Investigation 1 – Earth is Rock Part 2: Grand Canyon Rocks Part C continued

The Grand Canyon Introduce the Grand Canyon Remind students that the last location they viewed in “Landforms Tour” was the Grand Canyon. Show students the map of the southwest United States and point out the location of the Grand Canyon. Tell students, “The Grand Canyon is a site that is famous for its geology. It is known as one of the most spectacular landforms on Earth. The Grand Canyon is considered to be one of the seven wonders of the natural world. Over 4.5 million people visit Grand Canyon National Park each year. It is considered by many geologists as an important place to begin studying geology.”

Discuss the first sort Refer to your data table in the mini journal What did categories did you identify? 5. Discuss the first sort After 5 minutes or so, have several groups report the ways they sorted the rocks. Categories that students might consider include color, lightness/darkness, sandiness, presence of fossils, roughness, or hardness. When a group has reported their results, ask the other groups if they came up with the same method or have something new.

Wear goggles at all times If any acid gets on you, inform your teacher Safety! Wear goggles at all times If any acid gets on you, inform your teacher 26. Introduce the acid test After students have reported their first sorting results, explain that one important field test that geologists often perform on rock samples is an acid test. Hold up one of the dropper bottles of acid and tell students, “This bottle contains dilute hydrochloric acid. You should treat this chemical with respect and take safety seriously. If you get some on your hands, wash and dry your hands. This is so you won’t accidentally get the acid in your eyes.” Distribute safety goggles to students.

Acid Test Place the rock on a paper towel, number side down. Write the number on the towel. Squeeze one drop of acid from the bottle onto the rock. Only one drop is needed per rock. Observe what happens. You might want to use the hand lens for a better view. Record your observation in your notebook. You can use the “Other” column in your data table and label it “Acid Test” Use the paper towel to dry the rock. 27. Model the acid test Select a rock from one of the boxes and model the acid-test procedure as you describe it to students. Place the rock on a paper towel, number side down. Write the number on the towel. Squeeze one drop of acid from the bottle onto the rock. Only one drop is needed per rock. Observe what happens. You might want to use the hand lens for a better view. Record your observation in your notebook. You can use the “Other” column in your data table and label it “Acid Test” Use the paper towel to dry the rock. Each group will have a bottle of acid. Remind students to use only one drop of acid- they don’t need any more. There are enough rocks in each set for each person to have a turn doing the acid test. Have Getters get one bottle of acid, two pairs of goggles, and a paper towel for each pair of students.

You have about 10 minutes to complete the acid test Once finished, return rocks and acid bottles to the materials station 28. Complete observations Give students about 10 minutes to complete the acid test. They should record observations in their data table. Ask the teams to return the rocks to the boxes, and have Getters return the rocks and acid bottles to the materials station.

Base your sorting upon the results from the acid test Sort rocks again Base your sorting upon the results from the acid test 29. Sort the rocks again Ask students to sort their rocks again, this time using the results from the acid test.

Discuss rock groups How did the appearance of the rock change after you applied the acid? Into how many groups did you sort the rocks from Mile 20? Into how many groups did you sort the rocks from Mile 52? Which properties did you use to sort the rocks? 30. Discuss rock groups Ask if the acid-test observations changed they sorting in any way. Ask, “How did the appearance of the rock change after you applied the acid? [It got wet. It fizzed. Acid soaked into some of the rocks. Acid slid off other rocks.] Into how many groups did you sort the rocks from Mile 20? Into how many groups did you sort the rocks from Mile 52? Which properties did you use to sort the rocks?” [Fizzed in acid, sandy texture, color, smooth texture, contained fossils.]

Which of the rocks in both sets fizzed when you placed acid on them? Rocks that fizzed Which of the rocks in both sets fizzed when you placed acid on them? Did these rocks share any other properties? CaCo3 31. Discuss the rocks that fizz Ask, “Which of the rocks in both sets fizzed when you placed acid on them?” [Usually 4, 5, 9, and 10.] “Did these rocks share any other properties?” [Mostly smooth or fine-grained texture.] Tell students, “The material in the rock that reacted with the acid is calcite. Calcite is a common mineral composed of calcium, carbon, and oxygen. Calcite’s chemical formula is CaCo3. (Write formula on board) This particular combination of carbon and oxygen is called a carbonate. Calcium carbonate is found naturally as calcite and as chalk. When the acid reacts with calcite, a chemical reaction occurs and a gas, carbon dioxide, is given off, hence the fizzing. When geologists place acid on a rock and it fizzes, they can be pretty sure that calcite is one of the minerals in the rock.”

Rocks that contain calcite Limestone Rocks that contain calcite 32. Introduce limestone Tell students that the name geologists give to rocks containing calcite is limestone. The four rocks that fizzed are all samples of limestone.

Which properties do these two rock samples share? Sandy Rocks Which properties do these two rock samples share? Did either of them fizz when you dropped acid on them? What do you observe if you gently rub these two samples together? 33. Discuss the sandy rocks Have students refer to their notes on rock 8. Ask them what other rocks they included in the group with 8. [6, the other sandstone.] Have them compare rocks 6 and 8. Ask, “Which properties do these two rock samples share? [Sandy, rough.] Did either of them fizz when you dropped acid on them? [No.] What do you observe if you gently rub these two samples together?” [Sand-sized particles fall off.]

Rocks made out of sand particles cemented together Sandstone Rocks made out of sand particles cemented together Samples 6 and 8 are examples of sandstone 34. Introduce sandstone Tell students that the name geologists give to rocks that are made out of sand particles cemented together is sandstone. Rocks 6 and 8 are both samples of sandstone.

Did rock 7 fizz when you placed acid on it? Shale Did rock 7 fizz when you placed acid on it? What type of texture does 7 have? What other properties does 7 have? Shale is a sedimentary rock made of clay or silt 35. Identify shale Rock sample 7 is the only one without a group. Ask, “Did rock 7 fizz when you placed acid on it? [No, and it didn’t soak in; it’s not limestone or sandstone.] What type of texture does 7 have? [Smooth.] What other properties does 7 have?” [Contains leaf fossils, is black.] Explain that rock 7 is called shale. Shale is a smooth-textured rock that doesn’t fizz in acid. Walk around the class with the cup of clay and let students stick a finger in, then rub their fingers together to feel the clay. Just like sandstone has the texture of its particles, sand, shale has the smooth, slick texture of its particles, clay.

Time to Record Go back to notebooks, identify the rock samples with the appropriate name 36. Record rock names in notebooks Ask students to go back to their notes and identify the rock samples with the appropriate name by adding the information to their data tables.

Review vocabulary from this part Record Vocabulary Review vocabulary from this part Add vocabulary words and definitions to your notebooks Update vocabulary indexes 37. Record vocabulary Take a few moments to review the vocabulary developed in this part. Ask students to add vocabulary words and definitions to their notebooks, and to update their vocabulary indexes if they haven’t done so already. Calcite Elevation Limestone Sandstone Shale

Question Why would a geologist consider a bottle of hydrochloric acid and a hand lens two of their most important tools in the field? 38. Discuss geology tools Ask students to write the answer to this question: Why would a geologist consider a bottle of hydrochloric acid and a hand lens two of their most important tools in the field? Spend a few minutes discussing students’ answers. [The acid test detects calcite in a rock sample. The hand lens provides a close look at the particles in a rock. This information helps geologists identify the kind of rock they have.] 39. Clean up Have Getters return materials to the materials station.

Homework Summarize what you learned about Powell in a mini-report http://www.fossweb.com/delegate/ssi-wdf-ucm- webContent/Contribution%20Folders/FOSS/multimedia_ms_1E/Earth History/media/slideshow_prt.htm 40. Extend the investigation with homework Students can access “Powell’s River Trip” through FOSSweb. Ask them to summarize what they learned about Powell in a minireport. This is a nice history connection. Photos come from the National Archives and are from Powell’s second expedition (1871-1872).