What is the application of these gases?

Nitrogen: Used as coolant. Liquid nitrogen is used to cool things , also cool treatment in medical cases.

Carbon Dioxide: Used as fire extinguisher. CO2 is used to cut out the oxygen supply of the fire.

Hydrogen: Make butter, hydrogen is used to make liquid vegtable oil into solid butter at room tempareture.

Neon: It is a noble gas, and it is filled in glass tubes to make lights, you can see the street signs, that can change colour (they are neon light)

Argon: It is also an noble gas, it is filled into the light bulbs to prevent hot tungsten to react with air.

Helium: Used to fill the balloons , those that can float very high.

Oxygen: Reactant of repiration. (Breathing)