Milk Rainbows

Want to explore some fun with colors?  Here’s a great one and I’m sure you have the 3 ingredients needed for this one at home.  Little ones will love watching the colors swirl around.  Older kids can easily set this up as investigation comparing the effect of different types of milk.

Here’s what you need to get started:

  • Milk (We used 2% because that’s what we drink at home)
  • Dish soap
  • Food coloring
  • Pie pan or small baking dish (we used disposable aluminum pie pans)
  • Q-tips or toothpicks (optional but fun for little ones)

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Add about 1/2  inch of milk to the pan/dish

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Add 1 drop each of different colors of dye near the center of the dish but not in the middle.

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Add a drop of dish soap in the center of the cluster of dye dots and watch the colors run away!

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Sometimes you can add another drop of dish soap and get the colors to spread more.  Sometimes not.

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Let the little ones use Q-tips or toothpicks to swirl and mix the colors around in pretty patterns.

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The Science behind the Activity:

Milk is made up of fat and protein molecules. Dish soap has the unique properties of attracting fat molecules and water molecules (It is both hydophyllic-water loving, and hydrophobic-water fearing). When the soap is added to the milk, it breaks up the fat and water molecules in the milk. As the fat molecules move around, they disrupt the food coloring causing the colors to move, swirl and mix.

Extension: Try this experiment comparing the behavior of different types of milk: whole, 2% and skim.  Why would the fat content affect or not affect this experiment?

Follow this link to see where I got the idea from and a much more technical explanation about the experiment: http://www.stevespanglerscience.com/lab/experiments/milk-color-explosion

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