What is plastic?
  • Plastic is made from natural things that have long chains of molecules like wood, milk, cotton and coal but itís usually made from crude oil.
  • The long chains of molecules are called polymers.
  • Crude oil is heated and refined to make lots of products including Naphtha which you make petrol and plastic out of.
  Did You Know?
  • The first plastic was made out of milk. This kind of plastic is called casein.
  • Plastic was only invented 130 years ago.
  • Thermosetting plastic is as hard as rock and canít be recycled. This kind of plastic has a triangle on the bottom with the number 4 in it.
  • But thermoplastic can be re-heated and recycled and will have 1, 2 or 3 in the triangle.
  • If you know when you put water that is hotter than 85 in plastic fizzy bottles they shrink and change shaper permanently.
Use chocolate buttons to experiment how plastic can be moulded.

What you need:
The help of an adult
A packet of cooking chocolate or chocolate melts
A wooden spoon
A teaspoon
An ice cube tray
Or the plastic tray from inside a chocolate box
Or a chocolate mould tray if you have one

What you do:
Get an adult to help you melt some of the chocolate following the instructions on the packet. Stir the lumps with a wooden spoon to make sure all the lumps have melted. Use the teaspoon to put the melted chocolate into the ice cube tray or the tray from inside a chocolate box or the chocolate mould tray, and let the chocolate set.
When itís set tip the chocolate out (you may need to run the base if the tray under warm water to soften the chocolate a little). That is a bit like how plastic objects can be made. Heat, colouring and other ingredient are added to Naphtha and then the plastic is poured into the moulds to give the plastic shape.
Plastic Packets
Have a look at the plastic food packaging in your kitchen. The plastic items should have a triangle on the bottom with a number in it. The number tells you what process companies use to recycle the item. If thereís no number it probably means that the item canít be recycled.

Make Casein Plastic
Casein is a plastic that is made from milk. It was one of the first plastics ever made and was used for making things like buttons.

What you need:
An adult to help you
2/3 of a cup of milk
8 teaspoons of vinegar
a pot
a plate
a stirring spoon

What you do:
Pour the milk into the pot and get an adult to help you bring it gently to the boil. When the milk begins to steam and bubble, dribble in the vinegar, stirring the milk all the time. You will see lumps begin to form.
When the little lumps clump together to make a big solid lump get the adult to pour off the liquid and then tip your casein plastic lump onto a plate.
When it cools a little bit mould it into a shape, like a button then leave it to harden over night.
Youíll end up with hard casein plastic. The first plastic that was ever invented - itís a bit different from the plastic weíre used to!

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