Monday, 1 July 2013

recommended project

Time RequiredShort (2-5 days)


There are three different kinds of polymers used for kitchen plastic wrap: polyethylene (e.g., Handiwrap or Glad Wrap), polyvinyl chloride (e.g., Reynold's Plastic Wrap) and polyvinylidene chloride (e.g., Saran Wrap, which is almost 90% polyvinylidene chloride). Which of these materials is least permeable to oxygen? When you slice an apple, the surface of the slice turns brown as the apple is oxidized. Can plastic wrap seal out oxygen and prevent the apple from browning? Which plastic wrap works best? Do background research on the different polymer types used for plastic wraps in order to develop a hypothesis. Use samples of each type of plastic wrap to cover 9 apple slices (3 slices for each wrap). Cut the wraps with a scissors so you don't stretch the material. Prepare your materials in advance so that you can wrap each slice right after it is cut, since oxidation starts immediately. Keep 3 slices unwrapped as controls for comparison. Compare the slices at regular intervals and note your results. You may want to take pictures to use for your display board. Do you think you would get the same results at a different temperature? How about if the slices were on saucers covered with plastic wrap? Does stretching the plastic make any difference? Can you think of other ways you might test oxygen permeability of plastic wraps? (Goodstein, 2004, 65–69)

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