Kid Science: Fun with Milk

I have to be honest, I might have more fun with this one than the kids.  It is super simple, but pretty cool.

The supplies you need are:

1.  A plate with some milk poured in
2.  A Q-tip
3.  Food coloring
4.  Dish detergent (Dawn)

The next step is to add just one drop of each color (four colors is best) to the center of the plate of milk.

Add some Dawn (or equivalent) to the end of a Q-tip.  Take the Q-tip and place the soap end right in the center of the of the drop of food coloring. Then just watch the show.  You can move the Q-tip to different parts of the milk and add more soap to continue to show.

So what is going on?  Milk is is mostly water, but it is also contains protein and fat.   The soap molecule has two ends, one is hydrophilic and the other is hydrophobic.  The hydrophobic end does not like water, but it does like the fat.  It will bind to fat, which is why soap is used to clean dirty dishes.  As parts of the soap try to bind to the fat in the milk the binding causes all kinds of disruptions in the milk and the food coloring gets bumped all around.  This bumping causes the display you see.