| Electricity
and Magnetism > Magnetic Materials |
DCS#
5G30.20 |
PARAMAGNETISM OF
LIQUID
OXYGEN
-
APPARATUS
| strong
magnet |
202-20-C |
| steel ball |
202-20-D5 |
| aluminum foil |
202-02-E1 |
| dewar |
101-01-B |
| liquid nitrogen |
Science Center dock |
| video camera |
202-09-D |
DESCRIPTION
- An aluminum foil cone is filled with
liquid
nitrogen. Liquid oxygen condenses on the sides of the cone and
drips
between the poles of the magnet where it sticks until it
evaporates.
Liquid nitrogen can be poured into the magnet gap to show that it is
not
paramagnetic.
- NOTES
- Place a steel ball bearing on
one of
the magnet
poles to reduce the size of the gap. Fold aluminum foil into a
cone
and fill with liquid nitrogen.
- Boiling temperature of liquid
oxygen
is -183°
C (90K).
- Boiling temperature of liquid
nitrogen is
-196° C (77K).
Molecular orbital theory shows that the triplet state of O2
(with outer shell electron spins parallel) has a lower energy than the
singlet state (with antiparallel spins forming part of a double
bond). So there are two unpaired electrons in molecular oxygen.
-
REFERENCES
Sutton,
H-11, E-102.
Freier and Anderson, Es-3.