How it's done
We tried this experiment with Northsound1, listen to the results:
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More fun nutrition activities at
the Rowett Research Institute, eduweb
Check out National Science & Engineering Week at:
The BA (British Association for the Advancement of Science)
Further food science ideas for the primary aged audience are presented in the ‘Food for Thought resource, downloadable at The BA
Exploring the science:
PVA (polyvinyl acetate) is a polymer or ‘long chained molecule’ - so too is starch (present in the custard powder). The borax causes cross-links to develop between the two polymers and the mixture becomes stiff. It is important to get the correct amount of borax, too much i.e. too many cross-links, and the mixture is brittle; too little and the mixture flows; just right and the mixture can be rolled into a ball and bounced! Polymers (like PVA and starch) are a very important part of our world.
Taking it further:
Custard balls that bounce just like hard rubber balls ?! Yes it’s really possible, simply follow the instructions below …
What to do:
The ingredients combine to make a fairly solid mixture which when rolled into a ball, you should be able to throw and bounce!