This is mixing oil and water-a very easy activity to do at home. I used the kitchen because it was rainy but this could be done outside to reduce risk of mess. Having said that, it should be, and was, a relatively clean activity.
We mixed red and yellow food colouring to some water. This made a rather mucky orange colour. Why orange? Probably because the yellow colouring was new and checking that red and yellow make orange seemed like a good idea.
Next, we added oil. The food colouring really makes the difference striking.
More additions, this time washing up liquid.
The whole jar had a good stir and then the effect of the washing up liquid was so obvious. Isn't it disgusting?
At the risk of teaching my Grandmother to suck eggs, what happens is that water and oil don't mix. The washing up liquid is a surfactant-its molecules have both an oil loving end and a water loving end so allow the two liquids to mix. This is how the washing up liquid clears grease from plates.
I have just added a science label to posts about anything vaguely to do with science.