Fill the bin with very cold water (a little ice is preferable), up to a depth of 4
inches.
2. On a flat table or desk, place four of the polystyrene (or plastic) cups upside
down on top of the four squares of cardboard. These cups will support the bin
of water so that a fifth cup of hot water can slide underneath. Place the bin
on top of the four inverted cups so that the bin is steady.
3. Draw some of the red food coloring up into the pipette and then insert the
pipette into the center of the cold-water bin to deposit the dye just above the
bottom of the bin. Expel the food coloring slowly so that it stays (mostly) in a
dense, circular area.
4. Using the blue food coloring, place two more circles of dye on either side of
the red dye, about two inches to the left and to the right. Remember to expel
the dye slowly so that it stays in dense circles near the bottom of the water Fill the last polystyrene cup with very hot tap water. Carefully slide it under
the cold-water bin so that it is under the circle of red dye.
6. Observe how the dyes move within the bin as thermal energy travels through
the system. It may take a few minutes to see the changes.
Part 2: Surface Forces
7. Empty the plastic bin and refill with fresh cold water to a depth of 4 inches.
8. Repeat steps 3 and 4 to add food coloring to the bin.
9. To model tectonic plates floating atop the asthenosphere, melt some
chocolate or wax. Using a spoon, add the melted substance to the cold water
in two or three locations. You may need to place an ice cube atop each
floater to help it solidify, or to model a more massive plate.
10. Repeat steps 5 and 6, and record your observations. In which direction do
the floating pieces move?
11. Repeat steps 7–10 two times to try new locations for the floating chocolate
or wax, or to be certain that the behaviors you observe are consistent.
Analyze
1. Describe the motion of the red and blue dyes in the bin. Draw a simple,
labeled diagram to show the movement of matter and energy. Use arrows to
show how the dyes spread out, come together, or change direction. Then,
provide a brief written explanation to supplement your drawing 2. What is the role of density changes in a convection cycle? 2 points
3. Compare what happens with the red dye in the water bin with what happens
to a hot air balloon surrounded by cool air. 2 points

4. Recall that matter cannot move without energy. What is the energy source
that moves the red dye? What is the energy source that moves the blue dye