The substance oxygen has the following properties: normal melting point: 54.8 K normal boiling point: 90.2 K triple point: 1.50×10-3 atm, 54.4 K critical point: 49.8 atm, 154.6 K At temperatures above 154.6 K and pressures above 49.8 atm, O2 is a . O2 does not exist as a liquid at pressures below atm. O2 is a at 1.50×10-3 atm and 96.5 K. O2 is a at 13.2 atm and 48.1 K. O2 is a at 1.00 atm and 82.0 K.