Shown above is a mixture of liquid O2 and O3 (ozone). O3 condenses to a dark blue fluid (bottom layer) at −112 °C, and O2 to a lighter blue liquid at −183 °C. Both liquids are powerful oxidizers. Liquid O2 has applications in aerospace propellants and explosives, but liquid O3 is less useful because it can easily detonate when it reaches its boiling point. On an open lab bench, a flask like this is a safety hazard.
In the triplet form, O2 molecules are paramagnetic. That is, they impart magnetic character to oxygen when it is in the presence of a magnetic field, because of the spin magnetic moments of the unpaired electrons in the molecule, and the negative exchange energy between neighboring O2molecules.
Liquid oxygen is attracted to a magnet to a sufficient extent that, in laboratory demonstrations, a bridge of liquid oxygen may be supported against its own weight between the poles of a powerful magnet.