Dr. Gadget's Science Machine
A flame is more than just heat
A fun look at science working in the world around you, plus a cool gadget or experiment to test it out
By Dr. Gadget
Aloha! For the last few weeks we've been talking about light, so today let's talk about candles. Why are candles used to celebrate birthdays?
Jeff Widener • The Honolulu Advertiser
The Web turned up some interesting facts. The Greeks placed candles on cakes they made for the moon goddess they called Artemis. They thought candles made the cakes look like the glowing moon.
Heidi Cortez and Ryan Kuwazaki at Moanalua Middle School demonstrate using a candle and soda cans to see what a flame is made of. An adult should help with the experiment.
Germans sometimes used only one large candle with 12 divisions. It was re-used each year and symbolized the "light of life." Of course, you probably know the tradition that says that if you make a wish and blow out all of the candles with one breath, your wish will come true.
Candles date back to 3000 B.C. in Crete and Egypt. Clay candle holders have been dug up as evidence of this. The "modern" candle probably came into being in the 13th century. Back then, candles were all hand-dipped and made from beeswax and tallow.
Molds came into use in the 15th century. Finally, in the 1800s, candle-making became mechanized with the invention of braided wicks, molding machines and the discovery of steric acid to harden wax.
What causes the candle's flame? Is it made of some material? Here's a simple experiment to explore these questions, but you should have an adult help you:
1. Get a birthday candle and attach it to a piece of cardboard that you can later throw away. The candle can be attached by lighting it and allowing some wax to drip onto the cardboard. Before the wax hardens, blow out the candle and set the bottom of it into the melted wax. Hold it there until the wax hardens.
2. Now find an old soda can. Make sure it is empty. If you were to light the candle and hold the soda can into the flame, what do you think would happen to the soda can? Yes, it would get warm, but what else? Pull up the tab on the top and hold it with the tab into the candle flame. What happened? Did the can get black stuff on it? What is that black stuff? It's the flame! The flame is made of some kind of solid material!
The black stuff is carbon. Anything that burns usually contains carbon. Black ash is leftover carbon. If food burns on the stove, it turns black — more carbon.
Why is carbon in the flame? It is unburned fuel. It is also what gives the flame its golden-yellow color. How? The heat of burning excites the electrons in the atoms of carbon, causing them to move to a new position away from the nucleus of the atom. But the electrons do not want to remain there. When they go back to their regular positions, they give back the excess energy, but not as heat. They convert the heat to light!
Anything that makes its own light, from a light bulb to a glow light stick, does it this way. The only difference is the starting energy. A light bulb uses electricity while the glow light stick uses the energy from two chemicals mixing. In either case, electrons are excited by energy and forced out of their normal positions around the nuclei of their atoms. When the electrons return, they give off light.
More on light next time. Until then ... a hui hou!
Write to Dr. Gadget care of The Honolulu Advertiser, P.O. Box 3110, Honolulu, HI 96802, or fax 535-8170. You may send e-mail to ohana@honoluluadvertiser.com only if you're 13 or older.
"Dr. Gadget's Science Machine" is written by Joe Laszlo, a retired science teacher and winner of a Presidential Award for Excellence in Science Teaching. His column alternates in this spot with "Hawai'i Nature Squad."
