Hands-on science: Fizz Bang
Fizz Bang
The original pocket rocket
Here's how to fire a plastic pot metres into the air. Challenge your friends: whose goes highest?
One person can do this, but working quickly is important so helping hands are good. Besides, you'll want people to see how your rocket flies.
Download the Fizz Bang PDF(398 Kb). Adobe Acrobat is required.
Step by step
Yan's video guide
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Dr Yan shows you how to try Fizz Bang safely
Checklist
| Difficulty: low | Simple once you get the right container |
| Time/effort: very quick | Takes under a minute, but the fun's addictive |
| Hazard level: low | Stand back and don't aim them at people |
SAFETY: Do this outdoors on level ground where there's nothing breakable above you.
Children especially should wear eye protection. Use safety specs or ordinary (sun)glasses as long as they have lenses made of plastic.
You need
A plastic tub with a tight fitting lid and no sharp corners. The plastic canisters that camera film comes in are ideal, if you can find one
Fizzy tablets, such as 'effervescent' vitamin tablets or hangover/upset stomach remedies
Tap water
What you do
Launching from a level, hard surface is best
Put water in the tub so it's about one quarter full.
Break a fizzy tablet roughly in half.
Get the lid of the tub ready.
Drop the piece of tablet in the water and snap the lid on as quickly as you can.
Put the canister - lid downwards - on the ground.
SAFETY: step back at least one metre.
What should happen
After quite a bit of fizzing the tub will fly off. It should go several metres up into the air.
The lid stays behind and you may also see the sludgy remains of the tablet still fizzing away on the ground.
If it doesn't work for you
The tub and lid are the main thing to check. Make sure water or gas isn't seeping out. You'll see bubbles on the outside if the lid isn't a good enough seal. Try a different kind of canister if it does leak.
You can also improve the rocket's performance by using different sorts of tablet and by adjusting the amount of water and of tablet. If there is any tablet left behind afterwards, fizzing on the ground, you know there's no point using a bigger piece.
What's going on
A build up of gas
Rockets, jets and propellors all work by pushing something away in one direction (usually backwards). Doing that gives the craft itself a push in the opposite direction (that'll be forwards).
Here, when the pressure inside the tub is enough to push the lid off, the force of the gas escaping downwards gives the tub a mighty shove upwards.
What generates the pressure? Effervescent tablets and powders often contain sodium bicarbonate and citric acid. Added to water, they mix to produce bubbles of colourless carbon dioxide gas.
The carbon dioxide mixes with the air contained in the tub. With more and more gas building up - in a volume that can't increase - the pressure inside the plastic tub rises.
More rocketry
The physics that launches the Fizz Bang tub skywards is similar to what propels Water Bottle Rockets upwards. Yan has made an activity guide to show you how to make those as well.
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