observation

Floating Cups

Submitted by rkrampf on Mon, 05/24/2010 - 22:09

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Slow Connection High Speed Flash High Speed Quicktime

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Submitted by rkrampf on Fri, 04/09/2010 - 15:22

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Strange Flame, part 1 - FREE -

Submitted by rkrampf on Wed, 01/13/2010 - 23:06

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What's Burning? - FREE -

Submitted by rkrampf on Sat, 12/26/2009 - 00:50

Anonymous:

Well, it is December, which means that I am rereading one of my favorite science books, Michael Faraday's "A Chemical History of a Candle." Faraday was a marvelous teacher, and his lectures were amazing. Sticking with the candle idea, we will take a close look at how they burn. You will need:

- a candle
- a match or lighter to light the candle
- a candle holder

Since we are using fire, be sure to get permission, and be sure that there is an adult there , so you have someone to blame in case something goes wrong.

Place the candle in the holder and light it. Now get comfortable and watch the flame for a minute. Take the time to really observe what is happening.

OK, now for the question. What is burning? The candle. OK, but what part of the candle? Your first instinct is probably to say that the wick is burning, but is it? Take another long look, and you will notice that although the flame is coming from the wick, the wick is not burning up. Instead, the wick seems to stay the same length, even as the candle burns shorter and shorter. How can that be?

If the wick is not burning, then what is? The candle wax. Notice that there is a pool of melted wax around the base of the wick. That melted wax soaks up into the wick, just as water soaks up into a paper towel. It is the melted wax, not the wick that is producing the flame.

So, does the wick not burn? If it did not, then as the candle burned shorter and shorter, the wick would stay the height of the original candle. Take another close look at the candle flame. You should notice that the wick is curved, and at the point where it gets close to the outside of the flame, the end of the wick is glowing. In the center of the flame, there is very little oxygen, so the wick does not burn. As the wax burns down, the end of the wick gets near the oxygen rich air at the surface of the flame, so that part burns away. That keeps the wick the same length, as the candle burns lower and lower.

I always look forward to holidays and birthdays, because they are perfect times to pause and enjoy the incredible science involved in the simple act of burning a candle. Yes that is the reason. It has nothing to do with all the pies, and cakes, and cookies, and egg nog, and ice cream, and ..., well, maybe that too, but I definitely enjoy the candles while I am eating.

Have a wonder-filled week.