• Question: how is liquid nitrogen made

    Asked by 676cars46 on 23 Sep 2016.
    • Photo: Ian Hands-Portman

      Ian Hands-Portman answered on 23 Sep 2016:

      We use about a hundred litres of liquid nitrogen in the lab every week! We don’t make it ourselves – it’s delivered by tanker. Making liquid nitrogen relies on the way that gasses get hot when they’re compressed and cool when they expand.
      Nitrogen gas from the air ( which is 78% nitrogen ) is compressed in – which makes it heat up, then it’s allowed to cool back down again. Once it’s back to normal temperature, quickly releasing the pressure – the temperature drop so much that it condenses into a liquid. It’s the same basic way that fridges cool things down and aerosol cans get cool when you spray them.

    • Photo: Katie Mahon

      Katie Mahon answered on 23 Sep 2016:

      I definitely didn’t know the answer to this one! Thanks to the internet I can find out more 🙂 A big part of being an engineer or scientist is knowing how to research & learn more about new subjects! Don’t be afraid of not having the answers – just keep asking questions. Here’s an answer to yours:

      “Liquid nitrogen is made by cooling and compressing air straight from the atmosphere. Now there are lots of different types of air compressors for lots of different applications. One you may have seen is the type used by carpenters to power tools, such as nail guns. The type used to produce large amounts of liquid nitrogen looks vastly different but all it really does is squash and cool air. When you squash it, air molecules are forced closer together. If you also cool it down the molecules can slow down enough to make weak bonds. When enough molecules start bonding together like this, droplets of liquid form. This process is called condensation.”

      http://www.abc.net.au/science/surfingscientist/behind.htm

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