Magic Milk Science Experiment

This easy magic milk science investigation is fantastic fun for kids of all ages. All you need is whole milk, food colouring and a little dish soap to create crazy colour explosions. Older children can use this activity to learn about emulsions.

The reaction that gives the colourful display is between the fat molecules in the milk and dish soap. This is why whole milk is the best to use.

food colouring patterns on a layer of milk for a magic milk experiment

How to set up a magic milk investigation

You'll need

Whole milk

A shallow tray

Food colouring

Pipette

Washing up liquid ( dish soap )

Instructions

1. Pour a layer of milk into your baking tray or plate.

2. Gently drip a few drops of food colouring onto the surface of the milk - spread these out.

Milk and food colouring in a shallow tray for a magic milk science investigation. The food colouring is spread out over the surface of the milk.

3. Add drops of the washing-up liquid on top of the food dye and watch what happens.

magic milk investigation showing how food colouring moves away from itself in milk when washing up liquid is added.

Safety: Do not drink the milk after.

What do you think of our magic milk display?

Why does it work?

Think about why we use dish soap in everyday life. It's to clean our dishes and break down the fat that makes them greasy. Milk is mainly tiny droplets of animal fat dispersed in water; whole milk has a higher fat content than semi-skimmed, which is why it's the best one to use. The washing-up liquid/dish soap breaks down the fat 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. This allows the fat to mix with the water! While doing that, it scatters the food colouring molecules, giving the colourful display you see.

Properties of emulsions

Emulsions are thicker (more viscous) than oil or water and have many uses thanks to their unique properties.

Examples of emulsions in the kitchen

Salad dressings

Ice Creams

Other examples are paint and some cosmetics.

Immiscible liquids

Immiscible liquids are those that don't mix to form a solution.

Examples of Immiscible liquids

Vegetable oils do not dissolve in water. We can use this property of oil and water to make a density jar.

girl looking through a jar of water and oil where the oil and water have separated

If a mixture of oil and water is shaken and then left to stand, tiny droplets of oil float upwards, and eventually, the two liquids will separate: a layer of oil will form on the surface of the water. However, if an emulsifier is added to the oil and water, a mixture called an emulsion forms, and the oil and water do not separate.