Watch milk turn into a rainbow of crazy colors with this neat experiment!
For a full step-by-step explanation with tips to get the best results, please check out my video:
Topics: Surface Tension, Chemical Reactions
Age Group: 6-10 years old
Difficulty: Easy to perform and see results
Milk (Whole or 2%)
Shallow dish or bowl
1. Pour a bit of milk into the shallow dish. Make sure there is enough milk to cover the bottom of it.
2. Put a few drops of food coloring into the middle of the milk. The more colors, the better! Here, blue, green, pink, and purple are being used.
3. Take the toothpick and put a drop of dish soap on it. Then dip this toothpick into the milk.
4. Watch the milk dance into a rainbow!
How it Works:
Properties of Milk: Many liquids, like milk, have a property known as surface tension. Surface tension is a force that causes the layer at the top of a liquid to behave like an elastic sheet, almost creating a film. This property is caused by particles in the milk getting attracted to each other and pulling themselves together, forming this "film".
Milk is composed of water, fat, protein, lactose (a type of carbohydrate-rich in energy and made of carbon, hydrogen, and oxygen). In the milk, the fats and proteins are sensitive to change.
Chemical Reaction: When the dish soap is added, the surface tension “film” is broken, allowing the soap to react with the milk’s proteins and fats. When this happens, the fat and proteins separate from the water, creating the milk’s dancing rainbow.