Kitchen Science Lab for Kids: 52 Family Friendly Experiments from Around the House (Volume 4) (Lab for Kids, 4)

You’ll be amazed as you watch the forces of surface tension at work in this colorful experiment.

Imagine that surface of liquids is a stretched elastic skin, like the surface of a balloon full of air. The scientific name for the way the “skin” of a liquid holds together is surface tension. When the skin of the liquid is broken by detergent, food coloring and milk move and swirl around in interesting patterns on the milk’s surface.

Step 1: Add enough milk to cover the bottom of the dish. The experiment works best with a thin layer of milk.

Step 2: In the small cup or bowl, mix together three teaspoons of water and one teaspoon of liquid dish detergent or liquid hand soap. Some detergents may work better than others.

Step 3: Put several drops of different colored food coloring into the milk. Space them out in the milk so you can see what happens when you break the surface tension.

Step 4: Dip a cotton swab into the dish-soap mixture and then touch the wet swab to the milk. Don’t stir! The detergent will break the surface tension of the milk and the food coloring will swirl around as if by magic.

Step 5: You can keep re-wetting your cotton swab with soapy water and touching it to the milk. Sometimes it works to touch the swab to the bottom of the plate and hold it there for a few seconds.