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    we've just started ocr a2 coursework and im already stuck, we're measuring oxygen levels with a manometre and using live meal worms!! is anyone out there doing the same!!!!
    or could anyoen tell em how to measure the volume of oxygen used up??
    also any recommendations for decetn revision books?
    thanks
    soph
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    (Original post by smessant)
    we've just started ocr a2 coursework and im already stuck, we're measuring oxygen levels with a manometre and using live meal worms!! is anyone out there doing the same!!!!
    or could anyoen tell em how to measure the volume of oxygen used up??
    also any recommendations for decetn revision books?
    thanks
    soph
    I believe you pass the air over the meal worms, then through limewater or bicarbonate to absorb the carbon dioxide. So the reduction in volume in the system is equal to the volume of oxygen used by the worms. As for measuring the amount used up you could have a capillary tube with a small marker of dye in it attached to the system. Then the movement of the dye along the capillary tube can be used to work out the volume of gas used.
    You have to make sure however that before starting the experiment there is no CO2 in the apparatus. I'm not sure how much these worms respire, but I think a 1mm2 capillary tube of 10cm or so should give a good duration of experiment from what I remember.

    As for revision books, I can't help there.
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    Theres quiet a good description of the experiment required in Essential A2 Biology for OCR (although this isnt a revision book)
 
 
 
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