Liquid nitrogen demonstrations cover a
variety of topics. Institutions will usually only have occasional
access to liquid nitrogen and will probably wish to do all the liquid
nitrogen demonstrations at once. They could be done as part of a
lecture demonstration for interest and stimulation. The topics covered
include gas laws, liquefaction of gasses, fractional distillation,
combustion and bonding (the paramagnetism of oxygen).
The chapter on the properties of liquid oxygen
thus ties in with this chapter closely.
1. Various materials are immersed in liquid nitrogen
to demonstrate the effects of
low temperature on their physical properties.
2. Liquid air is made and distilled to show that it contains oxygen
3. Liquid oxygen is made and its colour, magnetism and ability to
support combustion are shown.
4. Solid carbon dioxide is made.
5. Liquid nitrogen is boiled and the gas used to inflate a balloon
and shown the volume increase.
One vacuum flask - about 1.5dm
is suitable. Ordinary household flasks
appear to be suitable. It is helpful if more than one flask is available.
Expanded polystyrene box such as those in which Winchester bottles
are sometimes supplied.
About 60 cm of copper tube as used for small-bore central heating
systems. This can be bent by hand.
Powerful permagnet such as an Eclipse Major.
2-3 cm of cotton thread or string.
Two party ballons.
Two pyrex test-tubes 12 x 150mm.