Blowing Up A Hydrogen Balloon
The Grand Finale
- Exploding Balloon More
- Liquid Nitrogen Cloud More
The Physics: The exploding balloons demonstrate that nothing can be taken for granted in science. If you buy a balloon from a vendor, it’s probably filled with helium. Helium is a gas like air; in fact, air has some helium in it. But helium is lighter that air. If you take the same volume of air and helium and weigh them on a scale, the helium would weigh less. This is because helium is less dense . Because helium is lighter that air, a helium balloon rises, just as an air bubble rises in more dense water. Hydrogen is another gas lighter than air; it’s even lighter than helium. Hydrogen, however, is not used in balloons and this demonstration shows why.
Helium is a special gas called a Noble Gas , which means it doesn’t burn. When a match is held near a helium-filled balloon, the balloon pops. That’s it. But when a match is held near a hydrogen-filled balloon: BOOM! a real explosion. This is because hydrogen burns very easily. It combines with oxygen to make water vapor. Even though both balloons look the same from the outside, there may be something very different on the inside.
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Scientific Method - Hydrogen Balloons
Balloons filled with different gasses are observed and described before and after being touched with a burning candle.
- Before doing the experiment, let the students know the balloons can be quite loud.
- Never , under any circumstances, transport balloons with hydrogen or hydrogen + oxygen in your car.
- Hydrogen is flammable.
Chemicals and Solutions
- Hydrogen gas
- Fishing line
- Candle on Stick
- Ten foot pointer with candle taped to one end
Fill 3 balloons of the same color. Fill one balloon with helium (or oxygen), another with hydrogen, another with a mix of hydrogen (2/3) and oxygen (1/3). Use fishing line and duct tape to suspend the balloons about 10 feet in the air and at least 3 feet apart, either from the floor or from a table or lab bench.
The balloons are ignited with the candle attached to the pointer.
Demonstration Hints
Caution : the 2:1 mixture is very loud!!! and can shake the rafters.
First, students are asked to describe the balloons. Then, each balloon is popped using the candle on the pointer. Students are asked to observe and describe each event. Students are then asked to theorize about the balloons.
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Hydrogen balloon
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You feel the shock wave as the fireball of a hydrogen explosion rises from a recently-lit balloon. This demonstration is a truly spectacular, if slightly gratuitous, reminder of where the protons accelerated in the LHC are found.
1 × hydrogen cylinder 1 × hydrogen regulator with flashback arrestor 3 × balloons (helium-grade latex deflate slower) 3 × balloon weights string 1 × candle 1 × long stick 1 × lighter
This demonstration is both very hot and very loud. Be sure presenters wear eye and ear protection, that the audience is sat well back and that they cover their ears during the explosion. Also be aware of potential fire risks.
The demonstration
- Before the show, fill the balloons with hydrogen and attach them with string to the weights.
- Light the candle on the end of the stick.
- Standing well back, use the candle to light the balloon.
- Watch as a spectacular fireball ensues.
Vital statistics
reaction: 2H 2 + O 2 → 2H 2 O
adiabatic flame temperature: 2200°C
How it works
Hydrogen is used as a source of protons in the Large Hadron Collider. The simplest element, it is made up of just one proton and one electron, and that electron can be stripped off with electrostatic fields, leaving the proton to be accelerated in the collider.
A more visually exciting use of hydrogen is as a highly efficient fuel source: liquid hydrogen and liquid oxygen are used to create the huge controlled explosions which lift rockets off the ground and into space. Here, a balloon full of hydrogen and atmospheric oxygen are combined to make a slightly less controlled explosion. We often explode two of these balloons to close the show as well as the one which is strictly necessary for explanation early on!
- Adiabatic flame temperature (Wikipedia)
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