- Age:6+
- Time:45 min
- Difficulty:Medium
- Mess level:Medium
- Supervision:Yes
🧒 In one sentence
A few simple balloon tricks reveal big science: gas that blows them up, water that fireproofs them, and spread-out pressure that lets them rest on a bed of pins.
👨👧 Adult supervision needed
These five experiments include an open candle flame (experiment 2), sharp pins (experiment 3), and a skewer (experiment 4). An adult should handle the flame and sharp tools, keep water nearby when the candle is lit, and supervise younger children throughout.
One thing to expect in experiment 2: the water balloon will burst eventually, once the flame has heated all the water through. That is the experiment finishing, not a mistake - but it means about 200 ml of water landing on a lit candle, so hold it over a tray, a sink, or the garden rather than the kitchen table, and keep faces well back the whole time.
The brief history of the balloons
First balloons, as archeological findings show, were made from animal intestines, especially from pig bladders. Archeological findings also show that first balloon sculptures were used by Aztecs. They were made from cat intestines and were presented as a sacrifice to the gods.
The first rubber balloon was made in the year 1824 by Professor Michael Faraday. He was using them for experiments he was conducting with the hydrogen. He described the balloons as caoutchouc bags that are highly elastic and that they can expand by forcing the air into them until caoutchouc becomes transparent. He also explains how they, when expanded by hydrogen, become so light that they possess considerable ascending power. Faraday made his first balloons by making two sheets of rubber and connecting the edges of those two sheets to each other. Since the rubber was tacky, he had to put flour in the middle so the rubber does not connect. On edges, the rubber would connect automatically due to its stickiness.
Latex rubber balloons were invented and pioneered in the year 1825 by rubber manufacturer Thomas Hancock. Vulcanized balloons were introduced in the year 1847 by J.G. Ingram and they were the first balloons that were not affected by changes in temperature. Vulcanized balloons are regarded as the prototype of the modern-day balloons.
Modern-day balloons are made from different materials but mostly rubber, latex, polychloroprene, and nylon fabric. Also, we can find today’s balloons in many different shapes, sizes, and colors.
Modern balloons come in countless shapes, sizes and colors.
From rubber, latex, polychloroprene, and nylon fabric, we have balloons in many shapes, sizes, and colors today.
Physics principles of the balloons
We all know that balloons fly. Ok, fall slowly. But did you know there is science behind why is that so? Let’s dive into some physics and explore the principles of why balloons “fly”.
When we inflate the balloon with regular, atmospheric air, the air pressure will become greater than the atmospheric pressure outside of the balloon.
Air pressure actually represents how many particles collide with the surface at any given time. Since there is less space in the balloon, they collide and bounce off the inside surface a lot more than particles from outside do. This happens because of the density. The more particles are in the same space (like in the balloon), the more frequent will they collide with the wall or surface.
To understand why balloons “fly”, it is important to understand how air pressures function. Air pressures outside of the balloon and inside try to even out. The force from the inside of the balloon makes the balloon to expand while the forces from the outside of the balloon make it contract. With this knowledge, we could assume that the balloon with high air pressure would expand until the air pressures are equal inside and outside.
But there is a twist! Balloons possess certain elasticity that plays an important role. Now the air inside needs to have a lot more pressure since it must counteract the elastic membrane of the balloon that tries to return in the original state and the air pressure from the inside. That makes the balloon light and with some gases like helium even lighter than atmospheric air.
An excellent example of this is the helium balloon. It will rise in the air and, as it gets higher, the atmospheric pressure gets smaller and smaller. The inside of the balloon exerts more pressure because of that, and the balloon may pop from the tension. If it doesn’t pop, helium will slowly leak out through the pores of the balloon, eventually making it fall back down.
Check the video for making all of the activities at the start of the article or continue reading instructions below for each activity if you prefer text description.
1. How to use Science to Blow Up a Balloon
Materials needed for the Experiment
- Balloon
- Vinegar (200 ml)
- Baking soda (2 spoons)
- Empty bottle
- Yarn
- Funnel
Experiment Instructions
Baking soda meets vinegar, and the released carbon dioxide inflates the balloon.
We can use science, vinegar and baking soda to blow up the balloon.
- Pour 200 ml of vinegar into the empty bottle.
- Put the balloon on the funnel and pour 2 spoons of baking soda into it. If you put more, the reaction will be stronger but there is danger of liquid shooting out of the bottle
- Now put the balloon on the bottle, lift it up, so soda drops into the vinegar. After a few seconds the balloon will be blown.
- Use yarn to tie down the balloon and you are done!
The science behind the experiment
When we mix vinegar and baking soda we produce an acid-base reaction. The baking soda (base) takes one hydrogen proton from the vinegar (acid). That turns vinegar into a different substance called sodium acetate and baking soda into the carbonic acid. Carbonic acid is unstable and quickly separates into carbon dioxide gas and water. The gas rises up and since it needs more space it expands into the balloon.
2. Burning a Balloon without popping it
What happens if you hold a water-filled balloon over a candle flame?
Make your prediction, then tap an answer to check!
Materials needed for Burning the Balloon
- Balloon
- Yarn
- Candle
- Matches
- Water
Instructions for Burning the Balloon Experiment
Water inside the balloon absorbs the heat, so the flame does not pop it.
With water, we can even make a fragile balloon resistant to fire.
- Put the balloon onto the faucet and let it fill with water (around 200 ml). Blow up the balloon and tie it down. You can also first blow up the balloon then put it on the bottle with water and just fill it.
- Light the candle and bring the balloon over it. The balloon won’t pop! If you try it with an empty balloon it will pop instantly.
The science behind the Burning the Balloon experiment
One of the amazing properties of water is its ability to soak up heat. The flame causes the water to heat up. That heated water rises and pushes the cooler layer down, so it gets heated in turn. That process happens rapidly and it prevents the heat from popping the balloon. This lasts as long as we don’t heat up all the water, so after some time the balloon will pop. One good real-life example of this is sweating! When our body is heated, we start to sweat. That is a defensive reaction of our organism, putting a layer of water on us and preventing overheating.
3. Pinning a Balloon
Materials needed for the experiment
- Balloon
- Yarn
- Pins
Instructions for the experiment
On a bed of many pins the pressure spreads out, and the balloon survives.
With distributed pressure, we can even put a balloon on pins.
- Blow up the balloon and tie it down.
- If you try putting it on one pin it will pop. Put many pins on the surface (sharp part up) and then try to put the balloon on top of it. It won’t pop!
The science behind the experiment
This is a great experiment to demonstrate one of the findings of Classical Mechanics - distributed pressure. When we put the balloon on one pin, the pressure is concentrated on one spot and it’s easy to break a thin layer of the balloon. However, if we distribute that pressure over the many points on the balloon, the force of any of them is too small to burst the balloon.
4. Balloon on the Stick
Materials needed for the balloon on the stick
- Balloon
- Yarn
- Wooden skewer
- Dishwashing liquid
Instructions for the balloon on the stick experiment
With a drop of dish soap, a skewer slides through the balloon without popping it.
With the right technique, we can even pierce the balloon without popping it!
- Blow up the balloon (not fully) and tie it down.
- Look at the balloon and identify areas where it’s darker (rubber is thicker). One spot is right where you tie down the balloon and the other is on the opposite side.
- Coat the wooden skewer with dishwashing liquid (you can also use vaseline) so it feels smooth.
- Pierce the balloon on one of the spots we previously identified and push it in. Let it come out on the other spot, on the opposite end. You now have a balloon on the stick!
The science behind the balloon on the stick experiment
A balloon is made of rubber, and that rubber consists of long chains of polymers. Blowing up the balloon stretches these polymer chains, and the rubber is then under tension, pulling tight in every direction like a stretched elastic band.
But it is not stretched evenly. The rubber is thickest at the very top and right around the knot, which is why those spots look darker, and thick rubber stretches less. So the tension there is much lower. Everywhere else the rubber is thin and pulled tight, and a hole in tight rubber tears open instantly - that is the pop. At the two low-tension spots, the rubber is relaxed enough to close around the skewer instead of ripping, and the balloon survives.
5. Demonstrating Centripetal force
Materials needed for demonstration
- Balloon
- Yarn
- Coin
Instructions for demonstrating centripetal force
A coin spinning inside the balloon makes centripetal force visible.
With the coin and the balloon, we can even demonstrate and learn about centripetal force.
- Insert the coin inside the balloon. Try to push it as far as you can, but it doesn’t have to go all the way in.
- Blow up the balloon and tie it down.
- Shake the balloon in a circular motion. You will see the coin spinning.
- Stop the motion and the coin will continue its movement for some time.
Warning: this activity is addictive! 😄
The science behind the centripetal force experiment
To move anything, including our coin, we need to input some energy. In this case, our original circular shaking of the balloon supplied needed kinetic energy. The round shape of the balloon forces our coin to move in a circular way, otherwise, it would continue moving forward**.** There is not that much friction between the coin and the surface of the balloon, so the coin moves for a long time after we stop the motion. But, in time, friction and gravity force out the coin to halt.
The important force here is the centripetal force. This is a centre-seeking force: it acts on our coin and constantly changes its direction so it keeps going in a circle. Left alone, the coin would fly off in a straight line, so something has to keep pulling it back towards the middle.
So what is doing the pulling here? It is the balloon wall itself. The rubber is curved, and as the coin presses outward against it, the wall pushes straight back inward on the coin. That inward push is the centripetal force, and it is the only reason the coin curves around instead of shooting off.
Friction has a different job. It is the grip between the coin and the rubber, and it is what makes the coin roll and spin rather than slide about. There is not much of it, which is why the coin keeps going for so long after you stop moving your hand.
The same idea works far beyond balloons, just with a different force doing the pulling. For the Moon going around the Earth, it is gravity that plays the centripetal role. For a ball on a string, it is the string.
🔬 Make it a real experiment
Take the fireproof balloon (experiment 2) and turn it into a measured test. Fill three balloons with different amounts of water and, holding each over the flame with an adult, time how long each lasts before it pops. More water should mean more seconds, because there is more of it to soak up the heat. Keep the flame and the distance the same, so the only thing you change is the amount of water.
Key takeaways
- Blow up a balloon with an acid-base reaction: vinegar + baking soda make carbon dioxide gas that inflates the balloon.
- Fireproof balloon: water inside soaks up the flame's heat, so a water-filled balloon won't pop over a candle.
- Balloon on pins: spreading the force over many pins means no single point can pierce the rubber - distributed pressure.
- Balloon on a stick: pierce it at the least-stretched spots (top and knot), where the rubber is thickest and under the least tension.
- Spinning coin: the round balloon forces the coin into circular motion, a hands-on demo of centripetal force.
Frequently Asked Questions
How do you blow up a balloon with baking soda and vinegar?
Pour vinegar into a bottle, add baking soda to a balloon using a funnel, then stretch the balloon over the bottle's mouth and lift it so the soda drops into the vinegar. The acid-base reaction produces carbon dioxide gas, which expands and inflates the balloon.
Why doesn't a water balloon pop over a flame?
The water inside absorbs the heat from the flame before the rubber gets hot enough to burst. Warm water rises and cooler water takes its place, carrying heat away. An air-only balloon has nothing to soak up the heat, so it pops instantly.
How can a balloon rest on lots of pins without popping?
It's about distributed pressure. On a single pin, all the force is concentrated on one point and easily pierces the rubber. Spread over many pins, the force on each point is too small to break the balloon's surface.
Where should you pierce a balloon so it doesn't pop?
Push a lubricated skewer through the darker areas - right by the knot and at the very top - where the rubber is thickest and the polymer chains are least stretched. There, small holes don't create enough tension for the balloon to burst.
Are these balloon experiments safe for kids?
Most are very safe, but experiment 2 uses an open flame, experiment 3 uses sharp pins, and experiment 4 uses a skewer. These need adult help and supervision, with water kept nearby whenever the candle is lit.
What science do balloon experiments teach?
They cover a lot of ground: acid-base chemistry, heat capacity, air pressure and density, surface tension and polymers, and centripetal force. Balloons make these abstract physics and chemistry ideas visible and fun to explore.
We hope you enjoyed these fun balloon activities. And if you’re searching for more fun STEM experiments that kids will love, you can demonstrate osmosis using gummy bears. Or if you want to see how to raise the water using a candle, check out the candle in the vacuum experiment. And some other similar experiments we would like to recommend are demonstrating light bending and making a dancing grain experiment. Happy learning!
