science

Heat the liquified gases.
Different gases have different boiling point.

condensation

Cne of the methods of producing liquefied nitrogen is to compress air and shoot the mixture through an expansion nozzel. The Joule-Thompson cooling that occurrs when the gasses are expanded isbelow the condensation temperature of nitrogen but not above that of oxygen. The liquefied nitrogen is then collected in a condensation trap and bottled.

In intustrial situations the vapor (oxygen) is then further cooled to produce liquefied oxygen.

Rap