An alternative to the Potassium manganate diffusion prac' please.

Discussion in 'Science Technicians - General Discussion' started by Julie Delaney, Dec 3, 2019.

  1. Julie Delaney

    Julie Delaney COMMITTEE

    I need an easy alternative to the potassium manganate diffusion practical as we have 2 pregnant ladies in the department and this one is now classified as possibly causing harm to the unborn child; we don't want to take any chances. I don't really want to go down the starch/ iodine visking tubing one if possible. any ideas?
    Thanks as always folks. :):):cool:
     
  2. Substitute the Permanganate with Phenolpthalein. You're right not to take chanes.:);)
     
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  3. Julie Delaney

    Julie Delaney COMMITTEE

    we don't have the solid, we only buy ready made liquid, we would have to use a slightly alkaline liquid though? surely?
     
  4. Yes Julie just over pH 8.2 (can be achieved by adding Sodium Carbonate or a Buffer, say pH 9.0)
     
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  5. Julie Delaney

    Julie Delaney COMMITTEE

    Thank you George. :):D:cool:
     
  6. Would food colouring added to both hot and cold water do it?
     
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  7. You can also show diffusion by putting a tea-bag in hot water, in a beaker. The colour shows up quite well, for the students to be able to see it moving through the water.
     
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  9. We use a deodorant/perfume spray - squirt in the front of the class and get the pupils to raise their hands when they smell it!
     
  10. Peter Sigsworth and Emil Retaw like this.
  11. That's a beautiful practical. We did this before. You can also do it with other salts that give insoluble precipitates. It not only demonstrates diffusion, but also shows that heavier ions diffuse slower which is something you don't get from the typical manganate practical.
     
    David Sait likes this.
  12. I take it you just put a crystal in the corner of a cold beaker of water and another in a hot beaker of water (as per year 11 exploring science) and watch - in which case phenolpthalein wouldn't work - some solid food colouring instead of the permanganate - can get powdered form easily. But even if you can't get solid and have only liquid can use and syringe to place a few undiluted drops in the corner of the beaker.
    If it's the diffusion in agar cubes then phenolphthalein is the recommended method.
     
  13. David Sait likes this.
  14. we use Marmite or Bovril ( love it or hate it ! ) , 1 spatula full in a beaker add hot or cold water and time how long it takes to dissolve.
    Leave the spatula in the beaker as it is very sticky and hard to get off !
     
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  15. Julie Delaney

    Julie Delaney COMMITTEE

    I would probably nick it for my toast!!:eek::D:D:D
     
  16. Julie Delaney

    Julie Delaney COMMITTEE

    that's a great practical, but, again, not for our pregnant ladies as the lead salts may cause harm to the unborn child; also it's for our year 7 and 8's so not suitable for the youngsters. Much appreciated though! :cool::D
     
    David Sait likes this.
  17. Could you premake the permanganate melts? so they are not handling the permanganate directly.
     
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  18. Also if you are doing it as a diffusion prac rather than convention we've done methylene blue ice cubes before which work really well.
     
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  19. We've just started to show diffusion for KS3 with a tea bag in different temperatures of water, or with skittles and hot water on a plate or petri dish
     
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  20. Tea bags in hot and cold water works very well
     
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