1. Rocks - do they just “sit there?”
Mrs. Snyder
December 1, 2009

2. Earth’s surface
Think back to the Milky Way lab: Earth’s surface features do not remain the same. What causes them to change? Write your ideas.
Think about the time periods involved.
Do changes occur over long or short periods of time?
Create a table with three columns. Label these: Feature, Long, and Short.
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3. Data Table Features Long Short 1. Mountains 2. Canyons 3. Cliffs
4. Riverbanks
5. Shorelines
6. Caves
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4. Create your hypothesis
Look at the statue; check out the nose. What happened to it?
Make a list of your ideas describing how this change occurred.
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5. Background research!
You need to think about and find answers to these questions. Use the word document found here; visit the web sites on the worksheet to find answers.
Write your answers to the questions and keep these.
They will help you in our lab experiment.
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6. The question - review Are rocks able to dissolve?
Discuss your ideas with your partner.
Move to your assigned location with your partner
A - 1 with 9 B - 10 with 17
C - 2 with 15 D - 3 with 18
E - 4 with 12 E - 5 with 19
F - 6 with 11 G - 7 with 13
H - 8 with 14 & 16
Letters A through H are posted around the room to indicate where students are to work.This slide is the beginning of period 3 when Mrs. Johnson comes.
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7. Design an investigation
Brainstorm ideas about how this question could be investigated.
What type of experiment would investigate this question?
What materials would you need?
What would be measured?
How long would it take?
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8. Exploring the concept
Rainwater is not the same as the water you drink; it is a weak acid.
You will be looking at the effects of rainwater on the breakdown of rocks.
You will be putting chalk, (which is similar in composition to limestone) into vinegar,
Vinegar is a weak acid, much like rainwater.
You will observe the chalk over time to see whether or not the acid has any effect on the chalk.
You will also be putting chalk in water for comparison. (This will act as a control)
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9. Groups
Student groups are found below. Work at the location that has your group’s name.
Pebbles: 1, 4, 14, & 11
Grains: 2, 7, & 5
Basalts: 3, 18, & 13
Gems: 6, 9, & 17
Silicates: 8, 19, & 15
Galenas: 10, 12, & 16
Lab materials managers are those with the highest student number in each group.
These students will obtain materials from Mrs. S when directed to.
Make signs for each group. Position them around the room.
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10. Safety
What conventional safety precautions should we take during this investigation?
Do not to drink the water or vinegar.
Wash your hands when you finish.
What other precautions can you think of? (Safety managers are those students in each group with the lowest student numbers: 1, 2, 3, 6, 8, & 10).
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11. Directions
Cover desktops with newspaper, use masking tape to secure it.
Use the magnifying glass to examine each piece of chalk. Draw or describe what each piece of chalk looks like on the observation sheet.
Use the masking tape to write “acid” and put the label on the cup.
Use the masking tape to write “water” and put the label on the cup
Pour vinegar into one clear plastic cup until it is about 2/3 of the way full.
Pour water into one clear plastic cup until it is about 2/3 of the way full.
What will happen to the chalk after it sits in the vinegar for one hour. Record your prediction on the observation sheet.
Place one piece of chalk in each plastic cup.
Store the cups in a safe place (lab managers will bring labeled cups to the window sill when directed).
After 1 hour, examine the chalk with the magnifying glass. Draw or describe on the observation sheet what each piece of chalk looks like.
Predict what will happen to the chalk after it sits in the vinegar for a total of 24 hours. Record your prediction on the observation sheet.
After 24 hours, examine the chalk with the magnifying glass. Draw or describe on the observation sheet what each piece of chalk looks like.
On the observation sheet, write a conclusion that explains your observations.
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12. Materials inventory - check that you have …
vinegar
water
2 small pieces of chalk
masking tape
one permanent marker
one magnifying glass
paper towels
observation sheet
2 clear plastic cups
newspaper to cover desktops
safety goggles and apron or t-shirt
Lab to dissolve rock
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13. Discussion
1. Which piece of chalk changed the most, the one soaking in water or the one soaking in vinegar? Why?
2. How did the chalk change after soaking in vinegar for 1 hour? After 24 hours? What may have caused these changes?
3. Was there a greater change after 24 hours? Why?
4. How did your predictions compare with your results?
5. How does what you observed compare to what happens when rainwater falls on rocks?
6. How long does it take to dissolve rocks in nature?
Help students to understand that when rainwater mixes with carbon dioxide in the air or carbon dioxide in air pockets in soil, a weak acid called carbonic acid is produced. When carbonic acid flows through the cracks of some rocks, it chemically reacts with the rock causing some of the rock to be dissolved. Over many thousands of years, much rock can be dissolved.
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14. Study the diagrams 1. Describe the rocks in each picture.
2. What evidence would suggest that these rocks are undergoing chemical weathering?
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15. Digging Deeper
Chemical weathering is the decomposition of rocks due to chemical reactions occurring between the minerals in rocks and the environment. Following are examples of the chemical weathering processes.
Water is the main agent of chemical weathering. Water contains many weak acids, such as carbonic acid. This weak, but abundant, acid is formed when carbon dioxide gas from the atmosphere mixes with rainwater. Sulfur dioxide and nitrogen gases create other types of acids that act as chemical weathering agents. Some sources of sulfur dioxide are power plants that burn coal; as well as volcanoes and coastal marshes. Sulfur gases react with oxygen and rainwater to form sulfuric acid. Although relatively weak, this acid’s abundance and long term effects produce noticeable damage to vegetation, fabrics, paints, and rocks.
Oxidation is another kind of chemical weathering that occurs when oxygen combines with another substance and creates compounds called oxides. Rust, for example, is iron oxide. When rocks, particularly those with iron in them, are exposed to air and water, the iron undergoes oxidation, which can weaken the rocks and make them crumble.
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16. References
(Image for background)
(reference for the statue)
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