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Home-Made Fire Extinguisher

This experiment isn’t recommended in an emergency – call 000 first and try the science later!

Australian Curriculum links

  • Science > Chemical Sciences > Year 5 > ACSSU077
  • Science > Chemical Sciences > Year 6 > ACSSU095
  • Science > Chemical Sciences > Year 8 > ACSSU225
  • Science > Chemical Sciences > Year 9 > ACSSU179
  • Science > Chemical Sciences > Year 10 > ACSSU187

You’ll need

  • Large clear jug
  • Bicarbonate Soda
  • Vinegar
  • Candles
  • Matches

Try this

  1. Place about 1/3 of a cup of bicarbonate soda in the jug, and add the same amount of vinegar. The mixture will bubble and fizz.
  2. Light the tea-light candles.
  3. Once the fizzing has stopped in the mixture in the jug, carefully pick up the jug and carefully pour it over the candles, without pouring out the liquid. The candles should go out.

Further investigation

  • Instead of pouring out the carbon dioxide, try blowing soap bubbles into the jug. You should see the bubbles appear to float on “nothing”, but really they are sitting on top of the invisible carbon dioxide layer.
  • Try pouring the carbon dioxide into an empty jug and then pouring it over a candle flame. This can make the experiment look much more impressive if performing it for an audience
  • This experiment is just one way to create carbon dioxide. You could also use dry ice, which is solid carbon dioxide (around -80°C) that sublimes into carbon dioxide gas. Dry ice can be purchased easily from industrial suppliers like BOC, but you should ensure you appropriately risk assess its use before taking it into a classroom.

What’s happening?

A chemical reaction occurs when bicarbonate of soda and vinegar are mixed together, which produces carbon dioxide (CO2) gas. This gas can be poured from the jug like water. CO2 gas is denser than air, so when it is poured from the jug, it sinks down on top of the candle like a blanket, pushing the oxygen out of the way. Flames need oxygen to burn. Without it, they will quickly be extinguished.

Real world links

CO2 fire extinguishers are often used in situations where it would be dangerous to put out a fire with water (such as electrical fires). In these cases, the extinguishers are loaded with pure carbon dioxide gas which is stored under pressure. A 5kg CO2 extinguisher will release almost 3000L of carbon dioxide gas in less than a minute when fully discharged.