In this BOC liquid nitrogen episode, we will be looking at thermal contraction.
In this video there is a metal ring and ball. At ambient temperature, the ball easily fits through the ring. When the ring is submerged in liquid nitrogen, a process called thermal contraction takes place. As the molecules inside the metal ring are rapidly cooled, they lose energy, slow down and the distance between them reduces, causing the metal ring to contract.
After the ring is removed from the liquid nitrogen, something pretty interesting happens – the ball no longer fits through the hole!
If you wait long enough, the metal ring will warm back up to ambient temperature. The molecules will gain more energy, increase speed and the distance between them will get bigger. This will cause the metal ring to expand again, allowing the ball to fall through. This process is called thermal expansion.
Safety Notice
When using liquid nitrogen always remember to:
-Refer to the Safety Data Sheet beforehand. These are available at
www.boc.com.au and www.boc.co.nz
-Wear Personal Protective Equipment that at least meets the
requirements of the SDS
-Ensure the work area is adequately ventilated
-Ensure participants have undergone adequate training
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