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When you mix corn starch and water together, how come the mixture feels like a solid at first but once you pick it up, it melts to a liquid? I did this activity when I was a kid and always wanted to know what made this happen. If you can write back that would be great. Thanks,
Question Date: 2009-04-05
Answer 1:

The mixture of cornstarch and water, often called Oobleck, is such a fun experiment! It's also a demonstration of a non-Newtonian fluid.

The cornstarch and water mixture forms a suspension: a mixture of two substances, where one is divided and dispersed in the other. In the case of Oobleck, it's the solid cornstarch dispersed in liquid water.When you quickly strike the Oobleck, you are forcing the long starch molecules of cornstarch closer together. The impact of this force traps the water between the starch chains to form a semi-rigid structure. When the pressure is released, the cornstarch flows again.

All fluids have a property known as viscosity - the measurable thickness or resistance to flow in a fluid. Honey and ketchup are liquids that have a high resistance to flow. Water has a low viscosity. Newton said that viscosity is a function of temperature.So, if you heat honey, the viscosity is less than that of cold honey. Non-Newtonian fluids, like Oobleck, have a viscosity that changes when pressure or stress is applied.

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