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Contributed by: Connecticut Academic Performance Test (CAPT)
A group of students prepared a vinegar-and-water solution to simulate
acid rain. After determining its pH, they poured the solution through
cups that contained various earth materials (sand, potting soil
and crushed limestone). The students measured the amount of solution
that percolated (passed) through a hole in the bottom of each cup
in a set amount of time, and they tested the pH of the drippings.
The results of the group's experiment are shown in the following
table.
| Earth Materials |
pH of "acid rain" before percolation |
Amount of "acid rain" percolated in 3 minutes |
pH of percolated "acid rain" |
| sand |
3.0 |
30ml |
3.5 |
| potting soil |
3.0 |
20ml |
3.5 |
| crushed limestone |
3.0 |
90ml |
5.0 |
| all three Earth materials |
3.0 |
50ml |
5.5 |
Question 1 - Event Score = 0
What is one problem that this group is investigating? State the problem
in your own words.
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Score
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Commentary
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Question 1
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This response does not correctly identify one
of the problems being investigated. Serious misconceptions are
indicated ("vinegar being a fat does not stick to water" and
"the vinegar will stick to the rocks"). |
Question 2 - Event Score = 0
What are the variables that need to be controlled in this experiment?
Explain why it is important to control them.
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Score
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Commentary
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Question 2
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This response does not correctly identify any
of the important variables of the experiment. There is no justification
for why the cup should affect the results of the experiment.
There is no explanation as to why an experiment should be controlled.
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Question 3 - Event Score = 0
Do you have enough information to replicate this group's experiment?
If you think you do, tell what information you have. If you think
you do not, tell what other information you would need.
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Score
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Commentary
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Question 3
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This response not only fails to discuss the important
information that is provided, but also states that no other
information is needed. |
Question 4 - Event Score = 0
The group concluded that sand and potting soil have the same ability
to neutralize acidity because in each case the pH went from 3.0 to
3.5. Based on this group's experiment and results, do you think the
group's conclusion is valid? Explain why or why not.
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Score
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Commentary
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Question 4
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The response is incorrect. The explanation for
why the conclusion is valid is very poor. |
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