Gizmos Convection Cells - Answer Key Already Graded A+ 100% GUARANTEED A ✔

Convection Cells Answer Key

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.)

[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:

Convection

Get the Gizmo ready:

 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.

(Activity A continued on next page)