Step 1 of 5 · Predict
Before you test: what's your guess?
Dip the corner of a paper towel in water and the water creeps upward — against gravity — with nothing pushing it. Something in the towel itself is doing the pulling.
“Same rule as last time — guess first, test second. Being wrong on purpose is the fast way to learn.”
What other kids guessed
Step 2 of 5 · Experiment
Test it in your kitchen.
Fourteen minutes, mostly waiting and watching. Tap each step as you finish it.
“Check on it every couple of minutes rather than staring the whole time — the climb is slow enough to miss if you blink.”
You'll need
- A glass of water
- A strip of paper towel
- Food colouring (any colour)
- A clock or timer
Step 3 of 5 · Explain
Here's what's actually happening.
Water molecules are stubbornly attracted to each other and to the paper's fibers. That double attraction is called capillary action — as fibers pull a few molecules up, those molecules pull their neighbours along behind them.
Paper towel
Many tiny gaps
Narrow gaps between threads give water lots of paths to climb at once.
Plastic wrap
None gaps
A smooth surface with nothing to grip, so the water stays put.
The same effect carries water from a tree's roots all the way up to its highest leaves.
Step 4 of 5 · Check yourself
Predict the next one.
You dip a strip of paper towel and a strip of plastic wrap side by side into the same coloured water. What happens to the plastic wrap?
“Think about what capillary action actually needs — a material full of tiny gaps for water to grip.”
Step 5 of 5 · Record it
Write it down properly.
Print the lab sheet and log how high the water climbed every two minutes for both strips — you'll compare climb rates across materials in a later lesson.
“Print the lab sheet before you forget the timings. Future you will thank present you.”
Lesson complete!
That's every step of “Why does water climb up a paper towel?” finished. Fern the Fox is impressed.