Chemicals

About 1.5 dm of liquid nitrogen will be enough to do all of the demonstrations described.
Lead sheeting, about 1-2 mm thick.
A few cm of mercury.
Access to an oxygen cylinder and regulator.
Access to a hydrogen cylinder and regulator.
Access to a carbon dioxide cylinder with regulator.
A little washing up liquid and some food dye (optional).
Bubble mixture.
One banana and/or flower.



Method

1. Pour some liquid nitrogen into an expanded polystyrene box and immerse a variety of items into it.

(a) Mercury (in a small test-tube) solidifies.

(b) Rubber or plastic tubing goes brittle and can be snapped in gloved hands or shattered with a sharp blow.
(c) A strip of lead becomes rigid and will 'ring' when tapped with another metal.
(d) A banana, for example, will become brittle and will shatter if it is hit on the bench. Take care to clear up all the shattered pieces - they become very soggy on melting!
(e) Flowers or leaves will become brittle.
(f) A ballon blown up with air (by mouth) will shrink as the air liquefies. Liquid air can be seen and felt inside the balloon. The rubber attains a texture rather like a crisp packet. The change is fully reversible. A balloon blown up from a hydrogen cylinder shrinks to about 1/3 of its original size because in this case the gas will not liquefy. The balloon expands back to its original size when it is removed. If a suitably sized balloon is used, the balloon will sink to the floow when shrunken and will float as it warms up and expands. These are dramatic examples of the gas laws and deviations from them.
(g) A soap bubble can be held on a wire 'wand' over a container of liquid nitrogen. It will freeze.