Non-Newtonian Cornstarch Recipe
Make your own ooey, gooey goo using cornstarch and water.
Make your own ooey, gooey glop that is guaranteed to produce a room full of ooohs & ahhhs! Using only cornstarch and water, this amazing mixture behaves like a solid and a liquid at the same time. By the end of the activity, you will have your hands on, in, and all over this wonderful solid-liquid-like mess.
- One box of cornstarch (16 oz)
- Large mixing bowl
- Cookie sheet, square cake pan, or something similar
- Pitcher of water
- Gallon size zipper-lock bag
- Newspaper or a plastic drip cloth to cover the floor
- Food coloring
- Pour approximately 1/4 of the box of cornstarch into the mixing bowl and slowly add about 1/2 cup of water. Stir. Sometimes it is easier to mix the cornstarch and water with your bare hands– of course, this only adds to the fun.
- Continue adding cornstarch and water in small amounts until you get a mixture that has the consistency of honey. It may take a little work to get the consistency just right, but you will eventually end up mixing one box of cornstarch with roughly 1 to 2 cups of water. Notice that the mixture gets thicker or more viscous as you add more cornstarch.
- Pour the mixture onto the cookie sheet or cake pan. Notice its unusual consistency when you pour it into the pan. Stir it around with your finger, first slowly and then as fast as you can.
- Skim your finger across the top of the glop. What do you notice?
- Sink your entire hand into the glop and try to grab the fluid and pull it up.
- Try to roll the fluid between your palms to make a ball.
- You can even hold your hand flat over the top of the pan and slap the liquid glop as hard as you can. Most students will run for cover as you get ready to slap the liquid, fearing that it will splash everywhere. Fear not, all of the glop stays in the pan…hopefully. If your mixture inadvertently splatters everywhere, you will know to add more cornstarch.
- As your students play with the glop, ask them to speculate as to why the liquid behaves in this manner. What causes it to feel like something solid when you squeeze it, yet flow like syrup as it drips off your finger? When you are finished, pour the glop into a large zipper-lock plastic bag for later use.
How Does It Work?
How does glop act like a solid sometimes and a liquid at other times?
Actually, glop is an example of what is called a Non-Newtonian fluid – a fluid that defies Isaac Newton’s law of viscosity. All fluids have a property known as viscosity. It is the measurable thickness or resistance to flow in a fluid. Honey and ketchup are liquids that have a high resistance to flow. When I think of viscosity, I always remember the television commercial of the child who is patiently waiting for the ketchup to flow out of the bottle and onto the hamburger bun. Be thankful that the viscosity of ketchup is greater than that of water the next time you are sitting across the table from somebody who is pounding on the bottom of the ketchup bottle.
Newton stated that the viscosity of a fluid can be changed only by altering the fluid’s temperature. For example, motor oil or honey flows more easily when you warm it up and becomes very thick when it gets cold. So, a Non-Newtonian fluid has the same dependence on temperature, but its viscosity can be changed by applying pressure. When you squeeze a handful of glop, its viscosity increases so it acts like a solid for a split second. When you release pressure, the glop behaves just like a liquid.
Ironically, the cornstarch will not stay mixed with the water indefinitely. Over time, the grains of cornstarch will separate from the water and form a solid clump at the bottom of the plastic storage bag. It is for this reason that you must not pour this mixture down the drain. It will clog the pipes and stop up the drain. Pour the mixture into a zipper-lock bag and dispose of it in the garbage.