Candles in a bell jar

To Do and Notice

Mount three or more candles on a set of stairs so that each candle is and inch taller than the one below it.

Cover the candles with a glass jar.

Notice that after a while the top candle goes out, followed by the next one down. The candles go out one by one from top to bottom.

What's Going On?

The candles burn oxygen and create carbon dioxide. While carbon dioxide is heavier than air at the same temperature, the carbon dioxide produced by the candles is hot and so rises to the top of the glass jar. As the candles burn the top of the jar fills with carbon dioxide. When the carbon dioxide reaches the candles they go out one at a time.

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Scientific Explorations with Paul Doherty

© 2000

1 Feb 2000