Climate and Chemical Weathering Lab 2013
Whether it's the granite of a New Hampshire mountain breaking down into sand
and clay or the limestone of Kentucky decomposing to form rich soil, all chemical
weathering processes involve water. What effect does the temperature of the water have
on the rate at which chemical weathering occurs?
Carbonic acid is a weak acid that forms when carbon dioxide dissolves naturally
in rain, in streams, or in groundwater. A common chemical weathering process is the
reaction between carbonate rocks (such as limestone and marble) with carbonic acid. In
this lab activity, you will observe a model of this reaction. By changing the temperature
of the water, you can model the effect of the temperature on the rate of the reaction
between carbonate rocks and carbonic acid.
Objectives
1. To model a chemical weathering process.
2. To graph the data from the model and to interpret the graph.
3. To predict what will happen when the model is modified.
Materials
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3 -250 mL beakers
thermometer
3 - effervescent antacid tablets
hot water (40 - 50 degrees C)
warm water (20 – 30 degrees C)
ice water (0 - 10 degrees C)
stopwatch
map of Earth's Climates (Classroom Atlas Book)
Procedure
1. Arrange 3 beakers in a row. Assign each beaker a number from 1 to 3. Each
beaker should contain about 200--mL of water. The water temperature in each
beaker will need to be adjusted to match the following: Beaker 1, hot water (40 50 degrees C), Beaker 2, warm water (20 – 30 degrees C), and Beaker 3, ice water
(0 - 10 degrees C).
2. Begin with Beaker 3. Remove any pieces of ice from the water. Check to be sure
that the water is within the correct temperature range and that the thermometer
has stopped changing. Read the temperature of the water in Beaker 3 to the
nearest half degree and record it on Data Table A. Remove the thermometer from
the beaker and set it aside in a safe place.
3. Read this whole step twice before beginning the step. (Continued on next
page)
a. Drop the antacid tablet into Beaker 3. Start timing (seconds) at the instant
the tablet enters the water. Stop the timing when the last piece of the
tablet dissolves. (You do not need to wait for all of the bubbling to stop;
wait only for all pieces of the tablet to disappear.)
b. Record the time to the nearest whole second on Data Table A.
Climate and Chemical Weathering Lab 2013
4. Repeat the steps 2 and 3 for each of the remaining 2 beakers using the correct
temperature ranges.
5. Copy the temperature results you have for Beaker 1 from Data Table A to Data
Table B. The remaining values in Data Table B will need to be calculated. For
the temperature values; add 10 to the reading for Beaker 1 and record that as the
temperature for Beaker 2. In the same way, add 10 to the beaker 2 temperature
and record that as the Beaker 3 temperature.
6. Copy the time results you have for Beaker 1 from Data Table A to Data Table B.
The remaining values in Data Table B will need to be calculated. For the time
values; the time for Beaker 2 will be one half of the time for Beaker 1 and the
time for Beaker 3 will be one half of the time for Beaker 2. When you divide the
values, round off each result to the nearest whole second.
7. Plot a graph of the data. Make sure you know what the independent (y-axis)
variable is and what the dependent (x-axis) variable is. “Which variable is
dependent on the other one?”
**** You’ll need to work on
the Climate Information
with the Atlas’ in class and
save the graphing part for
after you’ve completed the
Atlas work!
Climate and Chemical Weathering Lab 2013
Name: _________________________________ Date: ______________ Class: ______
OBSERVED DATA (Data Table A)
(Observed = what you actually see happening)
Beaker Number
Temperature (ºC)
Time (s)
1-A
2-A
3-A
THEORETICAL DATA (Data Table B)
(Theoretical = what you might see happening in an actual experiment)
Beaker Number
1-B
2-B
3-B
Temperature (ºC)
1A temp =
10 + 1-A temp =
10 + 2-B temp =
Time (s)
1A time =
½ 1-A time =
½ 2-B time =
Graph both your Observed and Theoretical Data. Be sure to put the correct variables in
the correct places on your graph. You know, Dependent and Independent Variables!!!
Which variable depends on the other? Use different colors to show Observed and
Theoretical.
Climate and Chemical Weathering Lab 2013
Analysis and Conclusions
1.
a) In which beaker did the reaction occur most slowly? _________________
b) In which beaker did the reaction occur most rapidly? _________________
c) What do you think is the relationship between the temperature and the rate
of a reaction in the experiment?
2.
Based upon your observations, what do you think is the relationship between the
climate and the rate of natural chemical weathering?
3. Turn to the map of climates on pages 36 and 60 in Classroom Atlas provided.
Locate Rio de Janeiro in South America and Seattle in North America. The map
key indicates that both cities have climates with abundant moisture.
a) Recall what you know about carbonic acid in rain and in groundwater.
Compare the weathering rate of a limestone in Rio de Janeiro with that of
a limestone in Seattle. Is there a difference? Explain your answer.
4. Now locate Barrow, Alaska, use the map on page 34 in the Atlas to see where
Barrow is! Then turn the page (pg 36) to determine the climate in Barrow.
b) Why is a limestone in Barrow likely to weather very slowly
5. How would the rate of the reaction have been different if the tablets had been
ground into a powder before they were dropped into the water?