the earth's atmosphere
The gases that make up the earth's atmosphere:
- Nitrogen (N2) 78%
- Oxygen (O2) 21%
- Argon (Ar) 1%
- Carbon dioxide (CO2) 0.04%
- Water (H2O) 0-4% variable
Human activities add small amounts of chemicals to the atmosphere.
Some of these chemicals are harmful and are called air pollutants.
the earth's atmosphere continued
Power stations and vehicles that burn fossil fuels add:
- small amounts of the gases carbon monoxide, nitrogen oxides and sulpher dioxide to the atmosphere
- small amounts of very small particulates, such as carbon called particulates, to the atmosphere
- extra carbon dioxide that contributes to global warming
Primary pollutants are released directly into the atmosphere.
Secondary pollutants, such as nitrogen dioxide and acid rain are produced by chemical reactions in the atmosphere.
The fossil fuel coal is mainly carbon.
fuels and global warming
Fuels such as petrol, diesel and natural gas are hydrocarbons.
Hydrocarbons are chemicals made from carbon and hydrogen only.
When a fuel burns the oxygen atoms from the air combine with:
- Carbon atoms to form carbon dioxide.
- Hydrogen atoms to produce water.
In a chemical change/reaction atoms seperate and recombine to form different chemicals.
Chemical changes can be shown by pictures of the atoms and molecules involved.
During a chemical change, the number of atoms of each kind is the same in the products as in the reactants.
The consevation of atoms means that combustions reactions affect air quality.
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The properties of the reactants and products of chemical changes are different.
Technological developments such as catalytic converters and flue gas desulphurization can reduce the amounts of pollutants released into the atmosphere.