This easy magic milk investigation is fantastic fun for kids of all ages. All you need is full fat milk, food colouring and a little dish soap to create crazy colour explosions.
The reaction that gives the colourful display is between the fat in the milk and dish soap. This is why full fat milk is the best to use.
You’ll need:
- A baking tray or plate
- Whole milk – you can experiment using milk with a lower fat content, but you should find it doesn’t work as well.
- Washing up liquid/dish soap
- Cotton Bud
- Food colouring
- Pipette – optional – use to drop the food colouring onto the milk
Method
1. Pour a layer of milk into your baking tray or plate.
2. Gently drop a few drops of food colouring onto the surface of the milk – spread these out.
3. Add drops of the washing up liquid on top of the food dye and watch what happens.
Safety: Do not drink the milk after (obvious I know but it has to be said)
What do you think of our milk display?
Why does this happen?
Think about why we use dish soap in everyday life? It’s to clean our dishes and this break down the fat that makes them greasy. Fat is found in whole milk – milk is mainly small droplets of animal fat dispersed in water. The washing up liquid/dish soap wants to break the fat down in the milk. We call it an emulsifier as it allows the water and fat to mix creating an emulsion. The emulsifier (dish soap) molecules have a water loving head and a water hating tail. The tail sticks into the fat droplet and surrounds it leaving only the water loving heads. While it is doing that it scatters the food colouring molecules giving the colourful display you see.
Extension task for magic milk
Try testing different dish soaps to see if they all have the same effect?
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We have done this with whole milk, 2%, fat free, cashew milk and non dairy creamers- they all work. The kids (6-11) like the version with q-tip dabbing soap in. They also experimented with placement of food color droplets.