Two Groups, Two Paper Towel Answers
Two fifth-grade groups investigated the question, 'Which paper towel absorbs the most water?' Group A used one full sheet of each towel, dipped it in a bowl of water for 10 seconds, let it drip for 10 seconds, and massed it on a balance. Group B cut each towel into 5 cm by 5 cm squares, used four squares stacked together, and counted the drops each stack held before water ran off. Group A reported gains of 22 g for Towel X, 26 g for Towel Y, and 19 g for Towel Z. Group B reported 38 drops for X, 31 for Y, and 44 for Z. Towel Y's group says their data prove Y absorbs most; Towel Z's group says their data prove Z does. The class must decide what to put on a bulletin board for the school.
1. Why do the two groups disagree, and which group's procedure better answers the original question? Explain using variables and units.
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The groups measured different things. Group A measured grams of water held by a whole sheet after a fixed drip time, which matches how a towel is actually used and uses a consistent unit, grams, that can be compared across towels. Group B measured drops held by small squares, which tests how much water sits inside the towel material but ignores sheet size and how the towel behaves while dripping. Drop counting also depends on the dropper, the tilt, and the moment a student decides a drop has run off, so the unit is not reliable. That explains why Y wins under Group A's method and Z wins under Group B's. Group A's approach better answers the question, provided each towel sheet is the same size.
2. What should the class standardize if they redo the investigation, and how should they report results on the bulletin board?
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Standardize the sheet size, the water source and temperature, the soak time, the drip time and angle, and the measuring method. Massing on the same balance is best because grams form a consistent unit and small differences show up. Run at least three trials per towel and report the mean for each, plus the range so readers can see how much the trials varied. On the bulletin board, show a bar graph titled with the method used, for example average grams of water held per full sheet after a 10 second drip, with the number of trials stated. Phrase the claim only as far as the data go, such as: under our test conditions, Towel Y held the most water.
3. Can the class now claim which towel absorbs the most? Explain what is missing and what it would take to make a trustworthy claim.
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No, because the two data sets disagree and neither group ran repeated trials. Group A tested one sheet per towel, so a single thick or thin sheet could decide the result. Group B measured drops, which is a less consistent unit and does not reflect whole-sheet performance. Before making a claim, the class needs one agreed procedure, repeated at least three times per towel, with results averaged and the spread reported. They also must define what 'absorbs most' means: water held per sheet, per gram of towel, or per dollar. A thick towel may hold more water but cost more. Reporting the method, the averages, and the variation is what separates a trustworthy claim from a lucky single trial.