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Author(s): Nancy Moreno, PhD, Barbara Tharp, MS, and Judith Dresden, MS.

Exploring Dispersion

Complete instructions for conducting activities in this slide set, including materials needed, setup instructions, student sheets (in English and in Spanish), answer keys and extensions, can be found in The Science of Air Teacher’s Guide, which is available free-of-charge at

Part 1: Indoors

1. Arrange the pieces of string on the floor like spokes of a wheel around a central point in the room (see PDF for illustration). Divide the class into three groups. Tell the members of one group to sit on the 2-meter marks on the various pieces of yarn. Tell the second group to sit on the 4-meter marks, and the third group to sit on the 6-meter marks.

2. Stand in the center of the “wheel” holding the orange. Before you proceed, tell the students that they should raise their hands as soon as they smell the scent from the orange.

3. Begin to peel the orange, hold it in your hand and turn around slowly. Record (or have one or more students observe and record) the times when approximately three-fourths of the students at each distance have raised their hands.

4. On the board, create a graph showing the time it took for the group at each distance to smell the orange. (Leave the graph on the board until after you have conducted the outdoor portion of the activity.)

5. Use the graph to talk about odors traveling through the air. Ask questions such as, Which group smelled the orange first? Which one smelled it last? Why do you think that happened?

Part 2: Outdoors

1. Ask students, What do you think will happen if we peel the orange outside? Will you smell it more quickly or more slowly? Have students record their predictions.

2. Repeat steps 1 through 3 from Part 1 in an outdoor location.

3. After returning to the classroom, make a second graph, using the same scale as on the first, to show the time required for odors to travel outdoors. Compare the two graphs, and discuss differences. Ask, In which environment did you smell the odor more quickly? Was the odor stronger in either place? Could everyone smell the scent in both locations? Why do you think that happened? (In most cases, the scent will be noticed more quickly indoors. However, air currents indoors and breezes outdoors may affect the results. Discuss these variations with the class.)

Part 3: Compare and Contrast

In a class discussion, relate this experiment to the movement of particles through air (see the activity, “Moving Air”), and lead students to understand how pollutants can become concentrated in indoor environments. Ask, What do you think an odor is? (It can be a gas or tiny particles of liquid floating in the air. Explain that many gases and particles float in air all the time.) Ask, What happens when things floating in air get trapped inside a room? What if it were a harmful gas? How could pollutants in air enter our bodies?

Funded by the following grant(s)

National Institute of Environmental Health Sciences, NIH

National Institute of Environmental Health Sciences, NIH

My Health My World: National Dissemination
Grant Number: 5R25ES009259
The Environment as a Context for Opportunities in Schools
Grant Number: 5R25ES010698, R25ES06932

Houston Endowment Inc.

Foundations for the Future: Capitalizing on Technology to Promote Equity, Access and Quality in Elementary Science Education