Using a handful of household ingredients, Year 9 enjoyed a STEM lesson with Mrs Ainscough and made slime, which eventually this became firm enough to turn into bouncy balls.
The science the group learnt was about how some polymers are found as long chains, and if they can move freely over each other they behave like a liquid. By adding some baking soda and eyewash to PVA glue we start making cross links which hold the long chains together, this makes it behave more and more like a solid. Working the mixture allows more cross links to form taking us from a stretchable polymer towards a more solid but bouncy one.
A similar principle applies when making bread as each stretch and fold increases the gluten strands trapping CO2 in the bread as well as the surface tension of the loaf you are baking.
This lesson linked into understanding plastics and plastic products in Year 9.