Lab: Acid Rain and Weathering Rate
Question: Does increasing CO2 levels in our atmosphere, also increase the rate at which
weathering occurs, adding to sedimentary basins?
In this lab, you will be modeling and making observations of the processes that contribute to acid rain formation.
Taking what you learn, you will set up an experiment (with a control) to determine if acid rain has an effect on the
rate of weathering of sandstone.
Possible Indicator Choices:
Materials:
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20 mL of distilled water
100 mL graduated cylinder
Plastic drinking cup
Plastic tube
Indicator solution of your choice
pH paper (hydrion)
600 mL beaker
Ice
Timer
Probeware
Indicator
Bromophenol blue
Methyl orange
Phenolphthalein
Color in acid
yellow
red
colorless
Conversion Range
3.0–4.6
3.1–4.4
8.3–10.0
Color in Base
purple
yellow
fuchsia
Safety:
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Caution using glassware
Caution with chemical indicators…do not ingest
Do not blow after someone else on the plastic tubing
Do not set tubing down on lab table, without paper towel beneath it
Cup with
indicator
Ice water bath
Part A Procedures:
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Rinse all glassware
You will need to build a data table that can contain
the following data:
Measure 20 mL distilled water using graduated cylinder
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Initial pH of solution from pH paper
Fill plastic drinking cup with 20 mL distilled water
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Initial pH of solution using Probeware
Place Ice and water (from tap) in 600 mL beaker. Fill half-way
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Time
Rest cup of distilled water in ice-water bath
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Qualitative data
Useing pH paper (hydrion) and the probeware, determine the initial pH of
the water. Record in data table of your own design
7. Add 10 drops of your chosen indicator solution into drinking cup with
distilled water
8. Swirl gently to mix
9. Begin timer. Using plastic tube, blow continuously into distilled water cup with indicator solution until acid color change
is noted. Record how long it took. Note any color change as qualitative data, and record in data table.
10. Test pH again, using both hydrion paper, and probeware. Record results.
To get the carbon dioxide from our breath to dissolve in the water, we are going to blow through a straw into a cup of water, resting within a
beaker containing ice water. Why the ice water bath? Because gases dissolve in cold water far faster than they do in warm, or even room
temperature water. The concentration of CO2 in a breath that we exhale from our lungs is about 4% (4 CO2 molecules with the remaining 96
being nitrogen, oxygen, and water). Our emissions aren’t nearly as detrimental to the environment, as say an automobile, which contains 12%
After observing today’s activity, you are to design an experiment that will test if acid rain (carbonic acid)
influences the rate of weathering. We will use any of the rock specimens you used in your mechanical
weathering lab. Things to consider:
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What will be your control?
Making a hypothesis
Which sample?
How acidic should you make it?
Make the first three procedures
Think safety!
Design data tables
Be ready to do it tomorrow!
Go for it!
Analysis Questions
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Calculate the rate of weathering in each sample…the control, and the experiment.
Graph your results.
Which sample lost more mass?
If you had been able to do this lab in multiple phases, over many days, how do you think the
results would have differed?
If you had exposed one of your samples to a base, instead of an acid (like ammonia), how do you
think your results would have differed?
What was the purpose of the water in your experiment?
In your journal, don’t forget to indicate the following:
a. Dependent variable
b. Independent variable
c. Control
d. Constants
Why do you think part A of this lab failed so miserably?
If we had been able to create carbonic acid with our breath, and used that instead of the acid
you choose, do you think your results would have been different?