Watch a styrofoam cup disappear before your eyes! You can find acetone at a hardware store, or buy it in a small quantity from us. It is very flammable, so keep it away from all flames and use it in a well-ventilated area. This project requires adult supervision.
How to Make a Styrofoam Cup DisappearDisappearing Styrofoam CupHome Science Tools
>> Watch our video demonstration below, then try it yourself!

What You Need:

What You Do:

  1. Set the cup in the middle of the pie tin
  2. Carefully pour about a tablespoon of acetone into the cup.
  3. Watch the reaction!

What Happened:

Styrofoam is mostly air, trapped in place by the polymer polystyrene. A polymer is a very large molecule formed by repeated patterns of chemical units strung together in long chains. The acetone dissolves the long polymer strands in the styrofoam, allowing all the trapped air to escape. Without air, the cup is just a blob of polystyrene on the bottom of the dish! You can pour off the excess acetone and let the blob of polystyrene dry into a hard lump of plastic.

Note: This project makes a great lab safety demonstration: A teacher can pour water into a styrofoam cup and drink it, then pour acetone (which looks like water!) into the cup. Hold the second cup over a bowl or beaker to contain the mess. Use this to reinforce that one should never eat and drink in a lab. What looks like water may be something quite different!

Watch Disappearing Styrofoam Cup