by STEM Scouts
This popular, citrusy experiment offers up both science and a snack. Adult supervision is required.
- Olive Oil
- Pairing Knife
- With the pairing knife to carefully cut the orange around the circumference of its center, not from end to end. Be sure to only cut through the rind, or peel, of the orange and not into the carpel, or fruit.
- Gently remove half of the rind from the carpel and ensure the central column, or stem, is intact.
- Once you’ve removed the half, which should look like an upside-down mushroom or umbrella, fill it with olive oil. Make sure some of the oil gets on the central column.
- Using a match or lighter, light the central column as though it were the wick of a candle. It may take a moment to catch fire.
- For added safety, you can place the candle in a small bowl so it doesn’t spill over.
How Does It Work?
This is a shortened version of How Stuff Works’s explanation of candles, read the full entry here.
There are two parts that work together in a candle: the fuel, made of some sort of wax, and the wick, made of some sort of absorbent twine.In the case of our orange, the olive oil is the wax and the wick is the central column, which supports the walls between each segment.
When you light a candle, you melt the wax in and near the wick. The wick absorbs the liquid wax and pulls it upward. The heat of the flame vaporizes the wax, and it is the wax-vapor that burns. The reason the wick does not burn is because the vaporizing wax cools the exposed wick and protects it.
Paraffin wax will burn on its own, but it is like cooking oil, motor oil and coal in that you have to get it very hot for combustion to begin. An oil fire is intense and very hard to put out. Paraffin is the same way. In a candle, this works great—only the tiny amount of wax on the wick is hot enough to vaporize and burn.