I was very excited to start my first experiment for today. Today I am making one of the best goos of all time. Cornstarch and water, also known as Oobleck (that is really how it is spelled). It is (in my personal opinion) the best non-Newtonian fluid of all time! “A non-whaat?” you might say. Bear with me until the end of the experiment and all will be explained.
With a scale, I measured four ounces of cornstarch and a half-cup of water and started to mix them together.
I am trying to get the constancy of honey so I played with it. Added some cornstarch here, a bit more water there, and before I knew it I had the perfect ratio for Oobleck. Check out the pictures.
I rolled the Oobleck in a ball,
Then I let the ball sit in my hand. All of the sudden…
What is happening here? Well when I squeeze, press, or apply any kind of pressure to the Oobleck, it hardens like clay! But when I release the pressure it turns into a runny liquid. Even the pressure of gravity makes it harden up. In this picture, I let the Oobleck go but it is pushing and pulling on itself while falling, so it seems like hard honey.
When I had a bowl full of this stuff, I pressed down hard and it seemed like I was pushing on clay. But then I rested my hand on the surface and it sank down into the liquid. I had transferred the Oobleck onto a pan. I rested my hand on it and lifted it up fast and the Oobleck was holding onto me like suction cups!
I squeezed the Oobleck together and it crumbled like dirt!
I released it.
Pretty awesome goop, huh? Let’s talk about this for a moment. It is called a non-Newtonian fluid because it’s viscosity (the thickness or resistance when it flows) changes when force or pressure is applied! Another non-Newtonian fluid is ketchup. But it does the exact opposite of Oobleck. When force or pressure is applied to ketchup it liquefies and when you release the pressure it becomes more solid! Think about it, when you put ketchup on a hot dog in that beautiful wavy shape, it stays that shape until you bite into it. Also what do you do when you need to get ketchup out of the bottle? You knock the bottle around! You apply that force and the ketchup come out of the bottle.
This makes me so happy! But how does it work? Mr. Spangler explains that when you apply force to the Oobleck the long starch molecules get forced together. The impact of this force traps the water molecules between the starch chains to form a semi rigid structure. When you release the pressure, the water molecules get back in between the starch molecules and the Oobleck flows again.
Cool! Now I am going to eat lunch and start the next experiment.
