You’ll need
- A wax candle
- A heatproof plate
- A lighter or box of matches
- A lightly boiled potato (make sure you let it cool)
- A knife or apple corer
- Some slivered almonds
What to do
- Gather your materials on a flat surface.
- Put the wax candle on the heatproof plate.
- Use the lighter or a match to light the wax candle. Watch what part of the candle burns.
- Blow out the wax candle and let it cool.
- Remove the wax candle from the heatproof plate.
- Carefully use the knife or apple corer to cut the potato into a candle shape.
- Push the end of one almond sliver into the top of the potato (to make the candle wick).
- Put the potato candle on the heatproof plate.
- Use the lighter or matches to light the tip of the almond sliver. Watch what part of the candle burns.
- Blow out the candle and let it cool.
- Eat the potato candle!
Questions to ask
What part of the wax candle burned? Was it the same part in the potato candle?
Try using other nuts as the wick in your potato candle, like peanuts, cashews and walnuts. Which nuts burn for the longest amount of time? Which nuts burn for the shortest amount of time?
What's happening
For a fire to burn, it needs energy (usually heat), oxygen and a fuel. For both candles, oxygen is in the air and the heat energy comes from the lit match or lighter. In a wax candle, the heat vaporises the wax, and this vapour (gas) is the fuel. In the potato candle, the fat in the almond is vaporised, and that is the fuel.
A candle is made of 2 parts: a wick and wax. The wax is often paraffin wax (a wax that comes from crude oil) or beeswax (a wax made by honey bees). The wick is made of an absorbent material, which means that the material soaks up liquid. When the wick is lit, the heat from the flame melts the wax near the wick. The wick absorbs the liquid wax, and the liquid wax moves up the wick. When the liquid wax reaches the flame, it turns to vapour. The wax vapour is the fuel that keeps the candle burning.
The potato candle is also made of 2 parts: the almond and the potato. Almonds are made of proteins, fats and carbohydrates. When an almond is lit, the chemical energy stored in these fats, proteins and carbohydrates is released as heat. Fat in particular has a lot of stored chemical energy. Because almonds have a high amount of fat, the almond can burn for a long time. The potato doesn’t burn or supply any fuel for the flame – it’s just something for the almond to sit in.
Did you know
Our bodies use something called cellular respiration to release the stored chemical energy in the food we eat. Some of this stored chemical energy is transformed into the type of energy that our cells can use to do work. The rest of the chemical energy turns into heat. Without this energy, we wouldn’t be able to run, skip, jump or perform fun science experiments. You can learn how much stored chemical energy is in your food by reading the nutritional information on the packet.
(Sound of bubbles popping)
David: Hi I’m David from the Questacon Science Squad and I love candles but you can’t eat them, can you? So they’re not really perfect. I want to show you today how to make a candle that you can eat.
You need:
- a piece of lightly boiled potato and
- some slivered almonds
(David places boiled potato on plate next to candle)
Now, what you’re going to do, grab some of your slivered almonds like that. Here we go.
(David pours some almonds on to the plate)
Take one of them and poke it into the top of your candle there, or your potato.
(David pushes an almond into the top of the potato)
And grab a lighter and light it on fire, watching it burn, there we go, almost.
(David lights almond candle)
And there you have it an edible candle.
Now to find out why our candle burns like this you can head on down to the Science Squad Website. I’ll see you next time.
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