For each group of 3
3 Student Activity Sheets for Learning Experience 6
Plaster of Paris
2 deli containers
For the class:
Read the background information in the Rocks, Minerals, and
Landforms Teacher’s Manual. (Please see PDF
Student should observe or recall evidence of the effects of
The Plaster of Paris will need to be mixed prior to this
Students will be able to identify the various forms of
weathering and their effects on landforms.
Students will describe the causes and effects of physical and chemical weathering
What causes rocks to
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.)
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
How long do you think it took for these changes to occur?
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.
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?
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.
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.
SHEET for Learning Experience 6
Follow the directions below to complete the activities
illustrating physical and chemical weathering.
Divide a large piece of chalk into three pieces.
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?
Pour the water into a jar and drop two pieces of chalk into
Wait for 3 minutes then observe.
What happened to the chalk in this jar?
Compare the results of the chalk in the vinegar to the two
pieces of chalk in the water.
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
*Put your model rock in the freezer for one night.
Predict what you think will happen to your model rock in the
My model rock looked like this after I put it in the
What did I learn about the weathering of rocks from these