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Identifying and Controlling Variables
Worksheet
Grade Level
Grade 7
7.3 Identifying and Controlling Variables
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A class wants to test whether the concentration of a cleaning solution affects how quickly it removes a marker stain from plastic. Which setup best isolates concentration and keeps the test fair?
A
Use different sizes of stains for different concentrations.
B
Make identical marker stains on equal-size plastic squares, apply equal volumes of 25%, 50%, 75%, and 100% solution for the same time, scrub each square with the same pressure and number of strokes, and rate remaining stain using the same chart; repeat trials.
C
Scrub longer for low concentration and shorter for high concentration.
D
Use different brands of cleaner for different concentrations.
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