Safety: This activity involves the use of Borax which is harmful when swallowed. Please ask an adult to help you. Borax is a form of soap and is used to clean clothes. It can be found in the laundry section of your supermarket.
You will need
2 plastic cups or similar containers
a sealable plastic bag
some paper towels
Paddle Pop stick for stirring
at least two plastic spoons
What to do
Measure 3 teaspoons of PVA glue into the glass jar.
Add 3 teaspoons of water and stir.
Add a couple of drops of the food colouring of your choice, traditionally slime is green.
Place approximately 1 cup of water into the other glass jar.
Stir in 1 heaped teaspoon of Borax powder. Once the mixture has been stirred thoroughly you have made a Borax solution.
Add 1 teaspoon of Borax solution to your jar of paste and stir. As you stir the slime should start to form. You might need to add a little more Borax solution. Be careful when you are adding the Borax solution, too much and your slime will go hard.
If your slime feels very wet and slippery (but is not still runny), remove it from the container and kneed it in your hands. In a few minutes, any extra Borax solution will evaporate or be absorbed.
Place the slime into a sealable plastic bag and it should keep for a while.
Remember: Have the paper towel close by to clean your hands with. If you get the slime onto fabric or carpet it can be removed with a little vinegar followed by warm soapy water. Make sure you wash your hands before and after playing with the slime.
The borax is acting as the connector for the PVA glue (polyvinyl acetate) molecules. Once the glue molecules join together to form even larger molecules, called polymers, you get a thickened substance very similar to slime.
When you mix glue with a bit of water, you make a substance that is known as a polymer. Polymers are very large molecules, formed by repeated patterns of chemical units strung together. The borax solution is a 'cross-linking' substance that binds the polymer chains together to make the glue solution thicker.
As the polymer chains get more 'cross-linked', it gets harder for them to move around, and your slime starts look like putty. Experiment with adding more borax solution to see if this indeed makes the slime thicker.
The trick to this experiment is knowing how much borax to add. It you add too little, your slime will be too sticky due to the excess glue. If you add too much Borax there will be too much 'cross-linking' and it won't feel like slime.
The key to a good disposable nappy is how tightly the polymers are 'cross-linked'. Disposable nappies have an amazing amount of science in them. To keep a baby dry, the nappy must be able to take up a large quantity of liquid and then, as nappy scientists describe it, "hold it under load" as the baby moves around.
The polymer must also be superabsorbent. Allowing liquid (wee) in and making sure it doesn't leak out, like a sponge that works only one way.
Inside a disposable nappy is a thin shell of tightly 'cross-linked' polymers. The shell makes it more difficult for liquid to leak out. The strategy for preventing leakage (a mess) under weight-bearing load (a baby) is the formation of a thin shell of more tightly cross-linked polymer (a good nappy). How good a nappy works depends on how tightly the polymers are cross-linked.
Add food colouring to your water and glue mixture
Make a Borax solution and add one teaspoon of the solution to your slime mixture