Download Lab: Exploring Chemical Weathering

Lab: Exploring Chemical Weathering
Objective: To recreate the effects of chemical weathering on rocks of varying composition.
Materials:
Rock sample chips
Cheesecloth
balance
Procedure:
glass jars
graduated cylinder,
Dilute Hydrochloric Acid
(1) Put 4/5 chips in each jar. Rinse the rock chips with clean water to remove dust and loose
grains. Repeat several times for each sample.
(2) Find the mass of the rock fragments to the nearest gram.
(3) Measure 100ml of hydrochloric acid and pour into jar. The solution should completely cover
the chips.
(4) For the 2nd observation, pour off the acid solution. Use cheesecloth to make sure no rock
samples fall out of the jar.
(5) Rinse rocks several times with fresh water and drain.
(6) Measure the mass of the rock contents again. Record this information in the table.
(7) Add 100ml of hydrochloric acid to each sample jar and set aside until the next day.
(8) Follow the same procedure for 4 consecutive readings. Record results in data table.
Table- Rate of Weathering
Rock
Sample
Sample
1
Sample
2
Sample
3
Sample
4
Combined Combined
Mass
Mass
Day 1
Day 2
Net
Change
Combined
Mass
Net
Change
Combined
Mass
Net
Change
Combined
Mass
Net
Change
(1-2)
Day 3
(2-3)
Day 4
(3-4)
Day 5
(4-5)
Analysis and Conclusion:
1. Which of the 4 rock samples weathered the most? How does your data support this conclusion?
2. Which of the 4 rock samples weathered the least? How do you explain the result?
3. What properties of the samples may play a part in their resistance to chemical weathering? Which
property do you think was most significant?
4. Did the rate of weathering change in any of the samples during the course of the investigation? If so,
explain and suggest what may have caused this.
5. What primary process of chemical weathering does this exercise most closely simulate?
6. In addition to the difference of each of the 4 rock types, what other properties might influence the rate of
chemical weathering in each of the samples?
7. Which of the 4 rock types in this investigation would be best to construct a building in an area with
heavy industrial emissions and car exhaust? Why?
8. What are some examples of chemical weathering evident in your area? Describe what processes may
have been responsible for the weathering.