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ESS Unit 8 Weathering Lab Names ___________________________________________ Period ________ MECHANICAL WEATHERING Station 1/2 Prediction: _____________________________________________________________ ________________________________________________________________________________ Data Table 1 Weathering of Different Size Marble Chips Weathering time Mass of marble chips (g) Observations: (min.) Large small Size, shape, water color 0 3 6 9 12 15 (Line) Graph 1 Mass of Large and Small Marble Chips vs. Time 20.0 Mass of Chips (g) 19.5 19.0 18.5 18.0 17.5 17.0 0 3 6 9 12 15 Time (min.) Part 1 Questions 1. What is the effect of TIME on the rate of weathering? 2. What was the PERCENT change in mass of the LARGE marble chips compared to the SMALL chips? Loss in mass x 100 Original mass loss in mass x 100 original mass 3. How does the amount of surface area exposed contribute to weathering (pg. 262) 4. What do you think would happen if you continued shaking the marble chips for 24 hours or longer? ESS Unit 8 Weathering Lab Names ___________________________________________ Period ________ Station 3/4 Prediction:_____________________________________________________________ ________________________________________________________________________________ Data Table 2 Change in Mass of Rocks with Different Composition/Hardness Hardness on Initial Final Mohs scale Mass (g) Mass (g) Observations Rock Type Sandstone Halite (rock salt) (Bar) Graph 2 Change in Mass vs. Rock Type 25 g 20 g 15 g 10 g 5g 0g Initial Final Sandstone Rock Initial Final Halite Part 2 Questions 1. How did the change in mass of the sandstone compare to the change in mass of the halite? 2. Sandstone is composed of the mineral quartz, use the table on page 701 in your text to find the hardness of the two minerals 3. Explain the relationship between the hardness and the amount of abrasion, as observed in the activity? 4. What conclusions can you draw between the results obtained in this activity and the natural process of weathering that takes place in nature? ESS Unit 8 Weathering Lab Names ___________________________________________ Period ________ CHEMICAL WEATHERING Station 5/6 Prediction: _____________________________________________________________ ________________________________________________________________________________ Data Table 3 Chemical Weathering of Rocks with Different Composition Time Observations / Descriptions Limestone Granite Chalk Composition At the start 15 minutes later Part 3 Questions 1. What changes did you observe in each sample? 2. What evidence(s) did you observe to support the idea that a chemical change occurred? 3. How is the composition of granite (page 118) different from the minerals in limestone or chalk (page 107)? 4. How does a weak acid effect rocks in nature? ESS Unit 8 Weathering Lab Names ___________________________________________ Period ________ Station 7/8 Prediction: _____________________________________________________________ ________________________________________________________________________________ ```````` Data Table 4 3 Chemical Weathering of Pyrite and Granite Time Observations Pyrite Chips Water/Acid Solution Granite Chips Water/acid Solution Start Days later Days later Part 4 Questions (use pg. 261 in text) 1. What changes did you observe that would indicate that chemical weathering took place? What is the chemical formula for pyrite? What substance in pyrite caused the chemical change? 2. Label the substances and BALANCE the chemical equation for the oxidation of iron: Fe _______ 3. + O2 ________ Fe2O3 ____________ Label the substances in the chemical equation for forming carbonic acid (acid rain) H2 O ___________ + CO2 _____________ H2CO3 ______________ 4. How does HYDROLYSIS contribute to the chemical weathering of rocks? (pg 260) ESS Unit 8 Weathering Lab Names ___________________________________________ Period ________ While participating in the class post-lab discussion on the results of the weathering lab, complete the analysis questions below: 1. What is the effect of time on the rate of weathering? 2. How did the mass of the rocks/minerals change over time? Give an example using the rocks. 3. Based on the results from STATION 1/2, how did different particle size of rocks affect the weathering? 4. From STATION 3/4, explain the relationship between hardness of the minerals in the rock and the amount of abrasion that occurs. Give an example using two rocks with different hardness. 5. Which of the different rock/mineral samples had the largest change of mass? The least? Use the composition of the minerals to explain. ESS Unit 8 Weathering Lab Names ___________________________________________ Period ________ 6. Describe what would happen if you continued to shake/weather the rocks in water for 24 hours or longer 7. Which rock/mineral was weathered by the weak acid (rain)? What is it composed of? Why is granite resistant to chemical weathering in acid? 8. What evidence did you observe to support the idea that a chemical change occurred when rocks like are exposed to acid (rain)? 9. Explain how hydrolysis contributes to the chemical weathering of rocks. 10. What is the difference between mechanical weathering and chemical weathering? ESS Unit 8 Weathering Lab Names ___________________________________________ Period ________ Chemical weathering weathering Mass of chips (g) time Amount of calcite Degree of abrasion Rounding of fragments Hardness on Mohs scale Time in river/stream Chemical weathering Particle size weathering Amount of quartz in the rock ESS Unit 8 Weathering Lab Names ___________________________________________ Period ________ 1. What is the major type of weathering in Washington D.C. where AYT is 23°C and AYP is 104 cm? 2. If AYT in D.C. dropped 26°C but the AYP stayed the same, what kind of weathering would dominant? 3. Phoenix, AZ. Has an AYT of 20°C and an AYP of 20 cm. How would the climate in Phoenix have to change for moderate chemical weathering to become dominant? 4. According to the graph, no frost action occurs at a AYT above 13°C. Why? 5. In general, how does a climate with strong chemical weathering differ from a climate with strong mechanical weathering?