Simulating Plasticity (SCOS:2.02)
Problem: How can the property of plasticity be simulated?
Objective: In this activity, students will use a cornstarch-and-water mixture to simulate the plasticity
of the earth's mantle.
Materials: Each group of students will need 30 grams of cornstarch, 20 milliliters of water, 2 small
beakers, a spoon, and a pipette.
Procedure:
a. Using the pipette, gradually add one pipette-full of water to the cornstarch. Stir the mixture.
c. Continue adding water, one pipette-full at a time. Stir the mixture after each addition. When the
mixture becomes difficult to stir, do not add any more water.
d. Try to pour the mixture into your hand.
e. Try to roll the mixture into a ball.
Observations:
1. Before the addition of water, is the cornstarch a solid, liquid, or gas? Is the water a solid,
liquid, or gas?
2. When you try to pour the mixture into your hand, does the mixture behave like a solid,
liquid, or gas?
3. When you try to roll the mixture into a ball and apply pressure, does the mixture act like a
solid, liquid or gas?
Analysis
1. How is the mixture of cornstarch and water similar to the earth’s mantle?
How is it different?
2. How might plasticity of the mantle influence the movement of the Earth’s lithospheric
plates?
3. Describe how you might make a model of a lithospheric plates. Explain how you could show
how the plasticity of the mantle allows the Earth’s lithospheric plates to move.