Invisible Fire Extinguishers

Explore energy in the context of the fire triangle with Abi, and see how a flame can be extinguished ‘as if by magic’ using CO₂ gas.

Making an invisible fire extinguisher is pretty amazing, and you can try this at home. But remember candles can be dangerous so please get help from an adult for this experiment and any other that involves fire.

What you will need:

• Vinegar
• A spoon
• Bicarbonate of soda 
• Tealights 
• A glass  
• Matches

What to do:

1. Pour 50ml of vinegar into a glass, then add 3 teaspoons of bicarbonate of soda to the vinegar and give it a stir. You will notice a chemical reaction will take place, creating bubbles. These bubbles are filled with carbon dioxide. Set aside the glass.
2. Light your tealights with a match.
3. Tip the glass gently over your lit candle, keeping the vinegar inside the glass. You are not pouring out the liquid, you are pouring out the gas.

Watch how your candle extinguishes as if by magic!

What is happening:

When vinegar and bicarbonate of soda are combined, the reaction creates carbon dioxide and water.  Carbon dioxide will rise to the top of the mixture, just like the bubbles in fizzy drinks. Carbon dioxide is much denser, or heavier, than air and so it will collect in the glass.

When you tip your glass, you are pouring the carbon dioxide over the flame, cutting off its supply of oxygen causing it to extinguish.