OOBLECK

Parent Approval

2 cups of corn starch

Slowly mix in enough water to make a thick mixture (about the texture of pancake batter) about 1- 1½ cups of water

3 drops of green food coloring (if you want)

Book Recording: Click Here

Fun Facts about OOBLECK:

• Oobleck is a solid and a liquid at the same time. • Oobleck can be molded in a container and when taken out does not keep shape. • If you make a ball and throw it up in the air, it loses shape and becomes flat in the air. • If you squeeze or punch the oobleck, the starch particles will not move out of the way quickly, so the oobleck will feel solid. • When you leave Oobleck in the sun, the color evaporates; it turns hard like cement on the top and like jelly on the bottom. When heated this also happens and it is sticky. • Oobleck does not bounce. Oobleck is a type of non-Newtonian fluid called a dilatant. • If you slowly lower your hand into oobleck, it will sink, but it is difficult to quickly remove your hand (without taking all the oobleck and its container with you). • Oobleck and other pressure-dependent substances (such as Silly Putty and quicksand) are not liquids such as water or oil. They are known as non-Newtonian fluids. • This substance's funny name comes from a Dr. Seuss book called Bartholomew and the Oobleck. • Try some other tricks… o Grab a handful, squeeze it, and let it ooze out your fingers o Make a puddle and quickly drag your fingers through it. o Put it into a plastic container and shake it or quickly bump it against a table. o Jab at the Oobleck and then slowly let your finger sink in o Put it on top of a subwoofer and play some low frequencies at high volume (tough to set up, but worth it) o Have fun and be sure to wash it all off in the end.

All the Good Stuff (Science):

What caused the oobleck to act like a solid or like a liquid? Pressure. When enough pressure was applied, the oobleck acts like a solid. When little or no pressure is applied, it acts like a liquid.

Why do you think oobleck acts like this? What size are polymers in the world of atoms and molecules? Polymers are very long chains.

How might that influence the behavior of oobleck? When pressure is quickly or heavily applied the chains have less time to move and get tangled up. When little pressure is applied, the chains have time to slide past each other.

Adding the cornstarch to the water changed the reaction time of the liquid. Usually liquids move so quickly we do not notice how long it takes them to move. Oobleck has a finite reaction time. We can see how long it takes for it to react. We can make oobleck act like both a solid and a liquid. A liquid like this is called a non-Newtonian fluid because it does not follow the rules that Newton discovered most liquids follow. A non-Newtonian fluid has properties of both a solid and a liquid and reacts to stress with increased viscosity. Can you think of other non-Newtonian fluids? Quicksand is one example. How do you think you should move in quicksand?

Adding any polymer to a liquid will increase its reaction time. However, different polymers will increase the reaction time different amounts. Most of the time, we will still not be able to tell the reaction time changed because it will still be very fast. We do not know why cornstarch increases the reaction time so much. Cornstarch often appears as a special polymer. This is an area that you could research as you learn more science.

Was the creation of oobleck a physical or chemical reaction? It was a physical change. Cornstarch (amylose) and water can be considered a colloidal suspension. A colloidal suspension is a two-phase system in which the starch and water are not dissolved but simply mixed into a permanent suspension that will not settle on standing. Other examples of colloids are blood, fog, whipped cream, foams, Jell-O®, and styling gel.