Learning Experience 6: Weathering

TEACHER’S GUIDE

Materials:

For each group of 3 students:

3 Student Activity Sheets for Learning Experience 6

Medicine cup

Balloon

Plaster of Paris

2 deli containers

Chalk

Craft stick

Water

Paper towel

For the class:

Vinegar

Plastic jar

Freezer

Water

Preparation:

Read the background information in the Rocks, Minerals, and Landforms Teacher’s Manual. (Please see PDF)

Session 1:

Student should observe or recall evidence of the effects of weathering.

Session 2:

The Plaster of Paris will need to be mixed prior to this learning experience.


Basic Skills Development:

Creating models

Discussing

Predicting

Observing

Describing

Evaluation Strategy:

Students will be able to identify the various forms of weathering and their effects on landforms.

Vocabulary:

weathering

erosion

sediment

soil

deposition

Objective: Students will describe the causes and effects of physical and chemical weathering on landforms.

What causes rocks to break down?

Session 1

Take a walk on the school grounds to look for signs of weathering. Students can look for deltas of soil deposited in areas along sidewalks, gullies cut into steep slopes, wind-deposited collections of sand, leaves, twigs, and trash in the process of becoming new soil, cracks in the pavement and/or buildings, worn corners on buildings and/or steps. (Students may see more of the effects of weathering after a rainstorm.)

Discussion Questions:

Do you notice any evidence of change to the school building? What do you think caused it?

Do you notice anything about the ground around the schoolyard? What do you think caused it?

Were these things exposed to sun? rain? wind?

Is there an area of the building or school grounds that is protected?

How long do you think it took for these changes to occur?

Session 2

Student groups will examine closely some of the effects of chemical weathering and physical weathering. Students should observe the effects of vinegar on chalk (chemical weathering), and the effects of water on chalk (physical weathering). The physical weathering test will be demonstrated by the teacher. Students should record information on their Student Activity Sheet for Learning Experience 6.

Discussion Questions:

How did the chalk change as a result of the vinegar?

Did the chalk change in its composition?

How is this similar to the effects of acid rain?

Give an example of when you have seen the effects of acid rain on rocks, statues, buildings, etc. Describe its effects.

What were the results of the physical weathering activity?

Did the chalk change in composition?

Session 3

Explain to students that another form of physical weathering occurs due to water and temperature. Give each group of students a balloon and two deli containers. They are to fill their balloon with water to the size of a golf ball. Students are to then mix two parts Plaster of Paris to one part water on one side of their deli container. They are to then cover the balloon with Plaster of Paris with the craft stick and allow it to dry on the other side of the deli container. (Remember: the thicker the layer of plaster, the longer it takes to dry.) The Plaster of Paris is representing a rock and the water in the balloon is representing the water that gets into the cracks of rocks. The left over Plaster of Paris can be discarded and the other deli container with the balloon can be put into the freezer. Students are to compare their model rock to a real rock then put their model rock in the freezer over night. Ask students to predict what they think will happen to their model rock, and have them draw a picture of their model rock before they put it in the freezer. The next day, examine the rocks and graph the number of rocks that were broken and which were not broken. They can draw a picture on their Student Activity Sheet for Learning Experience 6 of what happens to rocks when water seeps into their cracks and freezes.

Discussion Questions:

Do you think water can break rocks? Explain.

What state does water change into when it is put in the freezer? (liquid to solid)

What happens to water when it freezes? (it expands)

What other ways does water effect rocks? (water running over rocks, water dripping on rocks) Explain its effects.

Why do you think that some of the model rocks broke and other did not? (less water inside, more plaster around them)

Students could go on a second walk around the schoolyard looking for the effects of physical and chemical weathering that they did not notice before the learning experience.

STUDENT ACTIVITY SHEET for Learning Experience 6

Name _____________________


WEATHERING

Follow the directions below to complete the activities illustrating physical and chemical weathering.


Divide a large piece of chalk into three pieces.


Chemical Weathering Test


Pour 30 ml of vinegar into a medicine cup.


Pour the vinegar into a medicine and drop a piece of chalk into the vinegar.


Wait for 3 minutes then observe.


What happens to the chalk in the vinegar?

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Physical Weathering Test

Pour the water into a jar and drop two pieces of chalk into the water.


Wait for 3 minutes then observe.


What happened to the chalk in this jar?

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Compare the results of the chalk in the vinegar to the two pieces of chalk in the water.

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Water Freezing Test

*Make a very small water balloon.

*Cover the water balloon with Plaster of Paris so it looks like a “rock”.

*Let your model rock harden.


How is your model rock like a real rock? How is your model rock not like a real rock?


Before I put my model rock in the freezer, it looks like this.






*Put your model rock in the freezer for one night.


Predict what you think will happen to your model rock in the freezer.

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My model rock looked like this after I put it in the freezer.






What did I learn about the weathering of rocks from these experiences?

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