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Melting Styrofoam Heads with Acetone!

Styrofoam is all around us. It has become one of the most common insulators and packaging materials in the world. Styrofoam coffee cups keep our drinks warm, packing peanuts keep our valuables safe in shipping, and it even keeps our drinks nice and cool inside our cooler on a hot day. Why is styrofoam so popular?

What is styrofoam?

Styrofoam is an extruded polystyrene foam that is trademarked by the Dow Chemical Company. It is actually polystyrene that has had air pumped through it to increase the amount of air bubbles in the polystyrene. What is polystyrene? First let's dissect the name. Poly means many and styrene is a name for the compound that gives the styrofoam structure. Styrene is an organic compound (C6H5CH=CH2) that is a colorless, oily liquid that evaporates very quickly. Single styrene chains of molecules are called monomers of styrene (mono means one). When many monomers are put together they are called polymers (remember poly means many). So, polystyrene is a series of long organic (carbon based) molecules, that, when forming consist as in a liquid state (think of a puddle of white glue).

To turn this into styrofoam, the makers pump air into the mixture to make small beads of polystyrene and, as the foam balls are turning to a solid, they mixed together and formed into a shape like a cup, packaging material or a cooler.

Why is styrofoam such a good insulator?

Styrofoam is an excellent insulator meaning that it resists changing temperature. Air is a good insulator. Think about your windows in your house. If you have a double pane window, the air in between each pane resists changing temperature. If it is cold outside, the air gap keeps the warmer air from mixing with the cooler air - thus keeping your house warm. The same is true with styrofoam. The small air bubbles in the foam resist changing temperature. So, your hot coffee in the foam cup stays warmer longer because the pockets of air are keeping it from interacting with the cooler air outside the cup.

Why does acetone melt styrofoam?

Experimenting with melting styrofoam in acetone
Melting a tower of styrofoam in acetone

Styrofoam dissolves in acetone, it doesn't actually melt - melting requires heat. So, the correct question is: Why does acetone dissolve styrofoam?

Remember that polystyrene is made up of many smaller molecules called monostyrene. The acetone (formula (CH3)2CO) breaks the bonds that hold the polystyrene together. And, because styrofoam is mostly pockets of air, when the bonds are broken the air can escape. As the air escapes the volume of the styrofoam decreases. The foam doesn't disappear, it turns into a liquid, mostly void of the air that made it so valuable as an insulator. Just to prove how much air is in styrofoam, I decided to see if it was possible to dissolve 7 feet of styrofoam in acetone! Was I successful? Watch the video and prepare to have your face melted with science! (That is just an expression - I don't intend to melt 'real' faces with science!)

How to dissolve styrofoam in acetone.



*Acetone is flammable and harmful to skin/eyes - use appropriate protection*

Let the acetone come into contact with the styrofoam! You will see the magic unfold in front of your eyes!

  • Experiment to see if different kinds of styrofoam dissolve at different rates.

  • Try melting biodegradable packing peanuts - you might be surprised at the result!

Keep on Learning!


Watch acetone melt styrofoam into a liquid mess
Melting Foam Heads with Acetone


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