As many households with young kids, we have A LOT of old crayons. For some time I’ve wanted to recycle our old broken crayon by melting them. I had several Ikea rubber ice trays, and with Valentine’s day approaching, I thought we could use our old crayons to make a goody for my sons’ classmates. I found this activity with instructions on melting crayons, and after following the instructions, I had some unexpected results!
The Science Behind Melting Crayons – A Valentine’s Day Science Experiment
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Supplies:
Broken Crayons
Rubber ice tray from Ikea
Meat Thermometer
We followed the instructions just as they were described in the post I found. But instead of combining all the colors, we separated the colors. We were also curious about the melting temperature of the crayons, so I borrowed my husband’s grilling thermometer. I heated up the thermometer tip, and stuck it into the end of a crayon. Sticking the thermometer into the crayon ensure we would be reading the temperature of the melting crayon, instead of the temperature of the oven.
We placed the crayon and thermometer into the ice tray, then placed everything into the oven.
We opened the oven once a minute to check if all the crayons were melted.
But as time passed, we realized it was taking longer than we expected. We started checking every few minutes, and removed the ice try from the oven once most of the crayons were melted. What we pulled out was not what we expected!
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While the red and white crayons were completely melted, the pink crayons were only partially melted. Our results made us think that each color of crayons has a different melting point.
Once the crayons were solid again, we removed them from the ice tray, and noticed the crayons had two layers to them. The top layer was wax, and the bottom layer felt and wrote like chalk.
What happened?
Crayons are made of two ingredients: paraffin wax and color pigment. During the process of heating up the crayons, the two ingredients separate. When two liquids separate, lower density liquid floats to the top. Since the wax is on the top, we know the density of the wax is lighter than the density of the color pigment.
Our results were consistent with each color we created.
Because of our unexpected results, my son and I came up with a list of more experiments we would like to do with our crayons. Here’s the list we came up with:
-Find out how to make crayons without the wax/pigment separation
-Measure the melting points of different pigments such as white, pink, and red
-Find out the density of different crayons
What other crayon experiments can you come up with? I’d love to know your suggestions!
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