Have you wondered what exactly is the green gooey Oobleck that fell from the sky in Dr. Suess’ book Bartholomew and the Oobleck? Mix cornstarch and water and you have something representing the effect of quicksand or Oobleck. This gooey stuff changes shape from solid to liquid in a weird way.
This a quick experiment using household items with a dramatic result. It’s perfect for younger children, but older kids find it fun as well. The fainthearted can wear gloves if they don’t like the idea of Oobleck covered hands.
- Gloves (optional)
- Green coloring (optional for the alien Oobleck)
- Iodine (optional for a dramatic effect)
What Mystery Are We Solving?
Mixing cornstarch and water is a science experiment with an ‘alien’ element. Oobleck is a non-Newtonian substance. It’s hard to the touch like a solid, but if you slowly immerse your fingers into the gooey stuff, it slides in like liquid. How is this possible and what does Newton have to do with Oobleck?
There’s nothing particularly dangerous about the experiment; it’s may be messy but not dangerous. Having an adult nearby to help is always a good idea, especially to contain the Oobleck from overtaking the kitchen or wherever the experiment is done.
If you want to pour the mixture down the drain, mix with a lot of hot water to keep it fluid.
- Place newspaper on the work surface. It will help to minimize the mess to clean up afterwards.
- Pour water into the bowl.
- Add cornstarch to the water in a ratio of 1-part water to 1.5-2 parts cornstarch.
- Stir until it forms the gooey substance.
- The right consistency is when the mixture doesn’t splash anymore but looks solid.
- Add green food coloring to create the alien Oobleck.
- For a dramatic result add iodine instead food coloring to the mixture and watch how it changes from yellow to purple.
What Just Happened Here?
From a chemical perspective, the fluid water (H20) molecule is mixed with solid cornstarch (C27H48O20) creating a colloid that is a non-Newtonian substance. Herein lies the mystery of the alien reaction. A non-Newtonian substance defies the rules of viscosity.
When pressure is added like hitting it with a spoon or pressing with your finger, the substance solidifies with increased pressure. If you slide your hands into the substance at room temperature the Oobleck acts like a fluid. Ketchup is also a non-Newtonian fluid; that’s why ketchup stays stuck in the bottle when you hit the bottom of the bottle. Quicksand, however, acts like to Oobleck; it becomes more solid or viscous with greater pressure. If you’re stuck in quicksand, the slower you move, the less resistance there is and the easier you’ll get out of it.