The Impossible Water Drop Trick

NESA Accredited Teacher Chemistry & Physics Specialist

Creator of the LAB™ Learning System

Explore how many drops of water can be placed on a coin before it bursts!

5-12 yrs

Easy

5 min

Stage 2

Experiments >

Forces, Motion & Balance

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The Impossible Water Drop Trick

NESA Accredited Teacher
High school chemistry & physics specialist 30+ years
The Crazy Scientist in primary schools — 15 years

International conference presenter on science education
Creator of the LAB™ Learning System
Curriculum aligned: NSW Science & Technology K–6 (2024)

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A picture is worth a thousand words — check this out and see if you can spot the science hiding in plain sight.

What you will need

1 x 5 cent coin
Water
Dropper (or straw / spoon)

How to do it

1

Set up your coin

Place a 5 cent coin on a flat surface.

3

Add water drops carefully

2

Get your water ready

Fill a dropper with water.

4

Watch the dome form

If it stays, look at how it acts as a magnifying lens on the coin!

Did it work? Share the science! Tag @the_crazy_scientist on Instagram — we love seeing your experiments!

The Crazy Scientist Lab System™

Every experiment follows The Crazy Scientist Lab System™ — a simple way to help kids think like real scientists.

LINK to what they already know,
ACTIVATE curiosity through hands-on discovery
BUILD understanding that actually sticks.

Have you ever seen water pile up like a tiny bubble without spilling? It looks like it should fall straight off… but it doesn’t!

As you carefully add drops of water, something strange starts to happen.
Instead of spreading out, the water sticks together and forms a curved dome.

This molecular attraction — called cohesion — is what lets water striders walk on the surface of a pond without sinking, what pulls water up through the stems of plants against gravity (sometimes metres high), and what makes rain form round droplets instead of spreading into a flat mist.
Without surface tension, plants couldn't drink, insects couldn't skate across water, and rain would feel completely different.

Where else in nature do you think this invisible "skin" on water is working?

"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.

What happens if you use a different coin?

What happens if you change the liquid?

🧪 Try it! Change ONE thing and test again. What did you discover?

The Science Behind It

Water molecules stick to each other due to cohesion.

This creates surface tension, which:

Pulls the water into a dome shape
Allows more water to sit on top than expected

The curved surface acts like a stretched skin:

Holding the water together
Preventing it from spilling immediately

Surface tension is what allows the water to “pile up.”

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.

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