What you will need:
- Styrofoam cups (various sizes)
- Rubber bands
- Small weight
- Pan for boiling water – Use extreme caution!
- Adult supervision
- Fill a large sauce pan with enough water to completely submerge your Styrofoam cup. Have an adult place it on the stove and bring the water to a rapid boil.
- Place several rubber bands around the outside of your cup.
- Place your weight inside the cup.
- Have the adult use the tongs to slowly place your cup into the boiling water keeping it upright so that the weight stays in the cup as you completely submerge you r cup into the water. Remember that the water is boiling and can be very dangerous.
- You will notice that your cup will begin to be compressed where the rubber bands are wrapped tightly around the outside of the cup. Once your cup looks like it is the shape you want, have the adult carefully remove the cup with the tongs and carefully empty the boiling hot water out of the cup. Use caution so that the weight does not drop out of the cup causing the hot water to splash on anyone. Also remember that the weight has been in the boiling water and will remain extremely hot for quite some time. Do not touch it until it has completely cooled.
- Remove the rubber bands and enjoy your creations.
What is going on?
Styrofoam cups are made from polystyrene plastic, which has thousands of small air pockets throughout its structure making them an excellent insulator. We can change the form of the cups by placing them into the rapidly boiling water and heating the polystyrene plastic to a point where it becomes soft and mold-able. Since the rubber bands are stretched tightly around the outside of the cup, this creates pressure in these areas causing the cup to deform. Since Styrofoam is extremely buoyant, we must add enough weight to hold the cup down under the water in order to properly heat it enough for this to work.
If you have a pressure cooker, try placing a Styrofoam cup on a tray inside the pressure cooker for about 10 minutes. Make sure that there is enough water inside the pressure cooker to last the 10 minutes but not enough to touch the cup itself. As always, please use extreme caution when doing this or any experiment and follow all manufactures instructions and cautions when using your pressure cooker. You do not need to place rubber bands around the cup for this experiment as the pressure cooker will heat the cup while the intense pressure will force the small gas pockets to be released from the Styrofoam causing it to shrink making a miniature cup.