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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
· 2 balloons
· Water (about 1 cup)
· 1 tealight candle
· Lighter or matches (adult use only)
· A tray (to catch any drips)
How to do it
1
Prepare the balloons
Fill one balloon with about one cup of water, then tie it off — it will look like a round water bomb. Blow up the second balloon with air and tie it off to the same size.
Teacher Tip: The water balloon works best when it's fairly full — too little water and it won't absorb enough heat. A balloon about the size of a large orange is ideal.
3
Test the air balloon first
Hold the air-filled balloon about 5 cm above the candle flame and start counting. How long before it pops? Make a prediction first — then try it!
5
Inspect the evidence
Lift the water balloon away from the flame and look at the bottom. What do you see? There's a black soot mark — proof the flame was real — but the balloon survived. Why?
2
Light the candle
Place your tealight on a tray and light it. Let the flame settle for 30 seconds until it's burning steadily. Adult to light the candle — students observe.
4
Now try the timebomb!
Hold the water balloon directly over the flame — even touching it. Keep it there! Keep counting. Watch what happens to the flame underneath.
Did it work? Share the science! Tag @the_crazy_scientist on Instagram — we love seeing your experiments!
Water Balloon Timebomb
Designed by Darin Carr (BSc, DipEd)
NESA Accredited Teacher Chemistry & Physics Specialist
Creator of the LAB™ Learning System
Hold a water balloon directly over a candle flame. It should pop any second now. Any second. But it doesn't. Hold an air balloon over the same flame and it goes in an instant. Same balloon. Same flame. So why does one survive?
9-12 yrs
Easy
10
min
Stage 3
>
Water Balloon Timebomb
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 what happens when a balloon gets too close to a candle flame — it pops. Fast. Every single time, no exceptions.
So here's the challenge: what if you held a water balloon directly over the flame and it just… didn't pop? Make your prediction. How long do you think it could last before it goes off?
• Hold an air-filled balloon near the flame. Start counting. (Stand back — it won't last long!)
• Now fill a balloon with water and hold it directly over the same flame. Keep it there. Keep counting.
👉 Why did the air balloon pop so fast when the water balloon just sat there?
👉 Look at the bottom of the water balloon — what did the flame leave behind?
👉 What do you think stopped the rubber from melting?
• Heat from the candle travels through the rubber and straight into the water — that's called heat transfer
• Water needs an enormous amount of energy to heat up — far more than rubber or air
• The heat keeps moving from the rubber into the water, so the rubber never gets hot enough to melt
👉 Think of it like a sponge — the water inside the balloon soaks up heat energy the same way a sponge soaks up a spill, before the surface beneath ever gets wet
• This is why firefighters use water to fight fires, why you sweat when you're hot, and why oceans keep coastal cities cool
Where else does water's ability to absorb heat keep something — or someone — safe?
"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 warm water instead of cold?
What happens if you use less water — how little can you get away with before it pops?
🧪 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
When the candle flame heats the bottom of the balloon, that heat travels through the rubber and straight into the water inside — that movement of heat is called conduction.
Here's the key: water needs an enormous amount of energy to heat up. Far more than rubber, far more than air. Scientists call this specific heat capacity — water's superpower for soaking up heat.
So the heat from the flame keeps moving from the rubber straight into the water, and the rubber never gets a chance to reach the temperature it needs to melt. The water is always one step ahead, draining the energy away.
Think of it like:
• A thin metal spoon left in hot soup heats up almost instantly — there's barely anything there to absorb the energy
• A full pot of water on the same stove takes ages to boil — it's soaking up enormous amounts of heat
• Your water balloon works exactly like that pot — the water inside keeps draining the heat away from the rubber
The soot mark on the bottom is proof the flame was real. The rubber just never got hot enough to care.
Curiosity spark: What do you think would happen if you used less water? Is there a point where the balloon finally runs out of room to absorb the heat?
🔬 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! 👇
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
Keep the science going with these fun experiments
Let's Go!
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Hands-On Science Workshops
Interactive STEM experiences aligned to the NSW syllabus.
