It doesn't have to rain for harmful acid rain to occur. Mist, fog, snow and even small dry particles can be acid rain -- precipitation with high sulfuric and nitric acid levels. Humans and nature create those acids by performing activities that cause water vapor to react with nitrogen oxides and sulfur dioxide. Volcanoes make it when eruptions release sulfur dioxide into the air. People compound the problem when they operate factories and drive vehicles that release harmful gases into the atmosphere. You can create projects that simulate acid rain using several methods.
If you are handling acids, use extreme care. Wear goggles and gloves to protect your eyes and hands. Take your time when adding drops of acid to other solutions.
Use Fire to Simulate Acid Rain
One way to simulate acid rain is to create it the way humans do -- pump sulfur into the air. After adding 5 ml of distilled water to a test tube, put a few drops of bromothymol blue solution into the water. Bromothymol blue is an indicator that turns yellow in an acidic solution. Put a few matches that have a high sulfur content into a glass jar, light them and close the jar. As the matches burn, they release sulfur gases and carbon dioxide. Remove the jar's lid when the matches go out and pour some bromothymol solution into the jar. Shake it briskly and note how the solution turns yellow indicating that the solution is acidic -- just like acid rain.
Set Up a Lake Experiment
Using a few chemicals and lab supplies, you can demonstrate the effect that vehicle use, factory gas emissions and other human activities have on lakes. Unlike the previous project, this one uses acids to recreate the pollution that creates acid rain. It requires bromothymol blue, pH paper with a range of 0 through 14, a 2 M solution of sulfuric acid, petri dishes, a 0.5 M solution of sodium nitrite and a 0.5 M solution of sodium sulfite.
Create Virtual Lakes
Add a few drops of bromothymol blue near the edge of a petri dish away from its center to create a puddle; this puddle represents a lake. Repeat the process to add a few more "lake" puddles in other parts of the dish. Put one drop of sodium sulfite in a location where no lakes exist. The sodium sulfite represents the gas that a power plant might emit.
Make the Acid Rain
You can now simulate acid rain by putting one drop of sulfuric acid in the sodium sulfite puddle and placing the petri dish's lid on it. Adding the sulfuric acid triggers the production of sulfur dioxide. Note how the "lakes" containing bromothymol blue turn yellow because bromothymol blue becomes yellow in acidic solutions. Place a piece of pH paper in one of the lakes to measure its pH. Measure the pH of other puddles that reside at various distances from the sodium sulfite source. Repeat the experiment using another petri dish containing lake puddles made of bromothymol blue. This time, use one drop of sodium nitrite as the gas source instead of one drop of sodium sulfite. Sodium nitrite simulates the gas vehicles might emit.
Precautions and Tips
Ask someone else to complete this project if you are allergic to sodium sulfite.
When analyzing your results, remember that a pH of 7 is neutral. Values less than 7 mean that your solutions are acidic, and values greater than 7 are basic.
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