Nothing happens if you drip food coloring onto milk, but once you add a drop of dishwashing liquid, the milk turns into a swirling wheel of color. Here’s how to perform the magic milk science experiment and a look at how it works.
Magic Milk Materials
This is a great science project for kids because all you need is milk, food coloring, and dishwashing liquid. It’s also easy on your pocketbook because you only need a little of the ingredients.
- Food Coloring
- Dishwashing liquid
How to Do the Magic Milk Science Experiment
- Pour enough milk to cover the bottom of a small place or shallow saucer.
- Add a few drops of food coloring. You don’t need to use different colors, but if you do, you can explore how colors combine to make new ones.
- Observe how boring this is. The food coloring drops stay where you put them and may even sink into the milk and disappear.
- Drip a droplet of dishwashing liquid onto the center of the milk. You don’t need to stir the milk. The colors immediately start to swirl on their own.
How the Magic Milk Experiment Works
Adding food coloring to milk doesn’t have much of an effect. Yes, you can color the milk if you stir it, but if you don’t stir it the color spreads by diffusion. Diffusion is a slow process and not very interesting to watch.
When you add dishwashing liquid, the colors start to swirl. Dishwashing liquid is a detergent. Detergents lower the surface tension of the water in the milk, making it easier for the ingredients on the plate to mix. You can observe surface tension if you pour water or milk into a glass and note you can overfill the container slightly. The anti-gravity water science trick also relies on surface tension.
But, that’s not all detergent does. Detergent is an emulsifier. Each detergent molecule has a hydrophobic (“water-fearing”) and hydrophilic (“water-loving”) portion. The hydrophilic portion orients toward water molecules, while the hydrophobic portion orients toward fat molecules. The end result is that detergent forms tiny spheres called micelles that separate the fat from the water. Basically, an emulsifier helps two immiscible (unmixable) liquids mix. The food coloring swirls throughout the milk as the detergent forms micelles around fat globules within it. The fat content of the milk matters. Skim milk contains very little fat, so the detergent doesn’t have a big effect on it. 2% milk and whole milk work much better for the magic milk project because they contain enough fat to cause a visible reaction between the detergent and milk.
From Project to Science Experiment
Science projects work due to scientific principles. For young explorers, you can explain that detergent changes the properties of milk so colors added to it mix better. Explain that the same process happens when you wash dishes. The detergent makes it easier for oil and grease to lift from dishes and get rinsed away. Also, this is a great project for kids to explore colors. They can see that blue and yellow combine to make green, red and blue combine to make purple, and so on.
But, older children can turn the science project into a science experiment. The difference is that an experiment uses the scientific method. In a nutshell, an investigator observes the project, makes a prediction or forms a hypothesis about what will happen if one thing is changed, and then conducts and experiment to see if the prediction was correct. Here are some ideas of factors to change to turn the magic milk project into a true magic milk science experiment.
- What happens if you increase the fat content of milk? You can compare skim, 2% milk, whole milk, and half-and-half. Or, you can mix oil in with milk before continuing the project. Is there a point where the thickness of the milk slows down the reaction?
- Does the project work with water? With vegetable oil? What happens if you mix water and oil and try the project?
- What happens if you sprinkle glitter onto the milk before adding the detergent?
- Temperature affects the rate of many processes and chemical reactions. Is there any difference if you use very color milk compared with hot milk?