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SavannahYear 8
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ScienceMixtures and solutions25 min★★ difficulty

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
  • 16 parts to scroll through
  • 4 quick checks
  • Marked quiz at the end
  • Gentle pace: short sittings with pauses

Words to know

conceptsubstancemixturesseparatedfiltration

Scroll down — the lesson carries on below

Part 1 of 16 · Discover6%
1

Watch & discover

Part 1 of 16

Watch first

Chromatography: separating what looks identical

An English teaching video on this topic from FuseSchool - Global Education. Watch it, then scroll down for the lesson.

In a nutshell

Understand the concept of a pure substance and how mixtures can be separated through filtration, distillation and chromatography

2

Learning cycle

Part 2 of 16

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.

3

Explore the idea

Part 3 of 16

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.

4

Explore the idea

Part 4 of 16

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.

5

Quick check

Part 5 of 16

Quick check

What does 'pure' mean in science?

6

Quick check

Part 6 of 16

Quick check

Why must the start spot sit above the solvent level?

7

Reset break

Part 7 of 16

Pause

That's sitting 1 of 2 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.

Stop here for now
8

Learning cycle

Part 8 of 16

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.

9

Explore the idea

Part 9 of 16

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.

10

Quick check

Part 10 of 16

Quick check

Which substance travels furthest up the paper?

11

Quick check

Part 11 of 16

Quick check

Which method separates sand from water?

12

Explore the idea

Part 12 of 16

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.

13

Challenge round

Part 13 of 16

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

14

Challenge round

Part 14 of 16

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.

15

Mastery quiz

Part 15 of 16

Marked quiz

End of lesson quiz: Chromatography: separating what looks identical

4 questions, marked with the reasoning shown. No timer.

  1. 1. What does 'pure' mean in science?

  2. 2. Why must the start spot sit above the solvent level?

  3. 3. Which substance travels furthest up the paper?

  4. 4. Which method separates sand from water?

16

Lesson round-up

Part 16 of 16

Lesson round-up

Ready when you are

Quiz score

Not sat

Games

Not played

Points this lesson

0

Best run

0 in a row

Luna: 0 out of 4 on the practice checks. Only if you feel up to it — one more?

Ask Luna

Do the work

Your written work for this lesson

This is the part you'd do in your book at school. Pick the pieces below, write here or on paper, and photograph anything you draw or work out.

Case study

Why the school greenhouse failed

A science club grew tomato plants in the school greenhouse. In June the plants grew well: leaves were dark green and the fruit set quickly. In July the club went away for two weeks and left the greenhouse door shut. When they came back, the leaves were curled and pale and most of the fruit had dropped.

The club had a data logger inside. It showed the temperature reached 46 °C on several afternoons and the soil moisture fell close to zero. The club knew photosynthesis needs light, water and carbon dioxide, and that enzymes in a plant work best in a narrow range of temperature. Above that range the enzymes stop working properly.

The club repeated the summer with the door propped open and a water bottle drip on each pot. Temperature peaked at 31 °C and the plants survived.

Written for Good Learning Co.

Reading questions

  1. Name the variable the club changed the second time, and one variable they kept the same.
  2. Explain, using the words photosynthesis and enzymes, why the plants were damaged in July.
  3. Write a conclusion for the club's report, saying how far the evidence supports it.

  • Method and results

    Writing

    Write the aim, what you changed, what you measured and what you kept the same, then record your results in a table.

    1 page + results table

  • Conclusion

    Writing

    Explain what your results show and why, using the scientific words from the lesson. Say how you know you can trust them.

    6–8 sentences

  • Labelled diagram

    Diagram

    Draw the apparatus or the process in pencil, label it fully, and photograph it.

    1 labelled diagram

  • Reading and notes

    Reading

    Read the lesson text again and write the key ideas in your own words.

    Half a page of notes

Saved as you type.

Part 1 of 16 · Watch & discover

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    Understand the concept of a pure substance and how mixtures can be separated through filtration, distillation and chromatography

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