Before beginning the activity, have students read through it in its entirety. Then, review the structure and characteristics of the mantle and crust of the earth.
Collect the following items:
- hot plate; turn it on to medium heat when ready to begin
- 250-mL or larger beaker
- food coloring
- rolled oats
- on a separate sheet of paper, have students draw outlines of two beakers; labeling one A and the other B
- Fill the beaker about 2/3 full of water. Place it on the hot plate. Be careful to keep hair, fingers, hands, and loose clothing away from the hot plate.
- Wait about two minutes, then using the dropper carefully add one drop of food coloring to the surface of the water near the side of the beaker. Do your best not to disturb the water.
- Observe the path of the food coloring for as long as possible. Draw your observations of the movement of the food coloring in the beaker you labeled A.
- Repeat steps 2 and 3 if you have difficulty observing the movement of the food coloring.
- Sprinkle one spoonful of the rolled oats evenly across the surface of the water in the same beaker. Observe the path of the rolled oats on the water.
- In the beaker you labeled B, draw your observation of the movement of the rolled oats in the beaker.
- Turn off the hot plate. It will be hot for some time. Once the beaker has cooled, remove it from the hot plate and dispose if its contents.
Describe the path taken by the food coloring. What pattern did you see in its movement? (Students may have observed the food coloring sinking to the bottom of the beaker and then swirling to the top. The may have also seen circular patterns in its movement)
What part of the earth does the water represent? (mantle)
Describe the pattern taken by the rolled oats. How does the movement of the rolled oats compare with that of the food coloring? (The oats should float on the water’s surface and follow the direction of the food coloring at the surface of the water)
What part of the earth could the rolled oats represent? Why? (The oats represent the crust, because they drift on convection currents.)
How is the water similar to the mantle? How does it differ? (The water is similar to the mantle in that it is fluid and can carry convection currents. It is different because it is muss less dense, moves more rapidly, and is cooler.)
Once the water is completely heated, it no longer serves as an accurate model of the mantle. Why? (Once the water is completely heated, it may begin to boil. If it is evenly heated, the currents will stop.)
- Write a short paragraph explaining how the beakers of water model the movement of material in the mantle.
- Convection is a process where heat transfers in substances. Convection currents are experienced every day. Give three examples of convection that you have experienced. In each example, explain what type of matter is moving in each.
- In the mantle, material is much thicker and denser than water. Try heating a thick, but flowing substance, such as oatmeal or a mixture of flour and water. Record your observations.