My youngest daughter is doing a school experiment to demonstrate the properties of Goop/gloup/oobleck. Oobleck is a non-Newtonian fluid. That is, it acts like a liquid when being poured, but like a solid when a force is acting on it. You can grab it and then it will ooze out of your hands. Make enough Oobleck and you can even walk on it! In my Internet research here is a great film showing a fun aspect of what can be done with this substance.
Oobleck is a fictional form of green precipitation invented by children's author Dr. Seuss in the book Bartholomew and the Oobleck. In the story, a king bored with ordinary rain, sunshine, fog, and snow causes green precipitation called Oobleck to fall from the sky. The Oobleck proves to be so sticky that it gums up the whole kingdom, until the day it is saved by Bartholomew Cubbins. The word has since been used to describe a mixture of corn starch and water used to demonstrate the dilatant property of non-Newtonian fluids. Oobleck is also known in the United Kingdom as "goop" or "gloop" in many primary and nursery schools.
The recipe is as follows:
1 cup water
2 cups corn starch
a few drops of food coloring of your choice
The cornflour goop consists of small starch particles that are packed close together, between these particles there is a thin layer of water. This allows the particles to slide across each other as long as they are moving slowly. If you try to smash your fist in it quickly the starch moves faster than the water and the particles come into contact. This makes them feel solid to the touch as the force prevents them from sliding across each other. The harder the force the more solid it becomes.