Topic

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.

Description

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     and nitrogen.
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.

Apparatus

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.

Wooden spills.

Rubber tubing.

Two pyrex test-tubes 12 x 150mm.