Emily's Science Lab - Milk Fireworks - Soap Science Experiment for Kids

Have you ever wondered, why is soap so good at washing your hands? Today, we will learn about all of that and more with my experiment, Milk Fireworks. Hi everyone, I'm Emily Calandrelli, MIT engineer and host of Emily's Wonder Lab, and on my channel, we learn about all things space and science. So grab your milk and your soap, and let's make some fireworks. So why is soap so good at washing your hands? Soap is filled with long, itty-bitty chains of hydrogen, carbon, and oxygen atoms. And on one end of that chain is lipophilic. That means it's attracted to fats, oils, and dirt. On the other end of the chain, it's hydrophilic. That means it's attracted to water. So if we just use water to wash our hands with this oil and dirt, it doesn't work very well. It might get some of the dirt off, but my hands are still quite oily. So now, if we use the soap, we'll see how one end of our soap chains is attracted to the dirt and oil on my hands, while the other end is attracted to water. So the soap grabs on to the dirts and the oils and the fats, and then when we pour on the water, it grabs on to the water, and all of that dirt and oil falls right off. Parents and adults, this is such a fun one for little kids. What you need for this one is whole milk. You can use other types of milk, but I think whole milk works the best. Dish soap, some Q-tips, a plate with a little bit of a lip to it, because you want it to be able to hold a little bit of milk. And finally, you need some food coloring. So the first thing you're going to do is take your whole milk and put it in your plate, and just fill it so it fills the entire plate, just like so. Perfect. And then take your food coloring, and we're just going to do maybe like four or five drops of each color right in the center of the plate. I've noticed that the food coloring that is water-based, not gel-based, works the best for this experiment because it allows it to flow through the milk easier. Now the fun part. Take your Q-tip and put a little bit of dish soap right on the top, just like this. Now take your Q-tip, and we are going to place it right in the center where all of our food coloring is. You ready? This one is so pretty. Are you ready? Three, two, one. This is incredible. It just keeps going. So what's happening here? Well, two things. One is surface tension. Soap is something called a surfactant, which means it breaks the surface tension in water. Our whole milk is about 87% water, and so that's breaking the surface tension between those water molecules. So you have a low surface tension area right in the center, and high surface tension that still exists around the perimeter of your plate. And so all of that food coloring is running to the area where there's high surface tension. It's pulling on those water molecules. It's pulling on the food coloring to go outward radially. The other thing that's happening is the power of soap. Because while 87% of our milk is water, the other parts are fats and proteins. And so remember how I told you those chains of soap, one end loves fat and one end loves water? Well, the soap is making the food coloring dance and swirl inside the milk because of the power of soap. So a little bit of surface tension, a little bit of soap makes our milk fireworks. Do we want to try that again? That one's so fun. Three, two, one. One way you can experiment within this experiment is try different types of milk because milk will have a different level of fat in it depending on what milk you use. You can use different temperatures of milk to see how that affects it, and you can use different colors and different types of food coloring. So at this point, the surface tension is already broken, and this is just the soap dancing around in our fats and water in our milk. Thanks for making milk fireworks with me today. If you like this one, be sure to check out my best-selling Stay Curious and Keep Exploring series for 99 more science experiments. I'm Emily Calandrelli. Subscribe for all things science and space. And remember, stay curious and keep exploring. I'll see you next time.