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Thread: Relative size of water, IKI, starch, and glucose molecules

  1. #1 Relative size of water, IKI, starch, and glucose molecules 
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    Dec 2009
    Hi there! I'm doing a small lab report for a biology lab we did in class last week. The lab was essentially teaching us about dialysis and osmosis. We had 6 known concentrations of a glucose solution. We put 10mL of each solution in a separate membrane tubing and immersed them separately in a glucose solution of an unknown concentration. We massed the bags before and after being immersed to figure out how much the massed changed. Based on this data, we were supposed to discern what the unknown concentration of the glucose solution in the beaker was.

    There is a question on the lab that asks us to list, from smallest to largest, the relative size of water molecules, glucose molecules, starch molecules, IKI molecules, and membrane pores based on our results.

    I came up with this order: water molecules, IKI molecules, membrane pores, glucose molecules, starch molecules.

    I can explain my answer for the most part, but I'm having trouble telling whether or not water molecules are larger than IKI molecules. I figured that since water is made up of hydrogen and oxygen atoms, which are relatively small, and IKI is made up of iodine and potassium-iodide is made up of potassium and iodine, which are larger atoms (I think...), that IKI molecules would be larger than water molecules. Is this a fair assumption? I'd appreciate if anyone would assure me that I am on the right path. Any help is very much appreciated. Thank you!

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