It's been far too long since I showed you my geeky side, so here is a fun little experiment to try with small people. I found it here and there are lots more to try! (Apologies in advance if I explain this badly. The original site undoubtedly does a far better job)
You will need:
Some milk (semi-skimmed or whole - skimmed won't work well, if at all)
A cotton bud (or tissue wrapped round a skewer worked for us)
Washing up liquid
First have your small helper pour some milk into the plate:
Now add food colouring - we found it works best if you use quite a lot:
Dip the tissue into the milk to get it wet, remove it, then drop some washing up liquid onto the tissue and carefully put it back into the milk - DON'T SWIRL IT!
The colours fly around the plate, making gorgeous swirling patterns as the detergent molecules desperately try to stick their fat-loving heads into the milk fat globules, and mess with the surface tension, churning everything up and shifting the molecules around. The food colouring gets taken along for the ride!
We kept adding drops of detergent to the tissue and placing it at different places in the milk until it stopped shifting. We had to do this three times before the novelty wore off ...