Creating Acid Rain
Background:
Acid Rain is defined as any type of precipitation
with a pH
of below 5.0. Normal rain has a pH which can range between 4.5 and 5.6 with an
average value of 5.0. This natural acidity is caused by dissolved carbon dioxide dissociating to
form weak carbonic acid. Acid rain is also caused by sulfur from
volcanic venting or impurities in fossil fuels,
and nitrogen
from the air, combining with oxygen to form sulfur
dioxide and nitrogen oxides. These diffuse into the
atmosphere and react with water to form sulfuric
and nitric acids
which are soluble and fall with the rain. Some hydrochloric
acid is also formed. The resulting increased acidity in soil and waterways
has proven to be harmful to fish and vegetation. Acid rain also accelerates weathering
in carbonate rocks and accelerates building weathering. It also contributes to
acidic rivers, streams, and damage to trees at high elevation.
Purpose:
In this activity, students will be able to:
q
Observe
the creation of acid rain
q
Analyze
the chemical equation for acid rain
q
Acknowledge
that acid rain can be created in many ways.
Materials:
600
mL Beaker
Distilled water
pH
meters
Straw
Stopwatch
Hypothesis:
Procedure:
Part One: One Person
1)
Fill the 600 mL Beaker with 300 mL of water.
2)
Place the pH meter in the water and record the initial pH in Table A. Keep the
pH meter in the water.
3)
Now, place one straw in the water. Have one student begin blowing
into the straw. Keep the student blowing into the straw for two minutes. Record
the pH of the water every 15 seconds.
4)
If the person gets tired, quickly exchange the person for a new group member.
Procedure:
Part Two: 2 People
5)
Repeat steps 1-4. However, instead of one person blowing, add another straw so
that now 2 people are blowing into the water at the same time.
6) Record initial pH and the pH measurements for the next 2 minutes. Swap people if a student becomes tired.
7)
Record all measurements into Table B.
8)
Answer the questions in the Analysis section.
Data:
Table A: One Person
|
|
pH
Measurement |
|
Initial
pH |
|
|
15
sec |
|
|
30
sec |
|
|
45
sec |
|
|
1:00
min |
|
|
1:15
min |
|
|
1:30
min |
|
|
1:45
min |
|
|
2:00
min |
|
Data:
Table B: Two People
|
|
pH
Measurement |
|
Initial
pH |
|
|
15
sec |
|
|
30
sec |
|
|
45
sec |
|
|
1:00
min |
|
|
1:15
min |
|
|
1:30
min |
|
|
1:45
min |
|
|
2:00
min |
|
Graph:
Make
a line graph of the 2 outcomes in the space below. Place the time on the x-axis
and place the pH measurement on the y-axis. You will have 2 separate lines, so
please make sure to label each line.
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Questions:
Answer in complete sentences
1)
Did the pH increase or decrease as the experiment progressed? Why did this happen?
2)
Record the chemical equation of the reaction of this experiment in the space
below. Make sure to balance the equation.
3)
Compare and contrast one person versus 2 people blowing into the straw.
4)
Does this process occur naturally or anthropogenically in the environment?
Explain.
5)
How does carbon dioxide get into the air naturally? Anthropogenically?
6)
What would happen if you placed the water after the experiment on a plant?
Explain the effects.
: