A Simulation of Plastic Rock

Plastic Rock is a rock that behaves like something between a liquid and a solid.  Scientists believe that the earth's mantle has this type of rock flowing through its asthenosphere. 

A simple experiment using water and corn starch will simulate the properties of Plastic Rock.  Follow these simple steps and enjoy your experiment!

1)  Put one cup of cornstarch into a shallow pan (pie plate works well).

2)  Add 2/3 cup of water.

3)  Stir until you have an evenly mixed, white liquid. (it should be hard to stir in the beginning)

4)  Add another 1/2 cup cornstarch to the mixture.

5)  As you stir the mixture, you should begin to see some interesting properties.  As you stir, the mixture should solidify, making it more difficult to mix.  However, when you stop, the mixture should liquify again.

6)  Play with this mixture!  Pick some up and squeeze it in your hand... it should harden.  Open your hand and see what happens!

7)  When you are done having fun - we played with it for about 30 minutes- clean up with hot water.

Plastic Rock is slowly liquifying from hand above to below.

8)  The excited students writing up their Laboratory Reports!

Note: if you don't see this behavior, your mixture may be incorrect.  If it remains liquidy, add more cornstarch; if it is too hard, add water a little at a time until you get the desired consistency.

Happy home schooling!

  Ellen