Here is a recent science project we did at CSN; a fun experiment that makes a goopy, fun mess! Keep in mind that this is not just about fun, there is some pretty amazing science going on here!
You will need:
- Cornstarch (a 16 oz. box is good for every 2-3 participants – but more is always better)
- Food coloring (we always say it’s optional, but it does make it more fun – don’t use too much or you could end up with colored hands…and clothes…and curtains)
- A large bowl
What do you do?
- Pour the cornstarch into the bowl. Don’t rush to add water – take time to feel the cornstarch.
- After you’ve taken-in the feel of the powder, it is time to add water. You should add the food coloring to your water before adding it to the powder. (Approx ½ cup of water per cup of cornstarch).
- Mix in the water slowly and get stuck in with your hands. Part of the fun is getting gooey.
The best test is to reach in and grab a handful of the mixture and see if you can roll it into a ball between your hands – if you stop rolling it and it “melts” between your fingers – success!
- Clean up is easy but do not put it down the drain!
Cornstarch goo (sometimes referred to as “oobleck” from the Dr. Suess book) is what scientists call a “Non-Newtonian” liquid. Basically, Sir Issac Newton stated individual liquids flow at consistent, predictable rates. As you likely discovered, cornstarch goo does NOT follow those rules – it can act almost like a solid, and them flow like a liquid. Technically speaking, the goo is a SUSPENSION, meaning that the grains of starch are not dissolved, they are just suspended and spread out in the water. If you let the goo sit for an while, the cornstarch would settle to the bottom of the bowl.
So why does this concoction act the way it does? Most of it has to do with pressure. The size, shape, and makeup of the cornstarch grains causes the cornstarch to “lock-up” and hold its shape when pressure is applied to it. People have filled small pools with oobleck and they are able to walk across the surface of it (as long as they move quickly.) As soon as they stop walking, they begin to sink.