charles law using syringes

Discussion in 'Supporting Physics' started by mimi, Jun 14, 2019.

  1. I would like to try this experiment using syringe stops/caps as I couldnt get a seal using a bung or blu tac.
    Has anyone any advice on where to get the syringe caps from please?
  2. For Charles law we use the capillary tube method.

    We use silicon tube and Hoffman clips as in the aqa practical book to seal them for Boyle's law.


    or use a 3 way valve as in the setup guide

  3. Hi , I bought mine from Timstar a couple of years ago, they were called 3-way tap.
  4. Nick Mitchener

    Nick Mitchener COMMITTEE

    we have tried with gas syringes but they just leak too much. Will try making the sulphuric acid capillaries next.
  5. ours use this method


    no acid and ours are 5+ years old.
  7. Nick Mitchener

    Nick Mitchener COMMITTEE

    oh I like that. What oil did you use?
  8. Thanks Paul I had forgotten about 3 way taps!
  9. Thanks Paul , the mineral oil sounds preferable to sulfuric acid. will give it a go.
  10. I didn't make them, probably liquid paraffin though.
  11. I made some tubes like this. Used capilliary tubing, sealed the end in a bunsen flame and the bead is veg oil. The Physics teacher seems happy enough with them, used a few times for absolute zero. I think CLEAPSS has instructions somewhere.
  12. PhysicsSimon

    PhysicsSimon COMMITTEE

    Another option (still fine by CLEAPSS - well it was last time I looked) is to use a mercury bead
  13. I think the only advantage to the Suph acid is that it absorbs any water vapor in the tube.
    They are a PitA to get right though.
  14. Nick Mitchener

    Nick Mitchener COMMITTEE

    We spent a lot of time and effort getting mercury out of the labs, we are not about to bring it back!
  15. They are, we tried for many frustrating minutes - I'm sure there's a knack to it, but I can't remember what...
  16. karen b

    karen b COMMITTEE

    A very fine wire poked into the acid/mercury bead allows split threads to rejoin and you can usually adjust the position of the droplet as well.

    We use the mercury bead method given in cleapss.

    For the syringes I use thin walled rubber tubing folded over with a pinch clamp forming the seal. They are just standard plastic syringes and work tolerably well. Tying the string loop was the hardest bit
  17. what size beakers do you use for the capilliaries, we have 2L ones, i'm looking to downsize as one broke.
  18. karen b

    karen b COMMITTEE

    We have some tall 800ml weird shaped beakers (slightly conical) that we use. They are not really used for anything else
  19. They are called Philips beakers
  20. Tall form 400ml Beakers.
    As long as the air column stays below the water level everything should be fine.