Science Fair Topic
The purpose of this project is to show how changes in pressure, instead of temperature, can change the properties of some materials. The substance were going to create to show this , is called Oobleck, a suspension that behaves like a liquid or a solid depending on the pressure. Applying pressure to the mixture adds to its viscosity (thickness). A quick tap on the surface of Oobleck will make it feel firm because it forces the cornstarch particles together. But dip your hand gradually into the mix, and watch what happens—your fingers slide in as smoothly as if it was water. Moving slowly provides the cornstarch particles time to move out of the way. Because of these properties, Oobleck is considered a non-Newtonian liquid because its flow properties are not described by a constant viscosity.
There is a simple explanation for the behavior of Oobleck. When not moving, the granules of starch are enclosed by water. The surface tension of the water prohibits it from completely flowing out of the spaces between the granules. The cushion of water supplies lubrication, which help the granules to move freely. But, if the movement is abrupt, the water is squeezed out from between the granules and the friction between them intensifies rather significantly.