Color Changing Milk
It's an explosion of color! Some very unusual things happen when you mix a little milk, food coloring, and a drop of liquid soap. Use this experiment to amaze your friends and uncover the scientific secrets of soap.
- Milk (whole or 2%)
- Dinner plate
- Food coloring (red, yellow, green, blue)
- Dish-washing soap (Dawn brand works well)
- Cotton swabs
- Pour enough milk in the dinner plate to completely cover the bottom to the depth of about 1/4 inch. Allow the milk to settle.
- Add one drop of each of the four colors of food coloring - red, yellow, blue, and green - to the milk. Keep the drops close together in the center of the plate of milk.
- Find a clean cotton swab for the next part of the experiment. Predict what will happen when you touch the tip of the cotton swab to the center of the milk. It's important not to stir the mix. Just touch it with the tip of the cotton swab. Go ahead and try it. Did anything happen?
- Now place a drop of liquid dish soap on the other end of the cotton swab. Place the soapy end of the cotton swab back in the middle of the milk and hold it there for 10 to 15 seconds. Look at that burst of color! It's like the 4th of July in a bowl of milk!
- Add another drop of soap to the tip of the cotton swab and try it again. Experiment with placing the cotton swab at different places in the milk. Notice that the colors in the milk continue to move even when the cotton swab is removed. What makes the food coloring in the milk move?
How Does It Work?
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.
Science Fair Connection:
The Color Changing Milk activity is a great demonstration of what happens when you combine dish soap and milk. But it's just that... a demonstration. How can you make this colorful and engaging activity a good science fair project? Change something, create a new experiment, and compare the results.
- Repeat the experiment using water in place of milk. Will you get the same eruption of color? Why or why not?
- What kind of milk produces the best swirling of color: skim, 1%, 2%, whole milk, cream? Does the fat content of the milk affect the reaction?
The dish soap must remain the same in the experiment. Use the same brand for each trial and the same amount of soap. Use the same colors and the same amount of food coloring in each trial. Pour the same amount of liquid into the bottom of the dish. All of these steps ensure that you have standardized the conditions as much as possible and have isolated a variable--the one thing that changes in the experiment. In this case, the variable is the type of milk you are using. Take photos of the reactions (maybe even videotape the reactions) to document your discoveries and share at the science fair.
- Colorful explosion Review by Leticia
I am a 4th grade teacher and the reaction from my kids was amazing! Great class project to show chemical reaction.
(Posted on May 29, 2010)
- Milk Fireworks Review by Liz
This is right up there with corn starch and water for coolest simple science demonstration. Love it, can't wait to use it with students!
(Posted on January 16, 2013)
- The best science experiment ever! Review by gwen w.
It was so cool when all the colors shot out in different directions. It even works with almond milk.
(Posted on March 18, 2013)
- AWESOME! Review by Heather
This was a great science fair project for my 1st grader! Very easy and fun to do!
(Posted on May 5, 2010)
- best ever Review by Louie L.
we tried this at school for our inquiry and it was great we all went ooohhhhh and aaahhhhh. after that was over i went home and did this for about an hour and it wished i did it for longer
(Posted on May 26, 2012)
- .........WOW Review by alexa
It is soo much fun!
(Posted on August 29, 2012)
- Awesome! Review by Hannah
That is so cool! I found out that the soap is attracted to fat! Never knew that until today! ;-)
(Posted on May 9, 2012)
- M6 Quinns Beach Primary School Review by Martene M.
Dear Mr Spangler,
We loved this experiment it was great fun for the class. Except we didn't do it quite right.We Put the food colouring in the corners and didn't use a cotten swab. We love your experiments and think they are very interesting.
(Posted on March 12, 2013)
- it's so cool!!!!!!! Review by Mikee
it's awesome!i tried it one time and it worked.i told my teacher that I'm gonna do this as my science project and I told her that is is about surface tension..she told me that i can use water or water w/salt in my experiment, so it doesn't look like it's just a demonstration. Will it worked with water or water w/ salt?
again, it's so awesome and i liked it.
(Posted on December 6, 2010)
- Color Changing Milk is Kool Review by Anna Matlock
That is so kool. My name is Anna and i am doing this project for the Science Show Case at my school, Neosho Middle School, i am in 6th grade and i want to send a shout out to Mrs. Robison the best science teacher ever!!!
(Posted on May 1, 2012)