Burning at Both Ends
Question: Can you make a seesaw out of a candle?
KIDS’ LAB LESSONS
Most people, when asked to imagine a seesaw, conjure up images of a playground with children sitting on either end of a large toy, bounding up and down, squealing with joy. For most people, and perhaps for you, this is their only experience with a seesaw. But in this experiment, you will be building your own seesaw, one that needs no outside help to keep rocking back and forth, can fit on your kitchen table, and is definitely not something children should be riding.
When a candle burns, it loses some of its wax, which melts and sometimes drips over the side. This can produce a big mess if it goes unnoticed, but in this case, that dripping is exactly what you want to see happen. You'll have to trim the bottom end of the candle, so that there is a wick on either end. Then, after you set up your balanced seesaw and light each end, the candle should rock back and forth as long as there is wax left to burn.
Long (10-inch) taper candle
Kitchen knife (to be used only by an adult)
2 straight pins
2 identical drinking glasses
2 small saucers
1. Ask your adult partner cut about ½ to 1 inch off the bottom of the candle so that the wick is visible. It should stick out of the bottom just like it does the top.
2. Using the ruler, find the center of the candle and push one pin into each side of the candle at that point.
3. Carefully rest the pins on each glass so that the candle balances. It might take a few tries to get it just right. It should rock back and forth slowly.
4. Place one saucer under each end of the candle.
5. Light one end of the candle and let it burn until it starts to drip. When it does, light the other end and watch the candle begin to rock back and forth. You are truly “burning the candle at both ends.”
“The universe is full of magical things, patiently waiting for our wits to grow sharper.”
—Eden Philpotts, English science-fiction writer
Questions for the Scientist
1. Why might it be important to light the ends of the candle one at a time instead of at the same time?
2. Imagine that you could place the candle high enough above the table that it would not touch the table if it tipped. How might the experiment change?
3. How might your results change if the candle were not uniform in shape, that is, thicker on one end, thinner on the other?