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Introduction: 

    We decided to use liquid oxygen because of a desire to capture the image of an original splash by affecting it with a magnetic field.  Liquid oxygen is one of the few substances that, when in liquid form, has magnetic properties.  However, liquid oxygen can only be present at extremely low temperatures and/or at extremely high pressures.  The condensation point for liquid oxygen at a pressure of 1 atm is -183°C¹.  Because of this we used liquid nitrogen to cool oxygen gas to this low temperature so that it would condense.  Since the boiling point of liquid nitrogen is -208°C², and, like all other substances, liquid nitrogen will remain at boiling point until completely evaporated, it was not difficult to get the O₂ to condense.

    The most important property of liquid oxygen for our original project’s goal is its paramagnetism.  Paramagnetism, or the tendency of a molecule to be attracted by a magnetic field, occurs when unpaired electrons are present in the electron configuration.  Substances that are paramagnetic can be affected by a magnetic field, but do not remain magnetic on their own (i.e. two paramagnetic substances would have no effect on each other).  Liquid oxygen’s paramagnetism is caused by the pair of unpaired electrons present in one of the pi bonds, specifically the anti-bonding 2p pi bond³.  Interestingly, the valence-shell electron-pair repulsion (VSEPR) theory does not predict these unpaired electrons, but the more sophisticated molecular orbital (MO) theory does.

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