Normal unpolluted rain water has a pH of 5.6 to 5.7 due to natural emissions (volcano, forest fires caused by lightning, and decaying organic matter) and the carbon dioxide (CO2) normally present in the air. The acid in acid precipitation is due to sulfuric acid and nitric acid formed when sulfur dioxide and nitrogen oxides react with water vapor in the atmosphere. These oxides are common gaseous by-products of man.
You will demonstrate how gases that are dissolved in water will turn the water into an acid.
Answer the following quiz question, and view the results of other students.
Go to the "Acid rain and Me?" bulletin board and add a new message to answer one of the following questions:
During this experiment you and your partners will be making a model of how acid rain is made in the Earth's atmosphere. Collect the equipment from the list above from your teacher and do the following experiment.
1. Add drops of bromothymol blue to 5 ml of distilled water in a test tube until the water becomes a light blue color. In the presence of an acid, bromothymol blue will turn yellow.
2. Place several matches in a glass jar. Light the matches. Cover the jar with its lid. The matches will give give off carbon dioxide (CO2) and sulfur gases.
3. Allow the matches to burn out. Add bromothymol blue from the test tube to the jar. Replace the jar's cover, and shake the jar vigorously.
4. Observe what happens inside the jar.
Discuss the following questions in your lab group or with your teacher:
1. What changes, if any, happened to the color of the bromothymol blue?
2. What do the changes or lack of changes mean?
3. What could have caused changes or lack of changes to occur?
Go to the "Acid rain and Me?" bulletin board and write a new message to answer the following question about your experiement:
1.Where does acid rain usually form, and how does it form?
2. What is meant by "dry deposition"?
You have made a model of how gases can dissolve in water to make the water more acidic. You have also discovered how acid rain is formed. In another lesson, you will learn about human activities that produce gases that make acid rain.