· bicarbonate of soda
· heatproof bowl
· short candle
· playdough or modelling clay
· dessert spoon
· an adult, to supervise lighting the candle with the match
1. Use the modelling clay to fix the candle firmly in the centre of the bowl.
2. Put five level dessertspoons of bicarbonate of soda around the candle.
3. Light the candle.
4. Spoon vinegar slowly down the inner side of the bowl, avoiding the flame. What happens when the liquid and powder mix?
5. Stop adding the vinegar when the froth is about halfway up the candle.
6. What happens to the candle? (Here’s a clue – what happens when you try to relight it?)
Fizzy candle – the science
· New substances are made when the bicarbonate of soda and vinegar are mixed together.
· One of these substances is a gas called carbon dioxide. This is the same gas that makes the bubbles in fizzy drinks. Here, it causes the mixture to froth.
· Carbon dioxide is heavier than air. It fills the bowl, even though you can’t see it.
· But the candle needs air to stay alight, so when the bowl is filled with carbon dioxide, the candle goes out.Because of this, carbon dioxide is used in many kinds of fire extinguisher