What air is made of
Air is a mixture of several different gases
The most plentiful gas in air is nitrogen and most of the rest is oxygen
The composition of air |
Nitrogen: 78% Oxygen: 21% Argon: 1% Tiny amounts of carbon dioxide, helium and other gases (See table) |
How to show that air has weight
 BEFORE |
 AFTER |
A metre rule is balanced at its centre and an inflated balloon is hung from each end (see diagram labelled BEFORE)
When air is let out of one of the balloons we see the ruler move so that the side with the inflated balloon goes down.
This happens because the inflated balloon is heavier than the empty balloon showing is that air must have weight
The weight of air in an average room will be about 100kg!
Table showing the names of the main gases in the air and what they are used for
|
Name of gas |
Amount |
Uses |
|
Nitrogen |
78%
|
Nitrogen is the main gas in air. Nitrogen is used to make plant food (fertilizer) and is also in explosives.
|
|
Oxygen |
21%
|
Without oxygen we cannot breath and fires wont burn. Oxygen is used in hospitals to help us breathe. It also used in welding and as rocket fuel. Oxygen is produced by plants (during photosynthesis). |
|
Argon |
1%
|
Argon is the gas inside electric light bulbs |
|
Carbon dioxide |
0.03% |
Carbon dioxide is the gas in fizzy drinks. It is also used in fire extinguishers. All living organisms breath out carbon dioxide when they make energy (from food). Carbon dioxide is needed by plants when they make food (during photosynthesis). Carbon dioxide is produced when wood, coal and other fossil fuels burn. |
|
Helium |
<0.01%
|
It is a very light gas and is used in balloons to help them float
|
|
Water vapour |
Varies |
Water vapour is formed when water evaporates. When water vapour in the air cools down it forms clouds. There is lots of water vapour in the air we breathe out.
|
|
Sulphur dioxide, soot, and other Pollutants |
Varies |
Sulphur dioxide is a gas produced by burning coal and other fossil fuels. It dissolves in rainwater to form acid rain. |
To find out more about air pollution click here.
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