The Air We Breathe

Year Seven
A description of each gas in the air, its percentage composition, and its industrial uses.


Nitrogen (N2)


Nitrogen is a colourless gas that makes up 78% of the earth's atmosphere. Nitrogen has many industrial uses as either an inert gas, liquid form (boiling point: -195.8C), or as ammonia. These include the preservation of food, a filler gas for light bulbs and (as liquid) a coolant for large computer systems. Also, when used to make ammonia, it can be used as plant fertilizer or disinfectant.


Oxygen (O2)


Oxygen is an odourless, colourless gas which makes up 21% of the air which we breathe. though it is usually found as a gas, oxygen sometimes exists in liquid form (boiling at -182.95C), where it can be used either as coolant, or combined with Hydrogen to make rocket fuel. When it is in gas form, oxygen can also play a role in sewage treatment (it increases the ability of cleaning bacteria in water), or burned at high temperatures. Welding torches burn oxygen with acetylene of Hydrogen to produce their effects and metal industries use burning oxygen to remove impurities from iron and steel. Oxygen is also, of course, rather essential to life, as all animal life forms need oxygen to survive (especially people with breathing problems, who are fed pure oxygen through a respirator.).


Argon (Ar)


Argon is a colourless gas which makes up less than 1% of the atmosphere. Argon can exist as liquid, though it boils at -185.85C, so it usually appears in gas form. Argon is often used as a filler gas, appearing in light bulbs (though now being replaced by Nitrogen), double glazing (between the glass panes) and museum display cabinets (to preserve delicate artefacts). Argon is also found in aerosol cans to preserve the contents.


Carbon Dioxide (CO2)


Carbon Dioxide is a colourless gas that makes up 0.038% of the air we breathe in. Liquid CO2 is very rare as Carbon Dioxide usually sublimes straight from solid to gas and vice versa. Liquid Carbon does exist however, and boils at -157C. Carbon Dioxide has several industrial uses, these include: Life jacket inflation, dry ice and refrigeration (in liquid form). Carbon Dioxide is also contained in yeast, which makes soft drinks fizzy and causes dough to rise.


Water Vapour/Steam (H2O)


Water vapour is a colourless (though it sometimes appears as white clouds) odourless gas in the earth's atmosphere. The actual amount of water vapour in the air varies depending on the humidity of the atmosphere. Warm, humid air can contain up to 3% water vapour, whereas cold, dry air will contain less than 1. Unlike the other gases in the air, water commonly exists as all three states of matter as, unlike the others, the boiling point of water is 100C rather than sub-zero temperatures, and its freezing point is 0.01C. Water vapour has several important uses in the industrial world. Chief among these is the power plant; with the exceptions of wind farms and solar cells, all power stations use water vapour to generate their electricity. By means of coal, oil, gas, uranium or reflected sunlight, water in huge boilers is heated up to evaporate and produce steam, which is then used to drive turbines which turn the generators to produce electricity. Water vapour is also used in steam cleaners, household a way of killing bed-bugs and, of course, old fashioned trains.


Originally written January 2010 by Robin Taylor. Scored at A.