Why is polystyrene so light? Let’s break down some of the molecules and have a closer look!   

You will need:

  • Polystyrene cup
  • Acetone-based nail varnish remover
  • Pipette or teaspoon
  • Plate


  • Place the polystyrene cup on its side on the plate.
  • Use a pipette or teaspoon to carefully drip acetone around the centre of the cup only. Try and make a thin line of acetone all the way around the cup.
  • Watch the cup disintegrate, until you can pull and stretch it!

The Science Bit:

Polystyrene is a polymer, which means that if you had a very strong microscope, you would be able to see the molecules in long chains all linked together. When we use a solvent, in this case acetone, the polymer bonds or links holding the polystyrene together break down. Polystyrene contains a lot of air, which is what makes it feel so light, but when the polymer bonds are broken, all of this air is released, and only the polymer chains are left. So the polystyrene mass starts to reduce.

You could:

Continue to add acetone and see  how big – or small – your polystyrene cup ends up.    

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