At some point you may have heard someone speak of “polymers”. A polymer is a large molecule that is made of repeating structural units. These units are connected by what is called a covalent chemical bond. A well known polymer is “plastic”. In this experiment, we will make a polymer and then add a substance that will cause the polymer chains to cross link. Cross links are bonds that link one polymer chain to another. When the polymer chains are more “bound together”, they become harder to move around and begin to gel.

1. In a bowl, mix an equal quantity of Elmer’s glue and water.
2. Fill a jar with a cup with water and mix in a tablespoon of borax. Borax is a form of soap. We will continue mixing in borax until the solution is saturated.
3. Put the lid on the jar and shake well keeping an eye on how well the borax powder dissolves.
4. If the borax powder dissolves, add more borax. When you get to a point where no more borax will dissolve, then the solution is “saturated”.
5. Add about two tablespoons of the borax solution to the bowl of Elmer’s glue and water mixture. Stir quickly.
6. If you’d like, add brown food coloring if you’re trying to make silly putty or green food dye if you’re trying to make slime.

You may have to experiment a few times to determine how much borax solution to add. If you don’t add enough borax the slime will contain too much glue, which is the polymer part, and will be too sticky. Simply add more borax. Too much borax and you’ll have too much “cross linking” and the stuff will be too wet. Take it out and kneed it with your hands – the extra borax solution will evaporate.

The Elmer’s glue and water mixture, the polymer, is known as polyvinyl acetate. The borax solution, the cross linking agent, is known as sodium tetraborate. Again, experiment with the amount of borax solution to see what is needed to make the slime thicker (aka silly putty) or thinner (aka slime).

Note: another name for this substance is Gak which is actually sold as a trade name polymer known as poly-vinyl alcohol.

Suggested uses for your new substances? Take a dab of green slime and wipe under your nose. Then tell Mom you’re not feeling well. For the brown silly putty, place a lump on Dad’s chair right before he sits down. When he stands up make a scrunched up face and say “ewwww, yucky”.

 

Supplies: Food dye, Glass jar, Glue, Borax

 

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