Milk. A beverage that most of us drink every single day, but probably not one that we give much thought to. That’s one of the reasons why huge advertisement campaigns – like the “got milk” posters and commercials – aim to reach children and adults of all ages with information about an often overlooked yet important source of vitamins and minerals in our daily diets.
We learned some interesting things about milk in our program:
- The habit of drinking milk actually became popular over 10,000 years ago when animals were first domesticated in Afghanastan and Iran. Domestic cows – where we get most of our milk – didn’t even arrive in North American until the 1600’s!
- Cows produce 90% of the world’s milk needs, and an average cow can produce the equivalent of about 90 glasses of milk a day (or 200,000 glasses during its lifetime).
- But Cows aren’t the only animals that produce the milk and dairy products that humans consume. You can add to that list goats, sheep, apes, yaks, water buffalos, reindeer, and horses!
- Why do our dentists say that milk is good for our teeth? Milk and dairy products actually reduce the amount of acidity in our mouths, curb plaque formation, and even reduce the risk of cavities.
As scientists, though, we want to know what exactly milk is…so we can figure out some fun ways to experiment with it. Think of milk as a solution of mostly water that also contains vitamins, minerals, proteins, and fat “droplets.” The proteins and fats actually float around freely in the solution. The gotmilk website actually has some very fun online games that show you just how difficult it is to create a substitute beverage for milk.
Our mission for the ‘got milk’ experiments was a simple one: What happens when you add food color drops to milk, and then introduce a drop of regular dish washing soap?
It’s important to use liquid food coloring, and not the gel food coloring that is popular in food stores now. The dish soap can be any kind of liquid dish soap – we used the Dawn brand of soap for our experiments. And just to make sure we were thorough as scientists, we conducted our test with a variety of milk types: whole milk, 2% milk, 1% milk, and fat free milk.
We poured just enough milk into a paper plate to completely cover the bottom of the plate. Each scientist determined which colors to add to the milk solution. Only 1 or 2 drops of food coloring per color is necessary, but some of our scientists wanted to add more in specific patterns throughout their plates of milk. Once the drops of food coloring were in place, we dipped a standard q-tip into the Dawn soap, and then slowly lowered it into the center of the plate of milk. What were the results?
The results were both instantaneous and VERY COOL. With just a single drop of dish soap, the colors instantly begin to swirl around the milk in crazy patterns. But why does this happen? Well, remember from our description of the milk solution that the fat droplets are actually floating around in the main solution of the milk. The dish soap molecules are designed to instantly want to attach themselves to fat molecules. [That’s why dish soap does such a good job of cleaning up greasy pots and pans.] As the soap molecules race around the solution trying to attach to the floating fat droplets, the food coloring molecules are frantically pushed around the plate. Hence, the crazy swirling of colors that the G3 scientists witnessed!
Well, we all agreed that the best results were seen with the whole milk, which was also the milk with the highest fat content. But there actually wasn’t a huge different between the whole milk and the other kinds of milk. Whole milk has a fat content of about 3-4% (so not a huge difference between whole milk and either 2% or 1% milk). The biggest difference noted by our G3 scientists was the rate at which the colors swirled. The reaction was faster-moving with the whole milk and got increasingly slower as we used the milks with lower fat content. We even continued to see a reaction in the supposedly no-fat milk which led our scientists to the conclusion that no-fat milk actually must have at least a trace amount of fat present in its solution.
What would happen if you tested this with other liquids/beverages? This is a simple experiment that can be done at home. Just be careful with the food coloring since it will stain just about any material. You can also read more about this experiment by reading the “Color Changing Milk” experiment on Steve Spangler’s web site. And stay tuned for what we’ll be doing in our next program! I’m thinking it will involve creativity, possibly some teamwork, and maybe even a stop watch 🙂