Wanda the Melting Witch


To learn about polymers


  • Styrofoam® cup
  • Aluminum pan or glass bowl
  • Approx. 1 cup of pure acetone
  • Marker and construction paper (optional if you want to decorate your cup with a witch face and/or make a hat)
  • Stirring stick


Draw Wanda the Witch on your polystyrene cup. Make her hat if you desire too. Pour approximately one cup of pure acetone into the glass bowl or aluminum pan. Place the cup into the liquid. Push down using the stirring stick. What happens?


Wanda the Witch is melting! When acetone and polystyrene are mixed together the polystyrene dissolves into the acetone and creates sticky goo. Acetone breaks down polymers, the atoms that are the building blocks of plastic. Polystyrene holds millions of little pockets of air.  As the polystyrene dissolves, the air is released and sticky, stringy goo is created. When the sticky goo hardens it doesn’t have pockets of air anymore.

This activity requires adult supervision. Rubber glove and goggles are recommended too. Familiar household uses of acetone are as the active ingredient in nail polish remover and as paint thinner.