forensic science.
How the interactive helps you understand Chromatography
Click a step, or use the Previous and Next buttons, to move through the sequence one stage at a time. Auto-play moves on for you.
Before you change anything, predict the result. Then change one value at a time and check whether your prediction was right. This is a quick way to build a correct mental model of Chromatography.
Real-life uses and examples
- Use Chromatography to explain what happens in a lab experiment and why.
- Link Chromatography to everyday products such as cleaning agents, food and medicines.
- Read a chemical equation or diagram and work out what Chromatography shows.
Common mistakes to avoid
- Describing what happens without explaining the particles or bonds involved.
- Mixing up the names of substances or ions when you describe Chromatography.
- Learning the definition without testing it. Use the quiz and the interactive to check that you can apply the idea.
Frequently asked questions about Chromatography
What is Chromatography?
Chromatography separates substances in a mixture because they move at different rates through a medium carried by a solvent.
What are the most important points about Chromatography?
The main points are: Rf equals distance moved by substance over solvent; Pure substances give one spot; Used to identify food colourings.
Why is Chromatography useful?
Understanding Chromatography helps you explain why substances behave as they do, from cleaning products and food to medicines.
How can I practise Chromatography?
Open the interactive at the top of this page and change the controls one at a time. Predict the result before each change, then take the three-question quiz. A score of two or more marks the topic as complete on this device.
Which topics are related to Chromatography?
Related topics in Chemistry include Hard and Soft Water, The Greenhouse Effect, Tests for Gases.