Steve Spangler’s Cornstarch Demonstration

 http://www.youtube.com/watch?v=2olwZDsDwtI

            I picked this video simply because I thought it was entertaining.  I also found it incredibly interesting, and it made me wonder why cornstarch mixed with water acts the way it does.  When doing research to find an answer, I actually found Steve Spangler’s—the man in the video with Ellen—website.  The water and cornstarch solution behaves as both a solid and a liquid.  Because it behaves this way, it is considered a non-Newtonian fluid.  Newtonian fluids do not show signs of strain so if you were to punch water, your hand would go through it whereas if you punched a wall, your hand would stop.  This is the idea of strain.  When strained, the viscosity of non-Newtonian fluids alters causing it to get thicker and act like a solid.  This is why Steve and Ellen were able to punch the cornstarch solution and not have their hands go through it.  This is also the reason the volunteer was able to run across the tank of the cornstarch water solution.
            What is the reason it acts like a solid when under pressure?  To begin with, the cornstarch particles are not dissolved in the water but suspended.  If you were to leave the mixture sitting for awhile, the particles would eventually accumulate at the bottom.  When the mixture is punched, the cornstarch molecules are forced closer together and water is trapped between the starch chains making the mixture semi-rigid causing the solution to behave like a solid.  Then, when the pressure is removed, the solution will continue to flow.  This is why a cornstarch and water solution acts the way it does!

Here is the Steve Spangler website with the recipe for making oobleck and explaining the science behind it!
http://www.stevespanglerscience.com/lab/experiments/quicksand-goo

Submitted by: Sammy Seibel