Tie-Dye Milk Experiment: Learn Chemistry in Your Kitchen

Learn about molecules and more with this tie-dye milk experiment

Make a rainbow of colors swirl around with materials you can find in your kitchen and a dash of science!

 

Atoms and molecules are the particles that makeup everything. What element or elements they are, how they’re arranged, how they move, and how they interact with each other determines how a substance looks, acts and reacts. However, atoms and molecules are very, very small. You could line up 70 million helium atoms in a row across a pencil eraser!

 

This makes them way too small to see with our own eyes or even with many microscopes. But we can observe molecules in motion with this tie-dye milk experiment.

Materials you will need:

  • Milk or cream
  • Food coloring
  • Cotton swabs or toothpicks
  • Dish soap
  • A dish or plate with a rim that can hold liquid.

Directions:

Step 1: First, add some milk or cream to your dish. You want to make sure the milk completely covers the bottom of the dish, but you don’t need to completely fill it.

A dish of milk for tie dye milk experiment

Step 2: Next, add 4 drops of food coloring to the center of the dish, being careful not to let them mix. Don’t stir the milk and food coloring! You want them to stay separate for now.

Add dye to milk

Step 3: Pick up your cotton swab or toothpick. Carefully cover one end of it with dish soap.

Add dish soap to a qtip to create tie-dye milk effect

Step 4: When you’re ready, touch the center of the milk with the soapy end of your swab and watch the colors move!

The result of tie-dye milk experiment

The Science of Tie-Dye Milk

  • Milk is a mixture. It’s mostly water, but it also has proteins, fats, and other molecules mixed in.
  • Because milk is mostly made up of water, it acts a lot like water and has many of the same properties.
  • One of these properties is called surface tension. Surface tension is how resistant a liquid is to external force, or how strong the surface of the liquid is. It’s a bit like the surface of water having a sort of “skin.” This is how some insects can walk on water.
  • Soap is what we call a surfactant. It lowers the surface tension of a liquid.
  • When we dip the soap in the milk, it lowers its surface tension and causes not just the water molecules, but fat and protein molecules, to move as they quickly rearrange themselves.
  • By adding food coloring, we can see the movement caused by lowering the surface tension.

Expand on This Activity:

  • Ask Your Scientist the Following Questions:
    • What new colors do you see?
    • How are the colors moving?
    • Why do you think this happened?
  • Keep Experimenting:
    • Press down on the bottom of the dish with the soap-covered cotton swab for three seconds, then lift up. How is the movement of the colors different than when you quickly touch the cotton swab to the milk’s surface?
    • Touch the cotton swab to areas where the colors have collected to watch the colors continue to move.
    • Try the experiment with more or fewer colors of food coloring. How is the tie-dye different?

The Science of Tie-Dye Milk

  • Milk is a mixture. It’s mostly water, but it also has proteins, fats, and other molecules mixed in.
  • Because milk is mostly made up of water, it acts a lot like water and has many of the same properties.
  • One of these properties is called surface tension. Surface tension is how resistant a liquid is to external force, or how strong the surface of the liquid is. It’s a bit like the surface of water having a sort of “skin.” This is how some insects can walk on water.
  • Soap is what we call a surfactant. It lowers the surface tension of a liquid.
  • When we dip the soap in the milk, it lowers its surface tension and causes not just the water molecules, but fat and protein molecules, to move as they quickly rearrange themselves.
  • By adding food coloring, we can see the movement caused by lowering the surface tension.

Learn More: Chemistry

  • Many atoms and molecules have positive (+) or negative (-) charges. An atom or molecule with no charge is called neutral. Positive and negatively charged atoms attract, just like the north and south poles of a magnet.
  • Molecules can be polar or nonpolar. Polar molecules have one side that is much more positive or negative than the other. Nonpolar molecules don’t have a difference in charge. Polar molecule likes to mix with other polar molecules, and nonpolar molecules like mix with other nonpolar molecules. Polar and nonpolar molecules don’t mix. This is what keeps oil and water separate; oil is made of nonpolar molecules and water is made of polar molecules!
  • Water molecules have a positive side and negative side. This makes water a polar molecule. Because of this, water molecules can stick to each other. Molecules in liquid sticking to each other is known as cohesion. The cohesion between the water molecules at the surface is what creates surface tension.
  • Soap molecules have a negative side and neutral side, so it has both a polar and nonpolar end. The negative side of the soap molecule is attracted to the positive side of the water molecule, weakening the attraction between the water molecules and lowering the surface tension.
  • But that’s not all. The neutral sides of the soap molecules also interact with the nonpolar fat molecules, separating them out of the milk. This is how soap is able to clean up greasy messes!

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