Candles may smell nice and look great at Christmas time, but they can also teach you a lot. These wax sticks produce heat, change shape when they burn and interact with the air around them. By lighting a few candles, you can learn important scientific principles by simply watching the flames flicker.
When working with candles, handle them carefully to avoid getting burned or starting a fire. Ask an adult to perform these experiments if you don't feel comfortable doing them.
No Air, No Fire
The scientist Robert Boyle proved that combustion cannot occur in a vacuum -- air must exist around an object for it to burn. Verify this by observing how candles burn in different amounts of oxygen. Place three identical candles in holders on a table and light them. Place a large jar over one candle and a medium-sized jar over another. Ensure that both jars are large enough to enclose the candles and holders. The candle with the smaller container goes out first because less oxygen exists in that container. The candle with the larger container goes out next, and the uncovered candle extinguishes last since it has the air around you to use as fuel.
The Intriguing Seesaw Candle
This experiment shows what happens when an object's center of gravity shifts. Push a darning needle through a cork and stick a candle on each end of the needle. Push a long knitting needle through one side of the cork so that it and the candles form a cross shape. Place two small glasses upside down on a piece of aluminum foil and balance the candles and darning needle on the glasses. When you light the candles, they swing back and forth like a seesaw. This happens because as wax drops from one candle, the center of gravity moves to the other candle, causing it to become heavier and move down.
Blow Out a Candle with Science
Learn about carbon dioxide by extinguishing a candle mysteriously. Place a short candle inside a small glass and put a heaping spoonful of baking soda in a large glass. Add a third cup of vinegar to start a reaction that produces carbon dioxide gas and foam. Place a 3-by-5-inch note card over the glass to ensure that the foam remains inside the glass. Hold that glass over the smaller one and gradually tip the larger glass, stopping when the vinegar reaches the rim. The candle goes out because the invisible carbon dioxide gas in the larger glass falls onto the candle and extinguishes the flame.
Fun with Air Currents
Stand behind a round object, such as a tree trunk, and wind blowing from the other direction still strikes you. Learn why this happens by placing a lit candle behind a bottle and blowing against the bottle. The candle goes out because air you blow splits when it strikes the bottle and moves along its curved sides. When the air reaches the other side, it converges and puts out the candle.
- 101 Hands-On Science Experiments; Phil Parratore
- The Little Giant Book of Science Experiments; H. J. Press
- Groundbreaking Scientific Experiments, Inventions, and Discoveries of the 17th Century; Michael Windelspecht
- The Everything Kids' Magical Science Experiments Book; Tim Robinson
- Science Experiments; H. J. Press
- Photo Credit petrograd99/iStock/Getty Images
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