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Area of Science: Chemistry Meant for at least Grade K-3 (age 5-7). This experiment is edible. An adult need not be present. |
Overview:
Combined in just the right proportions, a mixture of corn starch and
water makes a slimy-yet-firm goo.
Equipment:
Corn starch, water, container, stirring rod, measuring spoon.
Safety:
Tastes bland. Kind of messy, but you can wipe up the debris with a broom.
How to do the experiment:
Combine a handful of corn starch with a spoonful of water. Stir, and
add more water if the substance seems too crumbly. Properly mixed,
the substance should seem liquidy on top. Poke it with your finger
to make sure. Now pour a little into your hand, squeeze, and release.
Have fun, but if the ooblech seems to be drying out, add a little more
water.
Explanation:
The forces of attraction between the starch molecules and the water
vary with the amount of applied pressure. When are the attractive
forces strongest? When are they weakest?
Useful References:
Non-Newtonian
Fluids (MadSci Archives).
Or try running a search for Non-Newtonian, fluid on the MadSci Search Engine.
Further comments:
This experiment was wholly inspired and suggested by Jay Greytok at
the Haverford School in Haverford, PA, USA.