Both my kids actually said “wow!” when we did this experiment, and kid M wanted to do it again and again (I had to call it a day after 3 goes as we were running out of milk!).
What you need:
- Milk (essential – any type will do).
- Food colouring (essential – any colour will do).
- Washing up liquid (essential).
- Cotton bud (essential).
- Plate (essential – to reduce spillage one that has a slight indent would be ideal).
What to do:
- Pour a layer of milk onto the plate and then add a few drops of food colouring. See what happens to the milk and food colouring.
- Dip a cotton bud in some washing up liquid and then place in the middle of the plate. Watch what happens.
- Using several colours of food colouring at once makes some lovely patterns in the milk.
- Our green food colour spread out over the surface of the milk but the blue and pink remained in nice blobs until we added the washing up liquid, so experiment with different food colourings if it isn’t giving you the right effect.
The science bit
Some substances don’t mix well together, such as the food colouring and the milk. The washing up liquid is attracted to both the milk and the food colouring, so adding this allows them to mix together.
Explaining it to children
The milk and the food colouring do not mix well. However the washing up liquid mixes with both the milk and the food colouring, so when it is added everything mixes together.
Experiment based on an activity from the fantastic Usborne Activities: 365 Science Activities book.