Sneaky Light Absorbers
Crush a leaf, add rubbing alcohol, and use a strip of paper to pull apart the hidden colours inside. Run it twice — once with a coffee filter, once with chromatography paper — and see what science-grade equipment actually changes.
7-12 yrs
Medium
30
min
Stage 3
Mission Briefing.
Designed by Darin Carr (BSc, DipEd)
NESA Accredited Teacher Chemistry & Physics Specialist
Creator of the LAB™ Learning System
Essy
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Sneaky Light Absorbers
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NESA Accredited Teacher
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High school chemistry & physics specialist 30+ years
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The Crazy Scientist in primary schools — 15 years
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International conference presenter on science education
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Creator of the LAB™ Learning System
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Curriculum aligned: NSW Science & Technology K–6 (2024)
A picture is worth a thousand words — check this out and see if you can spot the science hiding in plain sight.
Mission Equipment
A handful of fresh dark green spinach leaves
Rubbing alcohol/isopropyl alcohol
2 small glass jars or heatproof cups
A mortar and pestle
Scissors
strips of coffee filter paper
2 strips of chromatography paper (available online on Amazon)
2 pencils or chopsticks
Tape / paperclip
A large heatproof bowl or tray
Hot water - adult supervision required
Pot holders or oven mitts
Let’s Investigate
1
Prepare the leaves
Using scissors, cut your leaves into small pieces — the smaller the better.
Spinach and silverbeet work brilliantly because
3
Divide the leaves
Divide the leaf paste as evenly as possible between your two glass jars.
Pour just enough rubbing alcohol into each jar to completely cover the leaf pieces.
Both jars must have the same amount of leaf and the same amount of alcohol — this is your fair test.
5
Prepare the strips
While the jars are in the hot water bath, prepare your strips. Tape one coffee filter strip to the middle of one pencil, and one chromatography paper strip to the middle of the other.
The strip should hang down far enough to touch the alcohol when the pencil rests across the top of the jar — but the strip must NOT touch the bottom or sides of the jar.
7
Watch & Wait
Leave both strips undisturbed for 20–30 minutes.
Watch the green alcohol travel up the paper.
As it moves, it carries the pigments with it — but each pigment travels at a different speed.
2
Crush the leaves
Use the pestle to grind the leaf pieces into a dark green paste.
You want to break open as many leaf cells as possible — the more you crush, the more pigment you release.
Keep going for at least 2–3 minutes until you have a thick, dark paste.
4
Heat the jars
Fill your large heatproof bowl with very hot water.
Carefully place both jars into the water bath using pot holders — the water should come up the sides of the jars but not tip them over. Leave for 20 minutes.
Watch the alcohol slowly turn green as the pigments dissolve out of the cells.
6
Dip the strips
After 20 minutes, carefully remove both jars from the hot water using pot holders. Rest one pencil across each jar so the bottom of each strip just dips into the green alcohol.
Now — before you walk away — make your prediction: which strip do you think will show more colours?
8
Compare
After 30 minutes, carefully remove both strips and lay them flat on a white surface.
How many colour bands can you count on each one?
Which strip shows sharper, more distinct bands?
Which colours can you identify — and do the two strips show the same ones?
Did it work? Share the science! Tag @the_crazy_scientist on Instagram — we love seeing your experiments!
The Crazy Scientist LAB Learning System™
Every experiment follows The Crazy Scientist Lab Learning System™ — a simple way to help kids think like real scientists.
We
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LINK to what they already know,
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ACTIVATE curiosity through hands-on discovery
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BUILD understanding that actually sticks.
Think about the last time you mixed paints. Blue and yellow make green — you know that. But have you ever wondered whether green itself might be hiding other colours inside it?
Here's your prediction before you touch anything: when you pull the pigments out of a leaf and let them travel up a strip of paper — how many different colours do you think you'll find?
Write it down. One colour? Three? Five? You're about to run the same experiment two ways — and find out which version gives you a clearer answer.
How many colour bands appeared on the coffee filter? How many on the chromatography paper?
The same leaf went into both jars. Why are the results different?
The pigments all started at the bottom of the strip at the same time — why did they end up at different heights?
Different pigments travel different distances because of their size and how strongly they stick to the paper — scientists call this chromatography.
A forensic scientist is trying to identify the ink used in a forged document — how could chromatography help crack the case?
Drug testing in sport uses a similar separation technique — what would scientists be separating, and why does equipment precision matter?
If you ran this with a red autumn leaf instead of a green one — would you predict the same bands, different bands, or some overlap?
Where else in science might separating a mixture into its parts reveal something that was hidden?
"Want the full teacher guide? The Crazy Scientist Lab includes classroom delivery tips, how to manage the WOW moment, differentiation for Stage 2 & 3, — ready to teach tomorrow."
Think Like a Scientist
Scientists don't just do ONE experiment; they change one part of the experiment (independent variable) and then see how it affects another part of the experiment
(dependent variable)
Change ONE variable and test again.
Does the type of leaf change which pigments appear — or how many colour bands you see?
Does the concentration of alcohol change how far the pigments travel up the strip?
🧪 Try it! Change ONE thing and test again. What did you discover?
Dr Puddledrip’s Science Tip
Want to go deeper? Tap a section below to explore. ▼
The Science Behind It
Your leaf looks green. But green is actually a disguise.
Chlorophyll absorbs red and blue light and reflects green back at your eyes — the same absorption principle behind the coloured paddles in [Colour Smashers].
But hiding underneath the chlorophyll are other pigments: carotenoids (yellow and orange) and anthocyanins (red and purple). Chlorophyll is so dominant it drowns them out completely.
The alcohol dissolves those pigments out of the crushed cells.
As it travels up the paper, lighter molecules travel further, heavier ones stay low. The result is bands of colour — one for each pigment — separated by the paper.
This is chromatography.
The coffee filter gives a blurry result because its fibres are uneven. Chromatography paper gives sharp, distinct bands because its fibres are perfectly uniform — the same principle used in forensic labs and pharmaceutical testing.
And those autumn colours? When trees stop producing chlorophyll, the green fades — and the hidden pigments finally show through. They were there all summer. You can see light absorption working from a completely different angle in [What Colour Is Your Shadow].
Curiosity spark: What do you think would happen if you ran this experiment with a leaf that has already turned red or orange in autumn — would you still see the same bands, or completely different ones?
Find out in The Crazy Scientist Lab.
Extension: G&T Years 5 & 6
Vocabulary
Know a parent or teacher who'd love this? Send it on! 👇
READY TO TEACH THIS
TOMORROW?
Running the experiment is easy; however, teaching it well is another challenge.
Teachers often ask:
How do I adapt this for Stages 1,2 or 3?
What do I do with fast finishers?
What misconceptions will they have?
How do I structure this for a full class?
What syllabus outcomes does it cover?
What do I say when they ask WHY?
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