Wednesday, 10 October 2012

Jelly on a plate

Long time readers may remember that I used to perform many and various experiments with my children. That's working with them to investigate scientific questions. Not using them in experiments. That would be wrong.

Time passed and I started to volunteer as a classroom helper for all the science classes at school, and for a while jointly ran an after school science club where the children could explore the fun parts of science that were outside the national curriculum. We set fire to things. We built rockets. We looked at the planets. We made a lot of edible experiments. And I stopped blogging about child friendly science, because there are (quite rightly) rules about writing about other people's children.

Anyway, I have missed it, and as they've got older my girls are starting to want to explore vile and strange experiments again at home, so here we have, just in time for Halloween ... exploding gummy bears!

This one couldn't be easier. Get yourself some Haribos (other scary jelly sweets are available), pop them in water, and wait for 24 hours. Make sure you keep some unsoaked ones for comparison - in many ways introducing the idea of a controlled experiment is for me the most important scientific concept my children gained from this one.

The reason they do this is down to the weird properties of gels - they behave like solids but are actually cross linked polymers (long molecules) that can hold large amounts of liquid; in practice the jelly sucks up water like a sponge. Those water releasing crystals you get for pot plants do the same thing, and anyone who has been amazed by just how full a disposable nappy can get has witnessed gel chemistry in action.

The texture of these is utterly bizarre. The children tell me they taste revolting (I think they start off revolting but that's just me) and some of the lads at school have found that if you leave them longer they begin to disintegrate. This has led them to think of more ideas for experiments - what happens if we let them dry out? Can we filter them? Would they swell faster in warmer water? How about in the fridge? What if we put them in a different liquid? Would jelly beans do the same thing?

I have other ideas up my sleeve in time for Halloween. If I can convince them to join in, I'll let you know.