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    • #15391
      Profile photo of Andrew Normand

      Use a simple pump to weigh air. See if the buoyancy changes as you add air. Available from http://www.kneesnet.com/acatalog/Kneesnet_Online_Fizz_Keeper_Pump_Cap_664.html
      It also has its own website http://fizzkeeper.org/ 

      Look for cheaper versions in your local super market.

      You’ll also need
      1g resolution  scales and an empty pop bottle
    • #15392
      Profile photo of Andrew Normand

      This can show a difference with remarkably cheap scales. The fizz-keeper works well and is probably worth the investment over cheaper versions but they too will show that air has mass. As well as pumping it up you can also buy similar items that remove the air from wine bottles. By placing a semi-inflated balloon or marshmallows in a pop bottle and removing some of the air you can see the effects of air pressure imbalances. Marshmallows in a bell jar connected to a vacuum pump are also an interesting demonstration.
      Themes: Gases, forces

    • #15393
      Profile photo of Andrew Normand

      have to try this

      you can make a cheap homemade bottle valve from a cork and the valve from a old bicycle inner tube.

      bike shop gave me a handful of old ones when I asked (the longer thinner type are better)

      if you put a bit of vodka (rubbing alcohol works even better) pressurise the bottle a little bit and then pull the cork out you can make a cloud in a bottle


      it gives a strong enough seal to make a cheap water rocket aswell (idea nicked from bang goes the theory)


    • #15394
      Profile photo of Andrew Normand

      corks on sale in hardware shops for home brewers

      wonder what would happen if you breathed in a shot of vodka vapour

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