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Soiled Again
Examples of Student Work
Contributed by: Connecticut Academic Performance Test (CAPT)


There is one example for each score point ranging from 3 down to 0. Explanations of the scores were written by staff from the Division of Teaching and Learning at the Connecticut State Department of Education who conducted training and scoring of field tested events.




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 = 3

What is one problem that this group is investigating? State the problem in your own words.



Component
Score
Commentary
Question 1
(3)
This response correctly states both problems that are being investigated. In each case the independent variable ("earth materials") and dependent variables ("acidity of acid rain as it is filtered through" and "how long the acid rain solution takes to seep through") are correctly identified.



Question 2 - Event Score = 3

What are the variables that need to be controlled in this experiment? Explain why it is important to control them.





Component
Score
Commentary
Question 2
(3)
The response discusses several variables that are important to control ("amount of water and material" and "amount of time"). The importance of controlling these variables is discussed.





Question 3 - Event Score = 3

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.




Component
Score
Commentary
Question 3
(3)
This response is correct and elaborate. It identifies several pieces of information that are needed to replicate the experiment ("how much earth materials", "how much acid rain" and, "What ratio the water and vinegar were in").



Question 4 - Event Score = 3

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.





Component
Score
Commentary
Question 4
(3)
The response is correct. It correctly explains that the results can not be validly compared because of the different amounts of acid rain percolated. The explanation is elaborated.


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