SMMART SCIENCE: MILK SWIRLS
This fun science activity intrigued my 3 year old AND my husband!
Pour 2% or whole milk onto a saucer to cover the bottom of the dish. Squeeze a drop of food coloring carefully into the milk. Now squeeze a drop of dish soap into the middle of the drop of food coloring. (It may be easier to dab a little dish soap onto the end of a cotton swab and place that into the center of the food coloring blob.) Observe how the food coloring moves and swirls when encouraged by the dish soap. Try this activity with skim milk and water. Observe how the water-based food coloring moves more freely.
The little blobs of food coloring are sitting, sort of trapped, in the denser milk surrounding them. When the soap is added, the fatty lipids in milk are surrounded by the soap and form little micelles, or spheres of fat surrounded by soap molecules. The soap breaks the surface tension of the milk and allows the food coloring to disperse and diffuse through the milk.(This is the same concept when you are washing your laundry-the soap molecules surround the dirt and the micelles are washed away.)
Schematic of a micelle
one site you can view this idea and others:
