Gizmos Convection Cells - Answer Key Student Exploration: Convection Cells Vocabulary: convection, convection cell, density, global conveyor belt, mantle, mid-ocean ridge, subduction zone, vector, viscosity Prior Knowledge Questions (Do these BEFORE using the Gizmo.) You place a pot of soup on the ...
Vocabulary: convection, convection cell, density, global conveyor belt, mantle, mid-ocean
ridge, subduction zone, vector, viscosity
Your text here 1
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
[Note: The purpose of these questions is to activate prior knowledge and get students thinking.
Students are not expected to know the answers to the Prior Knowledge Questions.]
You place a pot of soup on the stove. As the soup warms you notice some areas where soup is
rising up and other areas where soup is sinking down.
1. Why do you think some of the soup is rising up?
Answers will vary. [The heated soup at the bottom of pot
rises because it is less dense than the surrounding
soup.]
2. Why do you think some of the soup is sinking down?
Answers will vary. [When the soup reaches the surface it
cools, becomes denser, and sinks.]
Gizmo Warm-up
When fluids (gases or liquids) are heated, they tend to move.
This motion is called convection. In the Convection Cells
Gizmo, you will observe and experiment with convection both
in a laboratory setting and in several real-world examples.
To begin, note the laboratory setup on the MODEL tab. A
beaker of liquid is placed above a gas burner. Click Play ( ).
The burner is now heating the fluid.
1. What do you notice?
The liquid seems to swirl around in a circle.
2. Drag the eyedropper into the beaker just above the burner and let go to release a drop of
orange liquid into the beaker. What do you notice about the path of the drop?
The drop goes up above the burner, rises to the top, goes to the right, sinks down, and then
moves back to the left to start the circulation again.
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Activity A: Get the Gizmo ready:
Convection Click Reset ( ), and set Burner A to High.
Question: What causes convection cells to form?
1. Hypothesize: Click Play, add a drop, and watch the motion of the liquid. Why do you think
convection tends to occur in heated fluids?
Hypotheses will vary.
2. Observe: Click Clear drop. Under Show, select Temperature. The temperature scale runs
from red (hot) to dark blue (colder).
A. Where is the hottest liquid located? Just above the burner.
B. Where is the coldest liquid located? At the top right corner.
C. Add a drop. Does the hottest liquid tend to rise or sink? It tends to rise.
D. Does the coldest liquid tend to rise or sink? It tends to sink.
3. Observe: Click Clear drop, and then add a new drop to the liquid. Turn on Show micro
view of drop. This view shows 21 molecules in the drop. Pay attention to how fast the
molecules move and how much space they occupy as the drop moves around the beaker.
(Note: If the drop gets stuck, add a new drop to the beaker.)
A. In which part of the beaker do the liquid molecules move fastest? Above the burner.
B. In which part are the liquid molecules most spread out? At the top right of the beaker.
4. Explore: Click Clear drop and drag the probe ( ) into the beaker. Density is defined as the
mass per unit volume. It is a measure of how tightly the particles of a substance are packed.
Move the probe to different parts of the beaker, observing the temperature and density.
A. What relationship do you observe between the temperature and density?
The hotter the liquid, the less dense it is.
B. Why do you think this is so?
Sample answer: As a fluid heats up, the molecules in the fluid move faster and
collide more violently, causing the molecules to spread apart and occupy more
space. This reduces the density of the fluid.
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