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Homework Help: Which Does A Better Job of Rinsing Out A Glass

  1. Sep 20, 2009 #1
    When it comes to washing glasses, there is always a little residue left over. Presume for a 100mL glass about 0.50mL is left behind when you pour out the contents. Which will do a better job of rinsing out the glass after the first pour? Rinsing 1 time with 1.000L of water (in a large out container like a sink) or rinsing 3 times with 50mL of water? Show why.

    I think it would be rinsing 3 times with 50mL of water. If you only rinse it once with the 1L of water, it is kind of hit or miss. Either you get it all or you don't, but with the 3 separate rinsings you are more likely to get it all or at the very least dilute it enough to prevent the left over contents of the glass from corrupting your data. As for showing why, i was thinking of showing a dilution series for the glass as the 50ml of water is added each time. Does that seem correct? Any suggestions or corrections to my logic are greatly appreciated.
  2. jcsd
  3. Sep 20, 2009 #2


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    Staff: Mentor

    Yes - three times is better. No - it is not hit and miss.

    Think this way: there is a thin film of water left on teh glass surface after rinsing. What you do is you dilute it with each rinsing.

  4. Sep 20, 2009 #3


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    Homework Helper
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    Try to examine this at a very low level, and perform a mathematical simulation. Compare the results between the two methods.
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