Some gases are invisible and have NO odour, which can be dangerous for us oxygen breathing animals! Carbon dioxide, oxygen, nitrogen, hydrogen and carbon monoxide are common gases we need to be aware of.
This experiment shows you how carbon dioxide produced from a ‘classic’ chemical reaction can be used to put our flames.


  • invisible-fire-extinguisher-experiment-materialsBicarb of Soda
  • Vinegar
  • Tea light candles
  • Matches
  • Measuring jug
  • Spoon
  • Adult supervision!



1. Matches and fire = Adult supervision and assistance









  • invisible-fire-extinguisher-step 1Use the spoon to place some bicarb into the bottom of your measuring jug.
  • invisible-fire-extinguisher-step 2Pour the vinegar into the jug containing the bicarb.
  • It should fizz as a result of producing the CO2 (which fills the jug)




Place your hand over the jug to prevent spilling and concentrate the CO2 in the jug.


  • invisible-fire-extinguisher-step 4The adult should light the tea lights while step 2 is occurring.
  • invisible-fire-extinguisher-step-4Quickly pour (gently) over the top of the flames.
  • The invisible CO2 gas should pour out and fall onto the flame causing it to extinguish.


Check out the ‘Wacky Science’ video of this experiment and ‘What’s Going On’ series link. They are currently ‘In Production’, so check back soon…..

Wacky Science Ep

What's Going On?


For the candles to burn, three factors must occur which is usually seen in a combustion triagnle.

fire triangle

1) Fuel: The source of stored chemical energy that is being broken down. In our case it is the wax candle.

2) Ignition: A source of energy/heat/ignition is needed to start the burning (combustion) reaction. This usually is a spark etc

3) Oxygen: A burning reaction (called combustion) needs oxygen to continue.




For our candle, the oxygen surrounds the wick which is soaked in wax. Once started, the candle burns freely.




Oxygen gas and carbon dioxide gas are both colourless and odourless gases BUT carbon dioxide is heavier than oxygen.

The carbon dioxide falls over the flame and removes (displaces) the oxygen from around the flame and therefore the flame goes out. You have removed ONE of the factors needed to burn…. oxygen.

If you would like

– more details,

– pictures of the second half of the experiment

– information on how to investigate this further

– links to everyday examples

– management hints & teaching pointers (5P Teacher develpoment program)

 ….. then why not subscribe to one of the following


(1) Crazy science Club

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(2) 5P Teacher Training course called ‘Looney Lab  Classroom Creations

Looney Lab Classroom Creations2


Or you can purchase the ‘Bright Sparkes Guide’ of this demonstration only ($2.50) which has:

    • HD pictures of experiment steps
    • Detailed explanation of science
    • Mini-challenge section (another experiment)
    • Making it a ‘Scientific Method’ experience
    • Graphing opportunities
    • REAL links and descriptions to everyday examples of concept.