Download Can a Solid Also be a Liquid?

Author: Terri Detrick
Title: Can a Solid Also be a Liquid???
Grades: 5-8
Subject Area: Earth Interior (Asthenosphere)
Description: Introducing students to the concept of the Asthenosphere as part of our
Earth’s Physical Layers. This lesson is designed to help students grasp the
concept of plasticity and how convection currents move through the
asthenosphere.
Length of the Lesson: 50 minutes
Student Objective: 1.) TLW investigate the physical properties of the Earth specific to
the Asthenosphere. 2.) TLW explain plasticity and convection currents in
the asthenosphere and how they relate to the movement of the lithosphere
plates.
Materials:
Teacher: Structure of the Lithosphere model overhead from book
Large 1000mL beaker
Water
Hot plate
Food Coloring
Silly Putty
Student: (per group of 4)
1 pie tin
1 plastic Spoon
100mL beaker with 20mL of tap water
40mL cornstarch
Procedure of Lesson:
1. Opening Question? Have you ever heard of anything being a solid and
liquid? Can it happen?
2. Teacher takes out a ball of silly putty and rolls it in a ball. What
happens to the silly putty when it sits out for a while? Place the ball of
silly putty on a front table so all can watch.
3. What are Convection currents? ( some previous information has been
covered)
4. Teacher demonstrates the movement of convection currents by boiling
water in a 1000mL beaker on a hot plate. When water is boiling drop
one or two drops of food coloring into the water. Students observe the
circular motion. Discuss density of the food coloring and the
movement through the water.
5. In order to have the convection currents we have to have some type of
liquid in the asthenosphere. Refer back to the silly putty has it changed
its shape at this time? (It should be spreading out.)
6. Explain how this is like the asthenosphere. At times it acts like a solid
and at other times like a liquid.
7. Remind students that convection does NOT occur as quickly as the
boiling water. It takes millions of years to go through the cycle. But it
is on going...
8. If the asthenosphere is both a solid and liquid how is this possible?
(Refer to the book page 117.)
9. Have students gather materials and make a model of the asthenosphere
using cornstarch and water.
10. Students pour about 30mL of tap water into the bottom of a pie tin.
11. Students now add teaspoons of cornstarch into the water a little at a
time while stirring.
12. Students stop adding the cornstarch when the consistency is such that
they can take a spoonful and raise it allowing it to flow out into the pan
like hot cheese on a pizza.
13. Have students now tap on the mixture with their finger. What do they
observe? ( It should bounce right off leaving no print)
14. Now have students take their finger and gently lay it in the mixture.
What happens? (The finger should sink to the bottom of the pie tin.)
15. Explain this is like the asthenosphere. At times it acts like a liquid and
under extreme pressure it acts like a solid.
16. Have students put some in their hands and squeeze. Then open the
hand. Discuss what occurs.
17. Clean up area. (DO NOT PUT THE CORNSTARCH MIXTURE
DOWN THE DRAIN. IT WILL CLOG!)
Scientific Explanation to Clarify Lesson:
Pressure can make matter in the asthenosphere flow without being a
liquefied. As intense heat from the Earth’s core moves toward the surface
through the mantle, it causes the material of the asthenosphere to
circulate Matter rises through certain parts of the asthenosphere. Then it
cools and slowly sinks in other places. This circulation is slow. A piece
of rock may take millions of years to rise through the asthenosphere. This
movement has a very important effect on the lithosphere.
Assessment:
Students Journal in their notebooks the following: Teacher collects and
assesses points.
1. Explain how the asthenosphere moves.
2. Describe plasticity.
3. Explain how you think this affects the lithosphere.
4. What did you learn today that you did not previously know?
Extensions:
1. Students make a physical model of the earth labeling each part and
explain how each affects the other in their relationship to heat, pressure,
and density.
2. This may lay the ground work for a unit on the continental drift theory
and plate tectonics.
3. Students come up with other ways to demonstrate the movement of the
asthenosphere/plasticity.