Studying changes of state with kids is really fun and interesting because there are so many simple experiments that can demonstrate the concepts of matter changing from solids to liquids to gases. If your kids are really curious though, introduce them to “magic muck,” otherwise known as “oobleck,” an amazing non-Newtonian fluid.
- 3/4 cup cornstarch
- 1/3 cup water
Just combine them in a bowl and let it sit for a few minutes. When you pick up a handful of magic muck and squeeze, it will form into a hard ball. Now open your hand and watch the solid ball turn back into a liquid. You can experiment by adding different amounts of cornstarch and liquid to see what happens. When you’re done playing, seal it in a ziploc bag until you’re ready to play with it again.
Here is a video of some grown-ups playing with a whole lot of magic muck!
“Non-Newtonian” simply means that it acts like a liquid when being poured, but a solid when a force is acting on it (like your hand squeezing it!). Oobleck is often referred to as a non-Newtonian substance because it doesn’t really follow Newton’s Third Law of Motion: for every action there is an equal and opposite reaction. Applying this principle, you would expect oobleck to splash when you smack it with your hand (action=smack, reaction=splash). But oobleck doesn’t splash! Instead, it actually becomes a solid for a few moments.
Why does this happen? Because cornstarch particles are structured in crystalline and noncrystalline arrangements. When slowly mixed with water, most of the water is absorbed by the noncrystalline structures. When you apply pressure, you increase the temperature and pressure and force more water to be absorbed by the noncrystalline structures, and in turn the mixture becomes thicker.
There are many non-Newtonian fluids. Ketchup and quicksand are two examples. Fluids of this type are being researched for bullet resistant body armor–useful to absorb the energy of an oncoming high-speed bullet, but still flexible and soft to wear.
- Do a little research on “cymatics” to find out why oobleck on stereo speaker dances. (There are LOTS of You Tube videos demonstrating this if you don’t want to set this experiment up on your own)
- Read “Bartholomew and the Oobleck” by Dr. Seuss
- Find out what to do if you encounter quicksand!
- Experiment more by adding different amounts of cornstarch and water to see what happens.
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