The invisible fire extinguisher

The explanation

If you’ve watched the video above, Candletastic – the invisible force, you might be puzzled. What put the candles out? Was it a gas? Was it a liquid?

You can try this at home – but remember don’t let children handle matches or candles, and don’t leave lit candles unattended.

The vinegar and bicarbonate of soda make a gas – carbon dioxide. This is heavier than air and so sits in the jug. When you tip the jug, it pours out.

Flames need oxygen to burn (which is present in the surrounding air) – but when the carbon dioxide pours over the flame it pushes the available oxygen out of the way and the candle can’t burn any more.

Take a look at a normal (red) fire extinguisher, many contain carbon dioxide… but with a bit more fizz.

What could you do next?

• Check out Science courses at the OU
• Post clips of your science experiments as video comments on the YouTube page of candletastic (though please – no dangerous ones)