What is air made of?

You never need to think of breathing, your respiratory system does that automatically for you.  But do you ever think about the air that you breathe every minute of every day?  Air is not the same as oxygen although sometimes people mean oxygen when they say air.  Your body takes the oxygen it needs from the air and your red blood cells transport it from the alveoli in your lungs to all the cells in your body.  Your body gets rid of the other gases in the air – but what are these?

Air is made up of two main gases – oxygen and nitrogen.  Even though you breathe oxygen, this is only 21% of the air, nitrogen makes up 78%!  The rest of the air, about 1%, is made up of other gases like carbon dioxide, methane, helium and a couple of other gases.  That’s not all – there are lots of very tiny particles suspended in the air you breathe – dust, microbes, spores from plants and water!

Water stays in the air as moisture – you can feel it when the weather is humid, it feels like the air is wet when there is no rain!  Some parts of the earth have more moisture in the air than others and the amount of moisture can change as the earth is heated by the sun during the day and it cools down at night.  For example, if you are in a desert, the air can be very dry but if you are in a swamp in a hot climate, the air can have a lot of moisture and feel very uncomfortable.  One of the big problems in humid weather is that when you sweat, it cannot evaporate to cool you down - there is too much moisture in the air already!

Everyone knows that humans can’t breathe under water but what about fish?  If you look closely at fish swimming, you will see little bubbles rises to the surface of the water.  The fish is breathing and it is breathing oxygen!  But, you know that if a fish is taken out of water, it will suffocate because it cannot take in enough oxygen from the air.  Fish had adapted so that they can take the oxygen they need to breathe through their gills.  Oxygen, dissolved in the water, is taken in through the fish’s gills, concentrated and picked up by the blood.  The blood flows in the opposite direction to the water flowing over the gills to make sure the most oxygen possible is picked up by the gills.  The blood carries the oxygen around the fish’s body where it is used by the fish’s cells. 

The oxygen in the air that surrounds the earth isn’t equal – for example, there is less oxygen in the air at the top of high mountains.  The higher you move up from the ground (this is called altitude), the ‘thinner’ the air becomes.  The pressure in the air is less the higher up you go and so, there is less oxygen.  Mountain climbers, who climb the very tallest mountains like Mt. Everest, need to bring canisters of oxygen with them because there is very little in the air by the time they get to the top.  A lot of mountaineers try to climb very high mountains without oxygen but they sometimes get ‘altitude sickness’.  This can be very dangerous and cause loss of sight, swelling of the body and brain or blood clots in the lungs or brain, all of which are very serious.  So why does this not happen when you take a flight?  Modern aeroplanes travel at very great heights, higher than most mountains, but the air inside the aeroplane is pressurised.  The air is artificially brought to a pressure when there is enough oxygen in the air for people to breathe comfortably.  You can feel this when you fly as your ears may pop when you are taking off or landing.  Remember to swallow or yawn lots to make sure the air pressure outside your ears is the same as the air pressure inside your ears or they may hurt!

The air you breathe is a very precious thing.  We all need to work very hard to make sure that we don’t pollute the air so much that it is damaging to our health.  Remember to do your bit – conserve energy, recycle and look after your environment!

Did you know…?

Whales and dolphins live in the sea, but they are mammals, not big fish?  They can hold their breath for a very long time but they do need to come to the surface to breathe!