Swirling Colors Milk (science experiment)

Who would have thought you could do such a colorful science experiment with milk?  We had fun at our Super Science Party adding a "secret substance" that would turn a tray full of milk and food coloring into a swirling symphony of colors!

Here's what you need:

• milk (whole or half and half ~ skim won't work)
• tray or shallow bowl
• food coloring
• cotton swabs
• liquid dish soap (Dawn works well)

Here's what to do:

1. Pour some milk into your tray.  You'll want it at least 1/4" deep.
2. Add several drops of food coloring near the center of the tray.
3. Dip a cotton swab into the color (don't stir it, just dip!).  Nothing really happens.
4. Now, dip your cotton swab into your liquid dish soap and then dip back into your milk.  (again, don't stir, just dip it in and hold it in place for a few seconds!).  Watch how the colors "jump" away from the soap, and then begin swirling around on their own!

 Look at all the fun we had at the party.

Here's the science behind the swirling colors.  (From Steve Spangler Science)

"Milk is mostly water but it also contains vitamins, minerals, proteins, and tiny droplets of fat suspended in solution. Fats and proteins are sensitive to changes in the surrounding solution (the milk).

The secret of the bursting colors is the chemistry of that tiny drop of soap. Dish soap, because of its bipolar characteristics (nonpolar on one end and polar on the other), weakens the chemical bonds that hold the proteins and fats in solution. The soap's polar, or hydrophilic (water-loving), end dissolves in water, and its hydrophobic (water-fearing) end attaches to a fat globule in the milk. This is when the fun begins.

The molecules of fat bend, roll, twist, and contort in all directions as the soap molecules race around to join up with the fat molecules. During all of this fat molecule gymnastics, the food coloring molecules are bumped and shoved everywhere, providing an easy way to observe all the invisible activity. As the soap becomes evenly mixed with the milk, the action slows down and eventually stops.

Try adding another drop of soap to see if there's any more movement. If so, you discovered there are still more fat molecules that haven't found a partner at the big color dance. Add another drop of soap to start the process again."

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