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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.
From the LAB
What you will need
Three clear cups or glasses
Water
Food colouring — one colour only
2 sheets of paper towel
A flat surface where the setup can sit undisturbed for several hours
How to do it
1
Cup set up
Place two clear cups side to side on a flat surface with a small gap between each, just wide enough for a folded paper towel to arch between them comfortably.
Fill one cup with water and add several drops of food colouring to it, stirring to mix.
3
Predict
Before placing either paper towel bridge: look at your two cups
Write down exactly what you predict will happen once the bridges are in place.
5
Observe & record
Check the experiment at 15 minutes, 30 minutes, and 1 hour.
Each time, record the water level in all cups and note how far the colour has travelled through the paper towel.
If possible, mark the water level on each cup with a marker at each check.
2
Create paper arch
Fold a sheet of paper towel lengthwise several times to make a long, narrow strip — about 2–3 cm wide
The strip needs to be long enough to dip into one cup, arch over the gap, and dip into the next cup.
4
Let's begin
Place one end of the paper towel strip into the full outer cup, arch it over the gap, and place the other end into the empty cup.
6
The turning point
Once the levels have equalised, look closely at the paper towel bridges.
The colour shows exactly how far the water climbed and where it began to descend. Find the apex — the highest point of the arch.
That is where adhesion and cohesion stopped beating gravity and gravity took back over.
Did it work? Share the science! Tag @the_crazy_scientist on Instagram — we love seeing your experiments!
The Colour Climb
Designed by Darin Carr (BSc, DipEd)
NESA Accredited Teacher Chemistry & Physics Specialist
Creator of the LAB™ Learning System
Every tree on Earth is doing something right now that seems impossible: pulling water upward from its roots, against gravity, all the way to its highest leaves. No pump. No motor. No electricity.
5-12 yrs
Easy
20
min
Stage 1-3
>
The Colour Climb
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.
You already know water flows downhill. Pour it from a jug and gravity does the work — it falls. Every river, every waterfall, every raindrop works the same way. Gravity pulls water down.
But here's something to think about before you touch anything: how does a tree move water from the ground to its own leaves? A tall eucalyptus can be 60 or 70 metres high.
There's no pump inside the trunk. No electricity. No motor. Yet water moves from the roots all the way to the highest leaves — upward, against gravity — every single day.
Write down your prediction: if you set up a paper towel bridge between a full cup of coloured water and an empty cup, what do you think will happen — and why? Then set it up and wait.
The water is climbing uphill. What force do you think is pulling it upward — and what is it pulling against?
Look at the paper towel arch carefully. At what point does the water stop going up and start going down? What changes at that exact spot?
When the experiment is finished and the levels have equalised, look closely at the paper towel itself. What do you notice about where the colour has and hasn't reached?
Water just climbed uphill through a paper towel using nothing but the attraction between molecules. Now think about where that same invisible force is quietly doing the same job — at every scale from a bandage to a forest.
A coast redwood can be over 100 metres tall, and it pulls water from the soil all the way to its highest leaves every day. What do you think is inside the tree's trunk that acts like the paper towel fibres — and how narrow do those passages need to be for capillary action to work against that height of gravity?
When you put a bandage on a cut, the blood wicks into the dressing automatically — you don't have to squeeze it in. What property of the bandage fibres makes that happen, and why does it matter that the fibres are tightly packed?
"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 material make a difference — does water climb faster, higher, or further through paper towel than through a strip of fabric, cotton wool, or tissue paper?
Does the temperature of the water change the speed of the climb — does warm water travel through the paper towel faster than cold water, and what might that tell you about how the molecules are moving?
🧪 Try it! Change ONE thing and test again. What did you discover?
Want to go deeper? Tap a section below to explore. ▼
The Science Behind It
Water is a polar molecule. Each water molecule has a slightly positive end and a slightly negative end — like a tiny magnet. Paper towel fibres are made of cellulose, which is also polar. Opposite electrical charges attract each other: the water molecules are pulled toward the cellulose fibres. This attraction between unlike molecules is called adhesion.
Once the first water molecules move up into the fibres, they don't go alone. Water molecules are also attracted to each other — a force called cohesion. They pull each other along in a chain, the way a string of paper clips moves when you lift the first one.
Together, adhesion and cohesion create capillary action — a climbing force strong enough to beat gravity over short distances.
But gravity doesn't disappear. As the water climbs higher, gravity pulls back harder. The apex of the paper towel arch is the turning point — the highest point the capillary force can reach before gravity wins. From there, gravity assists, and the water drips down into the empty cup.
The experiment reaches equilibrium when all three cups are at the same water level. At that point, gravity and the capillary force are exactly balanced, and flow stops.
This is not a party trick. It is the mechanism that keeps every forest on Earth alive. The xylem vessels inside a tree trunk are extraordinarily narrow tubes — far narrower than your paper towel fibres. Water molecules are pulled upward through adhesion to the vessel walls and cohesion to each other, in an unbroken chain from the soil all the way to the topmost leaves. In the world's tallest coast redwoods — over 115 metres high — that chain is working against over 11 atmospheres of gravity.
It works because the tubes are narrow enough, and the molecular forces are strong enough.
Curiosity spark: Capillary action works because the passages are narrow. What do you predict would happen if you used a wider material — like a sponge with large pores instead of paper towel with tiny fibres? Would the water climb higher, lower, or not at all?
Extension: G&T Years 5 & 6
Vocabulary
Know a parent or teacher who'd love this? Send it on! 👇
The Crazy Scientist books
These highly visual books combine storytelling and real science, helping students revisit key concepts and stay engaged long after the session.
Designed by a practising NSW classroom teacher (30+ years experience), these books directly support NSW Science & Technology (2024) outcomes and reinforce “Working Scientifically” skills.
Perfect for classroom libraries or home explorations.
For teachers (YouTube)
— Science Before the Bell
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Quick, curriculum-linked science you can teach tomorro
Try Another Crazy Experiment
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Let's Go!
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Hands-On Science Workshops
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