Have you ever made Oobleck? Oobleck is what is called a non-Newtonian fluid. It acts as a liquid when poured, but when a force acts on it, it acts like a solid! And it only requires two basic ingredients you may already have in your house. Cornstarch and regular ol’ tap water. You’ll start with about one cup of water in a bowl. Start mixing in cornstarch with a spoon. Start with about one cup, until you are able to mix it with your hands. It will probably take 1.5-2 cups of cornstarch total. Now play around with it! See what happens when you grab it with your hands, and then allow it to liquify again to ooze through your fingertips. With enough Oobleck you can even “walk on water”! This may take much more cornstarch than you have on hand, but if you fill a small inflatable tub with the mixture you can experiment this way. Or try filling a smaller dish and pressing your hand into it. Play with using different amounts of pressure to see how the mixture is affected.
The Science of Silly Putty
Another non-Newtonian fluid. Silly putty is made of polymers, or long chains of molecules (provided by the glue), cross-linked by weak hydrogen bonds (provided by the Borax). It is these bonds that allow you to roll Silly Putty into a ball and stick it to itself. When Silly Putty is stretched carefully, the hydrogen bonds break apart slowly and allow the putty to hold together. However, when the putty is pulled apart rapidly, the hydrogen bonds abruptly break apart, and the putty breaks. To make your Silly Putty, you will need the following ingredients:
-8 ounces Elmer’s glue
-1 teaspoon Borax
-food coloring (optional)
First, empty all the glue into a bowl. Fill the now empty bottle with water, shake, and stir in with the glue in a bowl until smooth. Mix the Borax with ½ cup warm water, and add this to the glue mixture. Continue stirring as the mixture thickens, and add a few drops of food coloring if you like. Now you can experiment! See how high you can bounce your Silly Putty. Now, put it in the refrigerator for an hour or so. How does it bounce now? Silly Putty has viscoelastic properties, meaning that its viscosity depends on the temperature. At higher temperatures, it will behave as a highly viscous fluid. At low temperatures, it will behave more like an elastic solid, and should bounce higher. But if it gets too cold – like in the freezer – it may shatter instead!
Tornado in a Bottle
You will need two bottles, a tube to connect them, and some water. When you whirl the liquid in the top bottle, this creates a vortex that will drain to the bottom bottle. As the water flows down, air must flow up, creating a spiraling tornado. Add glitter to make it a little more fun!
The Importance of Hand Washing!
Learn about “chasing” germs away with soap. Sprinkle ground black pepper into a shallow dish filled with water. The surface tension of the water will allow the pepper flakes to float. Since pepper is “hydrophobic”, water is not attracted to it and it doesn’t dissolve. Water likes to stick with water, and since pepper is so light, it remains floating on top. Pretend these pepper flakes are germs. Stick your finger in the dish and see what happens. Not much, right? The “germs” probably even stick to your finger a bit. Now dip the tip of your finger into some liquid dish soap, and stick it in the center of the dish. Your soapy finger should “chase” those pepper flakes to the edges! Dish soap is designed to break that water surface tension, so you can see the pepper no longer floats on top. But the water molecules still want to keep the surface tension going, so they pull away from the soap, carrying the “germs” with them! A great visual on the importance of washing your hands!