60. Fun With LN2

In order to get liquid nitrogen we need a little extra notice. Some experiments are:

1. Flowers can be frozen brittle or fruit frozen solid so they will shatter when dropped. Another good demonstration is to bounce a racquetball and then use liquid nitrogen to freeze it and shatter it.
2. Balloons of air can be completely deflated and thrown on the floor to reinflate. If helium-filled balloons are used, their volume will be reduced to about one quarter. They are now denser than air and will drop to the floor, rising to the ceiling after a few minutes as they warm up.
3. You can plunge your hand into the liquid nitrogen for an instant. The Leidenfrost effect (vapor barrier) protects your hand.
4. A piece of the new high temperature superconductors will float a small magnet demonstrating the Meissner effect after cooling in LN₂. We also have a highly pinning superconductor which will float over a magnet track, or even under the magnet track
5. Liquid nitrogen can be shown to freeze when the air is pumped out of a glass chamber as depicted in the video below.
6. The temperature coefficient of resistance can be investigated with a copper wirewound resistor and a carbon resistor. A small circuit with a battery, lightbulb and resistor is set up and then the resistor is put into a cup of liquid nitrogen. The change light brightness indicates the sign of the temperature dependence. The temperature dependence of a semiconductor can be investigated by dipping a large green LED into liquid nitrogen and noting the color change.
7. Ice Cream Recipe