GCSE chemistry unit 1 - fractional distilation of air

Fractional distillation of the air

Today the air is a mixture of:

• 78% nitrogen
• 21% oxygen
• And 1% other gases (including 0.04% carbon dioxide and 0.8% argon - a noble gas)

Fractional distillation

The air is cooled to -200 degrees so all the gases in the air are condensed into a liquid. Carbon dioxide and water are then removed so we are left with the other gases including nitrogen, argon and oxygen, which all have different boiling points. Heating it to a hoc her temperature each time, nitrogen evaporates first, then argon, then oxygen which can be collected as three different substances.

Uses of argon

• Unreactive so used inside filament bulb and fluorescent tubes
• Preserving old document because they are so unreactive.

Uses of nitrogen

• Food packaging to stop food decomposing (unreactive)
• In liquid form it can preserve living cells
• Fertilisers

Uses of oxygen

• Part of fuels for rockets
• Oxygen masks etc.