Crazy Putty

What you'll need:

2 containers (1 smaller than the other, preferably a film canister)
Water
Food colouring
PVA glue
Borax solution (ratio of about 1 Tbsp of borax to a cup of water)


Instructions:

Fill the bottom of the larger container with PVA glue.
Add a few squirts of water and stir.
Add 2 or 3 drops of food colouring and stir.
Add a squirt of borax (possibly a bit more depending on how much PVA glue you used).
Stir the mixture up and put it into the smaller container. By now the mixture should be joining together, acting like putty, crazy putty!


What's happening?

The PVA glue you use is a type of polymer called polyvinyl acetate (PVA for short), while the borax is made of a chemical called sodium borate. When you combine the two in a water solution, the borax reacts with the glue molecules, joining them together into one giant molecule. This new compound is able to absorb large amounts of water, producing a putty like substance which you can squish in your hands or even bounce.