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Fire Extinguisher

Target Audience
Middle/ Upper Key Stage 2

Link to the National Curriculum
Sc4 Physical Processes (Materials)

Children should be taught to:

“explain that some changes result in the formation of new materials and that the kind of change is not usually reversible, including changes associated with burning and the action of acid on bicarbonate of soda.”


  • To demonstrate to children that when ingredients are mixed together new materials are formed and very often the changes are not reversible because a chemical reaction has taken place

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What you need

  • Re-sealable plastic bottles,
  • sodium bicarbonate ( baking powder),
  • acetic acid (vinegar),
  • candles,
  • plastic funnel,
  • spoon and
  • safety glasses.

What you do

  • Watch the video clip “The Fire Extinguisher” from the website: practicalprimaryscience.co.uk
  • Place two or three spoonfuls of baking powder into the bottle by way of the funnel ( the amount used is dependent on the amount of vinegar and will only be established by trial and error before allowing the children to perform the investigation).
  • Make sure the re-sealable cap of the bottle is fully closed, before pouring in a small amount of vinegar by way of the funnel and replace the stopper.
  • Give the bottle a small shake, once sealed, to encourage the chemical reaction to take place
  • Light the candle, place it in a safe environment and make sure all involved are wearing safety glasses.
  • Hold the bottle approxsix inches from the lighted candle and release the re-sealable stopper.

How it works

  • The vinegar reacts with the baking powder and starts a chemical reaction which produces a white powder called sodium acetate and also produces water and carbon dioxide. This reaction is not reversible meaning that the original ingredients have been changed and cannot return to their original form

Group / Class Organisation

  • Depending on the number of additional adult helpers will determine how many groups of three/four children can take part at any one time
  • Clearly as this activity is not without hazard it is very important that all those involved wear safety glasses, the school safety policy is observed and that all children are made completely aware of the potential hazard should anyone act in an inappropriate way

Preliminary activity

  • The work of the Fireman usually takes place in the lower classes with Topics/Themes such as “People who help us”
  • Other topics include: The Postman, The Policeman, The Doctor, The Nurse etc. These Topics more allows for further investigatory work of a simple nature and provides a natural follow-on for the children to understand the world around them.

Follow up work

  • This investigation provides an ideal opportunity to introduce the children to basic chemistry.
  • By this time, in any case most will be familiar with the chemical formulae for water and oxygen and this is just a natural progression to understanding the world around them.
  • One chemical formula for the Fire extinguisher:
  • NaHCO3+ CH3COOH = NaCH3COO+ H2O+ CO2
  • *CO2 is the chemical formula for carbon dioxide. Carbon dioxide is heavier than air and so it smothers fires not allowing air, its life blood to get to them.
  • Other follow up work could include an investigation into the composition of air to demonstrate that air comprises 4/5 Nitrogen and 1/5 Oxygen.

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