by Colie Haahr, CMNH Educator
Try out this easy experiment with materials you already have at home! This experiment is about surface tension, and you can make glitter magically “dance” in a bowl of water! The reaction is quick, but kids love trying it more than once. This could be a good experiment to try before transitioning to water play, which always seems to be a hit!
Shallow bowls or plates
Glitter, Pepper, Cinnamon, or All Spice
Toothpicks or Q-tips
- Set up: Pour water into bowls, and place a very small amount of all of the other liquids into lids or small bowls. A pitcher of water is helpful to reset the experiment. The experiment works best with dish soap, but using a few other substances makes it more of a true experiment, where some will work and some will not.
- Optional: have a pencil and paper handy to record observations and hypotheses
- Pour about a teaspoon of glitter into one bowl of water, and a teaspoon of whatever spices you would like to use into another. You want the glitter and spices to cover the surface of the water
- Make an observation: what happened when we poured the glitter/spices into the bowl?
- The glitter or spices stay on the surface of the water because they are hydrophobic, and they do not dissolve in water like salt or sugar would.
- Carefully dip the end of a clean toothpick or Q-tip into the liquid dish soap, and poke it right into the center of the bowl
- Make an observation: What happened to the glitter/spices? The glitter should move quickly to the edges of the bowl when the soap touches it.
- Repeat the process with the toothpaste, cooking oil, hand soap or anything else you decide to try
- Optional: write down what happens each time you try the experiment
Water molecules like to stick together, so when you pour a drop of water onto something non-porous, like waxed paper, the water beads up. Kids usually can picture this happening on a windshield when it’s rainy the rain drops stick together and roll down the windshield.
When you pour water into a bowl or plate, this creates surface tension.
During the experiment, you observed that the glitter and spices in the water bowls stayed right on top. Even though water molecules like to stick together, they do not always stick to other things, like the glitter and spices. The surface tension of the water allows these small particles to float on top! They do not dissolve, and usually, they do not get saturated and sink.
When you added different substances to the water, some caused the glitter and spices to move away to the sides of the bowl. Now experiments can be tricky, and they do not always work perfectly, but the oil should have made no changes to the water bowl, and the soap and toothpaste should have caused the particles to move. The substances that made the glitter and spices had something in common: they all clean things!
Dish soap should have worked the best, and this is partially because dish soap has molecules (teeny tiny parts) that are BOTH hydrophobic and hydrophilic. Wait, that would mean the soap molecules repel water molecules, and attract or bond to them! This is true, soap is a good cleaner because it can pull things like oil out of water because of the hydrophilic properties, like when we wash dishes, dish soap helps to get rid of grease and oil that water alone can’t remove.
When the soap touched the water bowl, it broke the surface tension of the water, and that’s why we could see the glitter and spices move. Soaps and cleaners are designed to break down the surface tension of water. This helps make them good cleaning tools. When you added the dish soap or toothpaste to the water it broke up the surface tension. The water molecules, however, want to stick together and maintain that tension, so they move away from the soap, carrying the glitter and spices with them! We can see the reaction because there are particles floating on the top of the water. The water would still move when soap is added, but because it is clear, we can’t see it. The glitter and spices help us see what’s happening in the water bowl!