Earth ScienceName______

Chapter 12Period______

LabDate______

______

Weathering Rocks

In this lab, we will explore how mechanical and chemical weathering breaks down rocks. In Part I, we will investigate how cold water and agitation weathers rock, and in Part II, we will compare how warm, acidic water and agitation affects the weathering of rocks.

Part I

1. Mass out 25 g of limestone pebbles.

2. Place the chips into the plastic bottle and add enough cold, tap water to cover the pebbles in the bottom of the bottle.

3. Shake the bottle vigorously for two minutes.

4. Uncap the bottle and pour the water and rock through a strainer into a beaker. Rinse the rocks off with a little more water. Blot them dry on a paper towel. Try to get them as dry as you can. Note: You can now dump out the water you just strained into the sink.

5. Again determine the mass of the pebbles and record it the data table on the next page.

6. Repeat steps 2 through 5 until you have conducted a total of ten, 2-minute shakes. Be sure you record the mass of the pebbles before and after each shake. When you are done you will have found how much you have weathered the rock for each two-minute interval, and how much your weathered the rock for a total of 20 minutes of shaking. (2.5 points for conducting the experiment, 2 points for correctly recording data)

Part II

1. Repeat steps 1 thru 6 above using the special “Earth Science Water” I provide. Don’t forget to use new water for each shake. (2.5 points for conducting the experiment, 2 points for correctly recording data)

Part III

1. Complete the statement relating how the mass changed as shaking time increased. (1 point total)

2. Graph the data for shaking time (x-axis) verses final mass (y-axis) for Part I. Draw a best-fit straight line through the points and label your line Part I. (2.5 points)

3. On the same graph but using a different colored pencil, graph the data for shaking time (x-axis) verses final mass (y-axis) for Part II. Draw a best-fit straight line through the points and label your line Part II. (2.5 points)

4. Answer the analysis questions. (4 points total)

Pre-Lab

1. Brainstorm and write below a list of five factors that will affect the weathering of your limestone pebbles in this experiment? (1 point)

2. Create a 10 frame cartoon illustrating in detail the procedure of this lab. Do or draw this however you would like, just somehow include the steps of the procedure…the sky is the limit on the creativity here! Draw your cartoon on the back of the last page of this lab. (5 points)

Note: You will have to show us your completed pre-lab tomorrow before beginning the lab. (25 points total for the lab)

Data Table

Record the information you gather from the lab in the table below. (0.10 points each blank, 4 points total)

Data Table 1
Total
Shaking Time
(minutes) / Part I / Part II
Original Mass
( g) / Final Mass
(g) / Original Mass
( g) / Final Mass
(g)
2
4
6
8
10
12
14
16
18
20

Statement of Mass Verses Time

Complete each statement below. (0.5 points each)

1. Looking at the data from Part I of this lab, as the shaking time increased, mass ______.

2. Looking at the data from Part II of this lab, as the shaking time increased, mass ______.

Analysis Questions

Using graph paper, graph shaking time verses total mass for Parts I and II, as given in the instructions on the first page of this lab, then answer the following questions. (0.5 points each)

1. What happened to the mass of the rock material after each period of shaking in Part I? … in Part II?

2. What was the total change in mass of the rock from the beginning to the end of the shaking in Part I? … in Part II?

3. Which set lost more total mass over the length of the activity?

4. What were some of the factors in this activity that affected the rate that the pebbles were mechanically weathered? Please list at least 2.

5. Where on Earth would you find rocks undergoing weathering similar to this activity?

6. The “Earth Science Water” used in this activity was slightly acidic. In nature, how does water become slightly acidic?

7. In which Part, Part I or Part II, did the rocks weather faster? How does your graph show this?

8. What are some factors that would affect the mechanical weathering rate of rocks outside of your home?

Graph

Graph the data from Parts I & II below.