Materials Included In Kit

Additional Materials Required

Prelab Preparation

Distilled or deionized water may be used for the “unpolluted rainwater sample.”

Safety Precautions

Hydrochloric acid solution is toxic by ingestion and inhalation and is severely corrosive to skin and eyes. Wear chemical splash goggles, chemical-resistant gloves and a chemical-resistant apron. Please review current Safety Data Sheets for additional safety, handling and disposal information.

Teacher Tips

• This is a Super Value Kit. There are enough materials for 5 classes of 30 students working in pairs (75 total student groups).

• Using scissors, cut the supplied plastic tubing into 2" pieces for use in Part II, Experiment B.
• Some of the tests require an outdoor environment. Read the lab all the way through ahead of time and plan class time accordingly.
• Encourage students to place their slides for Part I in variable locations. Allow students to take their slides out of the classroom to sample the total particulates in or around their homes. Compile class data and compare individual results.
• Extra slides and labels are given for additional tests for Part I.
• The main components of the matches used in Experiment A of Part II are red phosphorous and other phosphorous compounds, sulfur and potassium compounds. The fumes from the match are comparable to the fumes emitted by some types of factories.
• Extra bromthymol blue is given to perform multiple tests for Part II, Experiment B.
• You may wish to gather rainwater samples ahead of time for use in Experiment B of Part III. If the rainwater samples are going to be kept for an extended amount of time, make sure they are covered.

Further Extensions

• Have students write reports on certain pollutants and their sources and effects. Encourage students to use the Internet and local libraries to explore the wide range of air pollution available.
• Contact local manufacturing facilities and see if you could take a tour of their plant. Discuss the steps that the company takes to reduce the amount of pollution coming from their facility.
• Visit the United States Environmental Protection Agency (EPA) website at www.epa.gov for further information on air pollution.

Sample Data

Part I. Particulates in the Air

Part II. Smoke and Acidic Gases in Air

Experiment A. Smoke from Match

Experiment B. Outside Air

Part III. Acid Rain

Experiment A. Simulated Acid Rain

Experiment B. Rainwater

Answers to Questions

Part I. Particulates in the Air

1. Did your test area have low or high particle pollution? Give examples of possible sources of particle pollution in your test area. Compare your results with your classmates.

My test area has a low amount of particle pollution. Particles may have come from clothes, natural fibers, etc. from an open window or ventilation ducts.

2. Which location had the highest number of particulates?

The highest number of particulates come from a slide placed by an open field.

3. Which location had the largest particulates? the smallest?

The largest particles came from a slide placed near a grain elevator. The smallest particles came from the slides in the classroom.

4. Which location had the most variable types of particulates?

A slide that was placed on a tree branch had the most variable types of pollutants.

5. What effect does the pH of smoke have on water in the atmosphere?

The pH of smoke may alter the overall pH of atmospheric water and cause acid rain.

6. What are some possible sources of acidic gases in air?

Acidic gases in air may be present from volcanoes, sea spray, dust from dry soils, smog and the burning of fossil fuels to name a few.

7. Explain possible outcomes of high levels of acidic gases in the atmosphere.

Acidic gases in the atmosphere may lead to acid rain and smog which presents increased health hazards to humans, causes soils to become very acidic, causes harm to seeds and plants, and damages statues and buildings.

8. What effect did the simulated acid rain have on the marble chip?

The simulated acid rain caused the limestone to break down and carbon dioxide bubbles were formed.

9. What does this experiment show about the decay of buildings and statues in metropolitan areas?

Acid rain will cause the deterioration of limestone and marble buildings and statues over time.

10. According to experiment B, are the limestone and marble buildings in your area in danger of deterioration?

Answers will vary.

11. What effects does acid rain have on plant life and other organisms?

Acid rain causes direct damage to seeds and plants. It also creates increased health hazards to humans. Answers will vary.

References

Cunningham, W. P.; Woodworth, S. B. Environmental Science: A Global Concern; William C. Brown: Dubuque, IA, 1997; pp 385–390.

Introduction

How clean is the air that we breathe? How does the air look, taste, feel and smell in your local community? In this laboratory activity, several tests will be performed to determine the quality of the air in your community.

Concepts

• Air quality

• Acid rain
• Smoke pollution
• Gases
• Particulates

Background

The major components of pollution-free, dry air are nitrogen (78%), oxygen (20.95%), argon (0.934%) and carbon dioxide (0.0314%). Air also contains trace quantities of neon, ammonia, helium, methane, and krypton. If any other substances are added to the atmosphere, an imbalance occurs that leads to the degradation of the air. The air in your area is probably polluted to some extent. Air pollution is considered as the most widespread and noticeable type of pollution. Each year in the United States, 147 million metric tons of air pollution are released into the air as a result of human activity. Worldwide, nearly 2 billion tons of air pollutants are released into the atmosphere.

There are five major classes of pollutants—particulate materials, sulfur oxides, nitrogen oxides, carbon monoxide and volatile organic compounds.

Particulate materials, also known as aerosols, are defined as any group of liquid droplets or solid materials suspended in air. Particulate materials include substances, such as dust, lint, smoke, pollen and ash, as well as may other suspended materials. Particulate material is often the most visible and noticeable type of air pollution and can be harmful to many organisms. Natural sources of particulate material in the air worldwide account for more than ten times the pollution than human sources; although in many cities, more than 90% of suspended particulate matter is due to human intervention.

Sulfur oxides occur in air from both natural and human sources. Natural sources, such as volcanoes, sea spray and dust, from dry soils all account for sulfur compounds in the atmosphere. The major source of sulfur in the air caused by humans is sulfur dioxide (which comes from the combustion of coal and oil, and smelting of ores). Sulfur dioxide is a corrosive colorless gas that is a constituent of smog. It is very toxic by inhalation and poses a strong health hazard to humans. Sulfur oxides are also one of the two major classes of gases that lead to acid rain (nitrogen oxide is the other).

Nitrogen oxide is present in the atmosphere mainly from the burning of fossil fuels. Many fossil fuels contain small amounts of nitrogen-containing compounds that produce nitrogen oxides upon combustion. Nitrogen oxide combines with the water in the atmosphere to produce acid precipitation. Rain and other forms of precipitation generally do not have a pH 7. Dissolved carbon dioxide in the atmosphere generally lowers the pH of rainwater to about 5.5. In contrast, nitrogen oxide and sulfur oxides can cause the pH of rainwater to be as low as 2.5. This is called acid rain and causes damage in many ways. Acid rain may cause high amounts of stress on aquatic life in bodies of water. In fact, many lakes in the United States have become so acidic that organisms that used to flourish have disappeared. Acid rain causes soils to become very acidic and also washes away essential nutrients from the soil. The acidity of the rain can also cause direct harm to plants by damaging leaves and preventing the germination of seeds. On a more visible, though less life-threatening level, acids released into our atmosphere can severely damage statues and erode artwork and buildings.

Carbon monoxide is a colorless, odorless gas that is highly toxic to humans and other organisms. It is present in the atmosphere mainly from the incomplete combustion of fossil fuels. If an internal combustion engine does not have the proper mix of fuel and air, carbon monoxide is formed instead of carbon dioxide. Carbon monoxide actually inhibits the respiratory system in animals by competing with oxygen for the binding sites on hemoglobin. Every year, about one billion metric tons of carbon monoxide are released into the air from the exhaust vapors of cars, trucks and other vehicles.

Volatile organic compounds are organic chemicals that persist in the atmosphere as gases. Plants are considered the largest source of volatile organic compound production. In addition to natural sources of these compounds, a high number of manmade synthetic organic chemicals such as toluene, benzene, phenols and chloroform are also released into the atmosphere. The major source of volatile organic pollution is the evaporation of gasoline from gas stations when customers are refueling.

Materials

Procedure

Part I. Particulates in the Air

1. Place a label, sticky side up, on your microscope slide. This may be done by curling two of the outside edges of the label down so the label will stick to the slide.
2. Choose a location, inside or outside, to place your slide. Be sure to choose a different location than other classmates (e.g., inside a classroom by a window, in a tree, near the corner of the school building). Choose an area that is exposed to the air, elevated off the ground and, if possible, sheltered from rain. Be sure to describe where the slide was placed. Record placement in the data table.
3. Leave the slide in the same location for seven days.
4. At the end of the seven days, collect each sample.
5. Using a magnifying glass, look at the label and record observations in the data table. Measure and draw two 1-cm squares on your label. Count or estimate how many particles are in each of the squares (look for white as well as dark specs) and record these values in the data table. Average the two counts for overall particles per square centimeter. Record this value in the data table. Total particle counts between 100 to 500 per square centimeter indicate slight particle pollution. Values over 500 particles per square centimeter relate to high particle air pollution.

Part II. Smoke and Acidic Gases in Air

Experiment A. Smoke from Match

1. Fill the sampling container to the 10-mL line with distilled water. Using a Beral-type pipet, add 5 drops of bromthymol blue indicator solution.
2. Swirl the solution in the sampling container and record the original color of the solution in the data table.
3. Light a match and place it in the solution in the sampling container and immediately close the lid. Try to capture all of the smoke from the match in the sampling container.
4. Swirl solution in the sampling container so it can interact with the fumes. Record all observations and the pH of the resulting solution. (Note: At a pH of 6.0 bromthymol blue is yellow, at a pH of 7.0 it is green, and at a pH of 7.6 it is blue.)
5. Rinse the sampling container with distilled water for use in the following experiment.

Experiment B. Outside Air

1. Fill the Sampling container to the 10-mL line with distilled water. Using a Beral-type pipet, add 5 drops of bromthymol blue indicator solution.
2. Swirl the sampling container and record the color of the solution in the data table.
3. Attach a 2-inch piece of tubing to the end of a syringe as seen in Figure 1. Fill the syringe with outside air.

4. Force the air out of the syringe through the tubing and into the bromthymol blue/water solution by depressing the plunger.
5. Repeat step 3 10 times and record all observations in the data table. (Note: If the bromthymol blue/water solution does not change color, the air in your area has a fairly low amount of acidic gases. If the solution changes to a yellow color, your local air supply contains a high concentration of acidic gases.)
6. Rinse the syringe, tubing and sampling container with distilled water. The plastic jar will be used in Part III.

Part III. Acid Rain

Experiment A. Simulated Acid Rain

1. Place a small marble chip in the sampling container.
2. Using a Beral-type pipet, place 20 drops of “unpolluted rain water” on the marble chip. Record observations.
3. Using the Beral-type pipet, place 20 drops of the “simulated acid rain solution” on the same marble chip. Record your observations.
4. Rinse the sampling container with distilled or deionized water for use in Experiment B.

1. Gather a small sample of rainwater in the sampling container or another jar.
2. Dip an acid rain test strip into the water.
3. Compare the color of the test strip to the color chart. Record the color of the test strip and the acidity of the rainwater in your area in the data table.

Student Worksheet PDF

10276_Student1.pdf