Did you know that you can play dominos with the flames of candles?
You will need:
Several thin candles such as birthday cake candles (as many as you have time to set up)
A sharp knife to cut the candles
A large glass bowl
A tray/flat non-flammable surface
Matches
Blu-Tack
Safety notes:
Be careful when cutting the candles!
This experiment involves fire and so should be done under the supervision of an adult.
What to do:
Cut the candles to different lengths so that you can line them up in order of height. Now use the Blu-Tack to stick them to the tray in height order. Light all of the candles and then cover them up with the glass bowl.
What to look for:
All of the candles will go out eventually. But they will go out in a particular height order. What is it?
What is going on?
You should have seen that the candles go out in order of tallest to shortest. If you did not see this, try repeating the experiment but with candles cut so that there is a larger difference in height between each candle.
The candles burn because air containing oxygen passes through their flames. They do two things to this air: Firstly they remove some the oxygen from the air. Secondly they heat the air. Hot air rises and so air that has been burnt by the candles collects at the top of the bowl. Because it has been through the candle flames, this air contains less oxygen than the cold air at the bottom of the bowl that has not yet been through any candle flames. For this reason the tallest candle is quickly surrounded by air that has less oxygen in it than air around the shorter candles. Therefore the tallest candle goes out faster.
This principle applies to all of the candles and so they go out in order from highest to lowest. Try building a really long candle run! |
