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Acid Rain and pH Visualization Lab

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Acid Rain and pH Visualization Lab Powered By Docstoc
					Name: __________________________ Class: _____________________ Date: _____________________


     Visualizing Differences in Rainwater pH Levels
Introduction
The pH scale is used to determine if a substance is an acid, base, or neutral. This is an important chemical
analysis tool of environmental science, as most living things have a specific range of pH levels they can thrive
in. While the scale is easy to understand, the actual differences between the pH levels is not.




   1. Given the examples shown above, what pH do you think would be ideal for a saltwater aquarium
      containing species of fish found in a coral reef? Justify your answer.


   2. What pH do you think would be ideal for the soil that most trees grow in? Justify your answer.

   3. What is the normal pH of pure rainwater? Would you consider this to be a strong or weak acid or base?


   4. Acid precipitation occurs when rain or snow falls that has a pH lower than is expected from pure rain.
      What kinds of effects would you expect to see on plant life from acid rain? On trees and other plants?




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Name: ___________________________ Class: ______________________ Date: ____________________

Acid Precipitation in the United States
This data is taken from the United States Geological Survey (USGS). Soil samples were taken from several
specific points around the United States. A pH measurement was made of each soil sample. Based on these pH
measurements, the following map was generated.




   5. What region of the country seems to have the biggest problem with acid precipitation?


   6. What is the lowest tested pH found anywhere on this map?


   7. What is the tested pH level of the soil in your area, based on this data?




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Name: ___________________________ Class: ______________________ Date: ____________________

Visually Comparing pH Levels
This lab will have you take several simulated acid rain samples and determine how much of each is required to
completely neutralize a given base.

Hypothesis:
  1. How much stronger of an acid do you expect the acid rain with a pH of 4.2 will be compared to normal
      rain with a pH of 5.6? Write a specific quantitative prediction below.

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Materials:
   Nine test tubes                                              Dropper bottle of
   Test tube rack                                                phenolphthalein
   Eight simulated rain samples (pH 5.6-4.2)                    Safety goggles
   Sodium hydroxide (NaOH)                                      Graduated cylinder

Procedure
   1. Label eight of the test tubes with the pH of the different rain samples. There should be eight samples
      ranging from a pH of 5.6 to 4.2.

   2. Put 10mL of NaOH into the unlabeled test tube.

   3. Add 3 drops of the phenolphthalein solution to the test tube. The solution should change color.

   4. Add one drop of the pH 5.6 rainwater sample to the test tube. Stir the test tube by lightly tapping it with
      your finger.

   5. Continue to add drops of the rainwater sample to the test tube until the color disappears. Record the
      total drops of acid added to the solution in your data table.

   6. Pour out the neutralized solution down the sink and rinse with water.

   7. Repeat steps #2-6 for the other rainwater samples.

Data

   Table 1: Drops of Rainwater Sample Needed to Neutralize NaOH
    Normal
                 Acid Rain Acid Rain Acid Rain Acid Rain                  Acid Rain     Acid Rain     Acid Rain
   Rain pH =
                  pH = 5.4     pH = 5.2    pH = 5.0      pH = 4.8         pH = 4.6      pH = 4.4      pH = 4.2
       5.6



   8. In this data set, what is the independent variable that you are controlling?


   9. In this data set, what is the dependent variable that you are measuring?
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Name: ___________________________ Class: ______________________ Date: ____________________

   10. Create a line graph based on your collected data. Remember, the independent variable should be on
      the x-axis and the dependent variable should be on the y-axis.




   11. Based on the graph you completed above, do the results support your hypothesis, or should it be
       rejected? Explain.

   12. Why are line graphs a good option when displaying data over time?


Conclusion

   13. On the surface, a difference between a pH of 4.2 and 5.4 does not seem very significant. Explain
       exactly how much stronger of an acid the 4.2 pH rainwater is compared with the 5.4pH rainwater.



   14. A common source of acid rain is air pollution that contains sulfur. This creates sulfuric acid when it
       mixes with water vapor in the air. Sulfur air pollution is easy to identify because it has a rotten-egg
       odor. What are some sources of sulfur air pollution you have encountered?



   15. Why does the Eastern mid-Atlantic region of the United States have the biggest problem with acid
       precipitation?

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DOCUMENT INFO
Description: This is a lab written for environmental science students comparing the pH levels of rainwater. Students will perform a titration of eight simulated rainwater samples with sodium hydroxide (NaOH) to get a more concrete sense of how much stronger of an acid different pH levels are.
About I teach high school and college level biology, chemistry, and environmental science. Visit my main website at www.aurumscience.com to see my full collection of resources.