Oxygen is a nonmetallic gas with atomic number of 8 in the periodic table.  The nonmetallic element is represented chemically with symbol O. You cannot taste, smell, touch or see the nonmetallic gas; however, that does not take way your ability to understand the importance of the gas in the human, nay, animal life. Moreover,

There is only one method for isolating oxygen from liquid air which is known as cryogenic distillation.  There are numerous techniques available for separating oxygen from the atmospheric air such as pressure swing adsorption (PSA) or membrane separation. However, these techniques do not do separation by liquefaction. Cryogenic distillation is the only process that works