Chromatography: separating what looks identical
Two black inks can look the same on paper and be completely different mixtures. Chromatography spreads a mixture out so you can count what is really in it.
Part of your national curriculum
- Chemistry: pure and impure substances: Understand the concept of a pure substance and how mixtures can be separated through filtration, distillation and chromatography
Lesson overview
What you'll learn in this lesson
Understand the concept of a pure substance and how mixtures can be separated through filtration, distillation and chromatography
Key learning points
- • Pure substance or mixture?
- • How chromatography works
- • Choosing the right separation
This lesson at a glance
- 25 minutes
- 20 parts to scroll through
- 4 quick checks
- Marked quiz at the end
- Gentle pace: short sittings with pauses
Words to know
Scroll down — the lesson carries on below
Watch & discover
Part 1 of 20
Visual introductionPicture this
Chromatography: separating what looks identical
Two black inks can look the same on paper and be completely different mixtures. Chromatography spreads a mixture out so you can count what is really in it.
In a nutshell
Understand the concept of a pure substance and how mixtures can be separated through filtration, distillation and chromatography
Learning cycle
Part 2 of 20
Learning cycle 1 of 2
Part 1 · Pure substance or mixture?
A short piece of teaching, then a check to make sure it has landed.
Explore the idea
Part 3 of 20
Learn
Pure substance or mixture?
In science, pure means a single substance, not merely natural or clean. A pure substance melts and boils at fixed temperatures; a mixture melts and boils over a range, because its components have different properties.
Reset break
Part 4 of 20
Pause
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Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.
Explore the idea
Part 5 of 20
Learn
How chromatography works
A spot of the mixture is placed on paper above the solvent level. Solvent travels up the paper, carrying the dissolved substances with it. Substances that are more soluble and less attracted to the paper travel further, so the spot separates into a line of coloured marks.
Quick check
Part 6 of 20
Quick check
Part 7 of 20
Reset break
Part 8 of 20
Pause
That's sitting 2 of 5 done
Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.
Learning cycle
Part 9 of 20
Learning cycle 2 of 2
Part 2 · Choosing the right separation
A short piece of teaching, then a check to make sure it has landed.
Explore the idea
Part 10 of 20
Learn
Choosing the right separation
Filtration separates an insoluble solid from a liquid. Distillation separates a dissolved solid from its solvent, or two liquids with different boiling points. Chromatography separates dissolved substances that stay mixed through both of the others.
Quick check
Part 11 of 20
Reset break
Part 12 of 20
Pause
That's sitting 3 of 5 done
Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.
Quick check
Part 13 of 20
Explore the idea
Part 14 of 20
Worked example
Worked example: reading a chromatogram
A forensic sample shows three spots; pen A shows three spots at the same heights and pen B shows two. Conclusion: pen A is consistent with the sample because every component travelled the same distance under identical conditions. Pen B is missing a component, so it can be ruled out.
Challenge round
Part 15 of 20
Game · Sort it
Which of these are true?
Drag each card into the right column. Tap a card first if dragging is fiddly.
True
Not true
Reset break
Part 16 of 20
Pause
That's sitting 4 of 5 done
Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.
Challenge round
Part 17 of 20
Game · Fill the gaps
Finish the sentences
Choose the word that belongs in each gap.
In science, pure means a single ____, not merely natural or clean.
____ separates an insoluble solid from a liquid.
Challenge round
Part 18 of 20
Game · Recall cards
Which method separates an insoluble solid from a liquid?
Card 1 of 4
Mastery quiz
Part 19 of 20
Marked quiz
End of lesson quiz: Chromatography: separating what looks identical
4 questions, marked with the reasoning shown. No timer.
1. Which method separates an insoluble solid from a liquid?
2. How does distillation obtain pure water from salt water?
3. What does a pure substance have that a mixture does not?
4. A pure substance melts
Lesson round-up
Part 20 of 20
Lesson round-up
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Understand the concept of a pure substance and how mixtures can be separated through filtration, distillation and chromatography