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 LESSON 2.  Investigating A Problem  (Lab) PROBLEM:  How can you determine the best paper towel for your money? Before lab:  Bring different types of towels from home… ask parent for price, rolls, # in each one ply or two ply  HYPOTHESIS: MATERIALS: Various paper towels, 2 lb coffee can, 400ml beaker with water, clear plastic cup (8 oz), triple beam balance, rubber band, mass weights, ruler, and calculator  PROCEDURE: Record the mass of the dry towel and cup.  Wet the towel for 10 seconds and remove let drip for 10 seconds place in cup and measure mass.  Subtract the dry mass from the wet mass to determine the water absorbed. Place the wet towel on the top of the coffee can and secure with a rubber band.  Carefully stack weights in the center of the towel, adding a new weight every 5 seconds, in a single stack.
 Brand wt of mass held on wet towel Mass Towel +  Cup dry Mass towel +  cup wet water absorbed
 Record the cost of the roll and the number of towels per roll.  Divide the cost per roll by the number of towels per roll and you will get the cost per towel.  Now imagine a 200ml spill.  Using the amount of water absorbed by the towel in the above chart determine the number of towels that will be needed to pick all of it up.  (1gram of water = 1ml of water) Multiply the number of towels per spill by cost/towel and record your cost per use.
 Brand cost /roll # towels/roll cost/ towel 200 ml spill cleanup cost per use
 CONCLUSION:  What is the best brand of paper towel?

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