Make Silly Putty
What you'll need:
2 containers (1 smaller than the other, preferably a film canister)
Borax solution (ratio of about 1 Tbsp of borax to a cup of water)
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!