This is a great, easy, and safe experiment to do with your kids that is sure to make a lot of smiles and hopefully no spilled milk! Here is all you need to know to get started doing this Color Changing Milk Experiment.
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My kids love doing this experiment and watching the reaction between milk and dish soap create a dancing swirl of colorful milk right in front of their eyes. The best thing about this experiment is how simple it is and that it only takes a few household ingredients!
Color Changing Milk Experiment
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- Pour the milk into the bowl or on the plate
- Add food coloring to the center of the milk
- Put a drop of dish soap on a cotton swab
- Hold the soapy end of the cotton swab in the center of the milk
- Watch and observe what happens to the colors in the milk
- Try some variables like placing the soapy swab at the edge of the milk, or using skim milk, 2% milk, or whole milk.
Step 1: Pour milk onto a plate or into a bowl
This is probably the easiest part of this experiment…as long as you are careful not to spill the milk! You don’t want to make anyone cry over spilled milk!
Whether you are starting out this experiment using skim milk, 2% milk, or whole milk, use the milk of your choice and carefully pour it onto your plate or bowl. You will want to cover your plate about 1/4″ of milk, which should be about 1 cup of milk.
Step 2: Add some color to the milk
This is where things start to get a little more interesting and fun! Go ahead and remove the caps from your four different colors of food coloring and add one drop of each color to the center of your milk puddle.
It is important that the individual drops of food coloring are near the center of the plate of milk, but you also need to make sure NOT to drop the different colors of food coloring on top of each other.
When you are done adding one of each drop of color to the milk plate, your should have blue, yellow, green, and red colors in the middle of your plate ready to make the magic happen! This is also an important step to guide your kids through carefully to ensure they don’t make a colorful mess.
Step 3: Put some dish soap on a cotton swab
This step may seem simple, but make sure not to do what I did the first time and tried to put a drop of dish soap onto my cotton swab while holding it over your plate of milk! I learned the hard way that this will quickly ruin your experiment by dispersing the color in the milk prematurely.
Instead, make sure to hold your cotton swab off to the side of your plate of milk while rubbing a drop of dish soap onto it. Now you are ready to kickstart the colorful chemical reaction!
Step 4: Place the soapy cotton swab in the center of the milk
Now we are finally to the moment we have all been waiting for to watch the colors in the center of the milk dance and swirl around into a magical mixture of colors!
After getting a little soap on the end of your cotton swab, go ahead and touch the center of the milk where the food coloring is located. You will want to hold it there for about 15 seconds and watch in amazement.
Step 5: Watch and see what happens to your milk
As you hold your soapy cotton swap in the milk what do you think will happen!? Will the milk and food coloring be attracted to the soap, or repelled away from it?
That’s right! The chemicals in the soap react with the milk molecules to repel the milk away and that is why we get to witness such a colorful display of reds, yellows, greens, and blues dancing around in the milk.
Step 6: Mix it up with some variables and observe the results
Because this experiment is so easy to do and only requires a few household ingredients, why not try it a few times in a few different ways!? One way to do this would be to use skim milk, 2% milk, and whole milk and pay attention to how the colors in the milk move differently.
You will most likely get the best results by using whole milk. This is thanks to the higher fat content in whole milk that creates a more dramatic reaction with the soap molecules.
You could also place the soapy end of your cotton swab on the edge of your plate of milk and see what type of reaction occurs. Do the colors still spread from the middle outward, or do they just move to one side?
Another variable in this experiment is to place a cotton swab that has no soap on it in the middle of the milk and see if the same thing happens with the colors. Most likely you will find that instead of repelling the milk molecules, the cotton swab will actually absorb and attract some of the milk and food coloring.
This is all because the soap is the ingredient that creates the reaction and pushes the milk around. This is a great example of chemistry and how chemical reactions between two solutions can create dramatic results.
Magic milk explanation:
Although the chemical reaction between the soap and the milk looks magical, the truth is that there really is no magic involved in this color changing milk experiment.
The dazzling, colorful swirl of milk is created when the soap comes into contact with the milk because of electrically charged particles called micelles. These electrically charged particles found in the soap react with the fat molecules in the milk.
As the fat molecules move around in every direction and the soap molecules race around to catch them, the food coloring gets caught in between this battle between the fat molecules and the soap and gets pushed around to create the colorful display.
Is milk hydrophobic or hydrophilic?
Hydrophobic molecules tend to repel water, while hydrophilic molecules tend to mix with water or dissolve into water.
Because milk is mostly made up of water it could be considered hydrophilic, but it also contains minerals, vitamins, proteins, and fat molecules that can act as hydrophobic molecules.
Why does dish soap react with milk?
Soap molecules are bipolar. This means that one end of the molecule is positively charged, and the other end has a negative charge. This unbalance in charges creates what is called a hydrophobic (repels water) part of the molecule and the other end is hydrophilic (mixes with water).
When these bipolar molecules of the soap come in contact with the milk, the hydrophobic portion of the soap breaks up and connects to the fat molecules in the milk, while the hydrophilic portion of the soap molecule connects to a water molecule in the milk.
Once the soap molecules are all happy and connected to the water molecules within the milk and the fat molecules, then the race is over and the food coloring in the milk will not get pushed around anymore and the colorful whirlpool of milk will come to a resting stage.