We live in the layer of the atmosphere called the troposphere. This layer contains a mixture of gases which include nitrogen, oxygen, carbon dioxide and water vapor.
When other substances enter the atmosphere, they cause a change in its composition. Sometimes these changes can be harmful and have a long term effect. These substances are called pollutants. Since most pollutants in the atmosphere are the result of human activity, we must find ways to curb these activities without affecting our quality of life.
An activity that you might use to show the various particles in the air can be found in a number of textbook activities. As the materials you will use must be left out for several days, you should look at a long range forecast and choose a time when no precipitation is expected to perform this activity.
You perform this activity by taping graph paper underneath petri dishes. You then coat the inside of the petri dish with white petroleum jelly and place the lids on each dish.
Decide on several locations where you would like to place each dish to investigate different particles. Some places of interest might be near the railroad station, the airport, the Q-bridge, and even have some teachers who live in different communities take one home for you. But you must make sure they will be placed in an area that will not be disturbed once you have them in place.
After you have placed the petri dishes in position, remove the lids and allow to remain for three days undisturbed. After the three day period, label the location on the lid, cover and return to school for observation.
Decide on how you will record your data and what benefits, if any, can be gained from the collection of these data.
Another activity that you may want to perform is found in HANDS-ON SCIENCE by Dorothea Allen. This activity allows the student to see how burning puts pollutants into the atmosphere and how they travel, once in the atmosphere by using a covered 10 gallon glass aquarium tank and burning wood chips.
The greenhouse effect is important to life on earth as it prevents the earth from becoming a frozen planet. When the sunlight strikes the earth, radiant energy is transformed into heat energy. The carbon dioxide in the atmosphere then absorbs this heat energy and does not allow it to escape back into space. This results in the earth staying warmer than if it did not have carbon dioxide.
An increase in the population and more industrialization has caused an increase in the carbon dioxide level. Some scientists and environmentalist fear that if this trend continues the amount of carbon dioxide in the air will increase so much that heat will not be able to escape and the earth will warm up more than it should, causing many disasters.
A way to show the greenhouse effect is to take a glass container with a lid and place a thermometer inside. Next to the jar have another thermometer exposed to the air. Record their temperatures and then place both in the sunlight and observe the temperature changes. You may also use one glass container and use the same procedure twice. The first time you measure the temperature of the container uncovered. You remove the container from the light and allow the temperature to return to the original temperature and repeat the procedure but this time you will cover the container.
Another problem pollutant in our atmosphere is sulfur dioxide. This product is introduced into our atmosphere mainly by the burning of coal. As sulfur dioxide dissolves in rainwater very easily, it forms an acid and is called acid rain.
Acid rain is harmful to living and non-living things. It damages buildings by causing them to corrode and high level of acids in water cause living things to die and disrupt the food chain. We will work with and understand acids better when using the Chemical Survey & Solution and Pollution Module.
The ozone layer is getting plenty of attention these days. Ozone is a form of oxygen gas and is important because it absorbs harmful ultraviolet radiation from the sun. This radiation is not only harmful to humans but can weaken the immune systems of animals.
Refrigerators, air conditioners, and aerosol spray cans are man’s contribution to the destruction of the ozone layer. The chlorofluorocarbons released into the atmosphere eventually combine with the ozone to form an oxygen molecule and a molecule of chlorine monoxide. The chlorine monoxide then reacts with a free oxygen atom setting the chlorine atom free to attack another ozone molecule. It has been estimated that each chlorine atom that is released in these reactions can change as many as 10,000 molecules of ozone to oxygen. At this rate, you can see that eventually there will not be enough ozone to effectively block the ultraviolet radiation.
To give the student a better understanding of the ozone layer and the effects of CFC’s, an activity in HANDS-ON SCIENCE by Dorothea Allen might be useful. The activity is entitled PROBING WAYS TO PROTECT THE OZONE LAYER. They research information on the ozone layer then analyze and discuss their findings.
Before we have the students start giving suggestions on how to reduce air pollution, we should have them read articles on air pollution from newspapers, magazines and textbooks. One source for articles is from the series “Science, Technology, & Society.” The text “Resources” has several articles with activities taken from newspapers and magazines on this subject.
We can evaluate the effectiveness of this section by listening to the discussions the students have and the suggestions they make to improve our air quality.