Chromatography
Lesson notes
Overview
Components of a mixture travel at different speeds through a stationary phase. This topic is rated advanced and is number 51 of 110 in Chemistry. Deeper models, formal results and harder reasoning.
What you are seeing
The panel above shows the steps of a process, laid out in order. Click a step to see what happens next. The animation is drawn live from the model, so everything you see responds to the sliders. Press Space to pause, use Restart to replay from the start, and change the speed to slow down quick events.
In depth
Chromatography separates the components of a mixture because they move at different speeds between a stationary phase, such as paper, and a moving solvent. Substances that dissolve well in the solvent and stick less to the paper travel farther. The Rf value, the distance moved by the substance divided by the distance moved by the solvent front, is characteristic for each compound under set conditions. It is used to analyse inks, dyes, drugs and pollutants.
Reading the relationship
The expression "Rf = distance moved / solvent front" is a compact summary of the idea. It uses the symbols R, f, d, i, s, t; name what each one stands for before you start. Notice that it contains a ratio, so increasing the denominator makes the result smaller, and a trigonometric function, so the result repeats as the angle goes round. Then use the sliders to see how changing one quantity changes the others.
A guided exploration
1. Run the animation once with the default settings and describe in words what happens. 2. Change one slider at a time and note which quantity responds most. 3. Push each slider to its extreme and decide whether the result still makes sense.
Try this
Try to explain why the pattern holds, not just what it is. Look for limiting cases and what happens at the edges.
Common pitfalls
Keep the particle picture in mind. Mistakes often come from treating a rate, an amount and an equilibrium position as the same thing, or from ignoring units and conditions.
How it connects
It builds on “Distillation”, the topic before it in Chemistry. Once you are comfortable, continue with “Polymerisation”.
Why it matters
Chemistry links the tiny scale of atoms to the materials, medicines and energy we use every day.
Where you might use it
- Revising “Chromatography” before a class, exam or certification
- Predicting how fast a reaction runs in a lab or an industrial plant
- Choosing materials, medicines and fuels based on how their atoms bond and react
- Reading the labels and data sheets of cleaning products, batteries and food
Frequently asked questions
What is Chromatography?
Components of a mixture travel at different speeds through a stationary phase. It is an advanced topic in Chemistry.
How do I use the Chromatography simulation?
The panel at the top shows the steps of a process, laid out in order. Click a step to see what happens next. Move the sliders one at a time, then press Space to pause the animation and look closer.
What does the formula mean?
The expression Rf = distance moved / solvent front packs the idea into symbols. Name each symbol first, then change one quantity with the sliders and see which others respond.
Who is this topic for?
Deeper models, formal results and harder reasoning. If the quiz feels hard, reread the lesson notes and try the previous topic first.
What should I learn before this?
Start with “Distillation”, the previous topic in Chemistry. Each topic in a subject builds on the ones before it.
How do I track my progress?
Press “Mark as learned” on this page. Progress is stored only in this browser and is never sent anywhere. The Browse page can show topics you have learned or still need to learn.