Scientists in The City

The City

Stuff in The Air

Main Concepts

Many things are carried around in the city's air. Solid particles suspended in the air are a form of air pollution.
Animals (humans included) and plants cause changes in the surrounding earth, oceans and atmosphere.
Scientists form explanations from observations, previous experiences and conversations with others who are investigating the same question. When scientists have different explanations for the same observations, making more observations may help resolve the differences.
Choices have consequences, some more serious than others.

Materials

For particle collectors: stiff paper or cardboard, plastic wrap, Vaseline/petroleum jelly, scissors and tape.

The Activity

Take a "City Walk" and look for evidence of stuff in the air.

Do you see anything? (Clouds, fog, smog, windblown dirt, leaves, trash, bus exhaust, drips from air conditioners, etc.)

Do you smell anything? (Car exhaust, garbage truck, nearby bakery, restaurant, "burning rubber," someone's perfume, etc.)

Do you feel anything? (Windblown grit, mist, humidity, particles of pollen that make you want to sneeze, etc.)

Have groups of students construct a number of particle collectors. For each:

Cut a "pane" out of two thicknesses of construction paper or cardboard (any size).
Tape plastic wrap as flat as possible over one of the window holes, securing all edges.
Overlay the other part of the frame for strength and support, then tape the edges closed.
Spread a THIN layer of Vaseline over the plastic wrap window. The idea is to see the dirt, not the Vaseline layer.

As part of the experiment design, have groups decide how to identify and keep track of their collectors.

Have groups decide how and when to place and pick up their particle collectors in order to do a fair and representative study. Some ideas might include:

Number seven similar collectors, 1 - 7, and hang inside and outside the classroom window. Take down one of each, in numerical order, at the same time every day.
Prepare a number of collectors and leave them in significant outdoor spots for the same period of time.
"Wear" a collector all day as you carry out everyday activities.
Place collectors in different locations inside the school building.

Based on your walk and other observations, try to predict the type of things you might find stuck on your collector in the spots you leave them.

Discussion and Further Exploration: Have groups examine their collectors closely and record their observations. Try to compare amounts. Note particle shapes and colors. Can they identify any? Any ideas of possible sources?; Have investigators decide how best to compare results. (overhead projector, microscopes, compare to class-designed gradescale of greys, count particles of certain sizes, etc.); Have groups display and explain their study to the rest of the groups. Compare results.; Perhaps discuss some of the things that might have effected the study. Is it okay if it rained on the collectors? What should be done about the data from the ones that disappeared? Was the time period too long/short?
Extensions: Compare results to those found in a study and around home, or in a local park or playground.; Find some evidence of air pollution effecting other things. (trees dying, dirty buildings, grit on streets, statues and fancy old building details dissolving away, dark smog on the horizon, a brilliant sunset, a lighted "halo" over the city at night, etc.) Which ones are beneficial? Which ones are detrimental?; Look at different kinds of pollen under a microscope.; Seek more information on asthma and the smog index on the evening news.; Collect rain water and let it evaporate to see what/how much particulate matter is left.; Investigate the incomplete combustion (evidence: smoke and soot) of wax at a candle flame.; Stand on a sidewalk at a busy intersection and count the number of vehicles that pass in a three-minute period. Count how many of those vehicles gave off visible exhaust pollution. Record your numbers. Work out the proportion of visibly polluting vehicles to those that are not. Compare your results to those of other street corners. Plot them on a map. Do you see any patterns? Find out about local emission laws. Write to a governmental representative about your insights.