Name
Period
Date
CHAPTER 1 CHAPTER INVESTIGATION A
Convection Currents and Plate Movement
MATERIALS
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oven-glass lasagna pan
2 bread pans or 2 bricks
water
liquid food coloring
2 small candles
matches
2 sponges
scissors
3-4 pushpins
PURPOSE
In this investigation, you will
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observe the movement of convection currents
determine how convection currents in Earth's mantle could move tectonic plates
PROBLEM
How do convection currents in a fluid affect floating objects on the surface?
HYPOTHESIZE
Write a hypothesis to explain how convection currents affect floating objects. To write
your hypothesis, complete the sentence below:
If convection currents move in ____________________, then objects above them will
____________________, because ____________________.
PROCEDURE
Check off each step as you do it.
1. Set up the experiment.
a. Put the glass pan on top of the two
overturned bread pans or bricks
b. Fill the glass pan with water to a depth of 4
cm.
2. Observe the movement of the water when not heated.
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Hold the eyedropper over the middle of the pan and squeeze
several drops into the water. Do not touch or disturb the water with
your hands or the eyedropper.
Write down your observations.
3. Observe the movement of the water when heated.
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Light two candles and put them under the center of the pan.
Squeeze several more drops of food coloring into the middle of the
pan.
Observe what happens for a few minutes. Write down your
observations.
Blow out the candles and wait until the water stops moving before doing the next
step.
4. Make models of South America and Africa.
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Wet the two sponges.
Cut one sponge into the shape of Africa with the scissors. Cut the
other into the shape of South America. Insert the pushpins.
5. Observe the movement of your models on water that is not heated.
a. Fit the Africa and South America sponges b. Gently place the sponges on the surface
together.
of the water in the pan.
c. Observe the sponges for a few minutes.
Write down your observations.
6. Observe the movement of your models on water that is heated.
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Light the two candles again. Place them under the pan. Make sure
they are directly under the two sponge continents and in line with
the center "coastlines" of the sponges.
Hold the sponges lightly together until the water heats up. Release
the sponges and observe them for a few minutes. Write down your
observations.
OBSERVE AND ANALYZE
1. Record Draw diagrams to show how the food coloring and the sponges move in the
cold water and heated water in the boxes below. Use arrows to show the motion.
Movement in cold water
Movement in heated water
2. Analyze Did the food coloring and the sponges move more with or without the
candles? Use what you know about convection to explain how the candles changed the
way the sponges moved.
CONCLUDE
1. Evaluate Water is a fluid, but the asthenosphere is not. What properties of the
asthenosphere allow it to move like a fluid and form convection currents?
2. Compare and Contrast In what ways is your setup like the Earth's asthenosphere and
lithosphere? In what ways is your setup different?
3. Analyze Compare your results with your hypothesis. Do your observations support
your hypothesis? Why or why not?
4. Interpret Write an answer to your problem statement.
5. Identify Controls Did your experiment include controls? If so, what purpose did they
serve?
6. Explain how the continents of Africa and South America are drifting apart.
7. Apply Suppose you own an aquarium. You want to make sure your fish are warm
whether they swim near the top or near the bottom of the aquarium. The pet store sells
two types of heaters. One heater extends 5 cm below the water's surface. The other heater
rests on the bottom of the aquarium. Based on what you learned in this activity, which
heater would you choose? Why?
ANSWER KEY
Observe and Analyze
1. Diagrams will show no motion in cold water and will show objects moving apart in
heated water.
2. more with the candles; Candles heated the water at the bottom; hot water rose to the
surface where it cooled; the cool water sank, only to be heated once again. Candles keep
convection currents going.
Conclude
1. The heated rock is soft and able to move, so it can circulate slowly.
2. Similiar: heat source, layers, objects on the surface. Different: water is more fluid, the
candles are concentrated in one spot, the sponges are much smaller and don't cover the
surface area
3. Students should explain why their hypothesis was supported or not.
4. Student answers should mention the fact that convection currents move objects on the
surface.
5. Yes, the controls were the food coloring and the sponges in cold water. The controls
served to show there was no other cause of movement.
6. At the mid-ocean ridge, the new crust is pushing the old crust aside. The spreading
center moves the oceanic crust like a conveyor belt. As the crust moves, the continents
are carried farther and farther apart.
7. The heater that rests on bottom-it will create convection currents that circulate warm
water throughout the entire aquarium.
TEACHER NOTES
Lab Preparation
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Work with the class as a group to write the hypothesis for the experiment.
Have students create their own lab datasheets. They should make a fullpage, twocolumn chart with the column headings Cold Water and Hot Water and the row
headings Food Coloring and Sponges.
Create two stations, each with a set of the materials listed.
Prior to the investigation, have students read through the investigation and prepare
their data tables. Or you may wish to copy and distribute datasheets and rubrics.
UNIT RESOURCE BOOK, pp. 62-70
SCIENCE TOOLKIT, F14
Lab Management
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If possible, students should work in small groups. Each student should have the
chance to do something in the experiment—for example, light the candles, hold
the sponges, write the observations, and so on.
Tell students to line up the matching “coastlines” so they are centered lengthwise
over the candles.
SAFETY Advise students to be careful with the matches and to return them to you as
soon as they finish.