Looking for activities to keep your family busy while staying home? All you need to do is take a look around your kitchen. Chemistry is the branch of science that looks at substances and how they interact and change. This happens daily in your kitchen when doing simple things from boiling water to baking, washing dishes to (my daughter’s favorite) watching your cereal milk change colors!
“Dancing milk” is one of our favorite family science activities. And it uses ingredients you likely already have in the house.
- Plate or pie pan
- 1 cup 2 percent milk
- Food coloring
- Cotton swabs
- Pour enough milk to cover the bottom of the plate or pan.
- Add 3 to 5 drops of food coloring to the milk (I suggest adding multiple colors spaced apart). Do not stir.
- Take a clean cotton swab and touch the tip to the center of the liquid. What happens?
- Take another clean cotton swab and place a drop of dish soap on the end. Now touch this swab into the center of the milk. Avoid stirring. Did anything happen?
- What observations did you make? Did the liquid react the same way with both cotton swabs? Why do you think the milk reacted the way it did?
This activity has some great chemistry going on! Let’s look at what’s in our materials: Milk is mostly made of water, but it also contains vitamins, minerals, proteins and tiny droplets of fat. The food coloring you’re using is made of water and dye. Soap molecules are hydrophobic (water fearing) at one end and hydrophilic (water loving) at the other.
When soap is added to the milk, one end of the soap molecule is attracted to the fats (or really trying to get away from the water) in the milk, while the other end is attracted to the water in the milk and dye. These molecules zip around, trying to form clusters around the fat molecules. This rapidly mixing fat and soap causes swirling and churning, making your milk “dance!” When the fat droplets have been surrounded and dispersed throughout the milk, the motion stops.
Try touching the milk a second time with a soapy cotton swab. Did anything happen? Test your results further by swapping your 2 percent milk with skim or whole milk to see if anything changes. Find more great science activities online with CONNECT @ Arizona Science Center at azscience.org
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