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Edexcel 360 IAA - Duckweed experiments - help please.

Discussion in 'Science' started by anjminniemouse, Jun 6, 2011.

  1. hi, are you a technician? just asking because science technicians can make most things work! i think you are absolutely spot on both of these pracs are ' vague ' at the very least. In the past it has been known ( not by me you understand ;) ) to use cress individual leaves instead of duck weed to give an appropriate result after a week! but <u>really</u> if the results are a bit haywire its all down to life being life and can be explained in the students results as long as it was a fair test.Duck weed never has a problem in my pond plus Baby bio needs to be really dilute.
    Get some more advice on sci-tech forum, they are happy to help.
  2. The sugar testing one is vague, but it is very simple to deliver and surprisingly enough it works!
    5 bottles of lemonade with different amounts of red food colouring. They have to say before tasting which is the sweetest then after tasting. Almost all of them think that the more intense the colour the sweeter it is even after they have tasted it. I set up the cups and make a big fuss about all of the conditions being the same temp etc.
  3. ScienceAndPlants

    ScienceAndPlants New commenter

    I wasn't quite sure where the problems with the duckweed are coming up - is it related to growing the duckweed? The SAPS site has this tip on growing it, which you might not have seen:

    "Lemna minor grows best at a fairly low nutrient level. It does not compete well with algal blooms.

    I suggest boiling one wheat grain in a little distilled
    water and then make up to a litre volume. Put the
    duckweed on top. They should double every three days at
    22&ordm;C. I have read that sycamore / maple leaves are also a
    good nutrient source.

    pH 6-8 is OK, not outside that."

  4. sadscientist

    sadscientist Senior commenter

    Thank you AJF71 - I'll have to do this one next year so all advice very welcome.

    I can see this works well as a way of doing something to try to meet the IAA requirement. I still can't see how I can give them marks in the IAA for planning - when I've planned it - they're just the subjects. I think it's much too vague about validity/reliability/independent and dependent variables - i.e. the things we're supposed to be assessing. Just not scientific enough!
  5. sadscientist

    sadscientist Senior commenter

    Thanks for this, very helpful - the "life being life" factor does complicate things!
  6. I am going to trying this tomorrow. Thanks
  7. Excellent posting.

    Can you share any further information on the Edexcel 360 Science sugar in lemonade IAA?

    I am about to carry it out on a class of adults at an evening GCSE class.



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