1. The Atmosphere The atmosphere is made up of a mixture of gases which are small molecules with large spaces between them. The main gases are: Nitrogen 78% Oxygen 21% Argon 1% Small amounts of other gases e.g. carbon dioxide (0.037%) and water vapor 2. Evolution of the Atmosphere The early atmosphere would have been made of mainly carbon dioxide and water vapor released by volcanic eruptions and volcanic activity. As the earth cooled the water vapor condensed and formed the oceans. The evolution of photosynthesizing organisms caused the production of oxygen and the reduction of carbon dioxide. Carbon dioxide also dissolved in the oceans, which was used by organisms in the sea to create their shells. These shells were converted into sedimentary rock over millions of years and eventually turned into fossil fuels. These processes produced the atmosphere as we know it today. 3. Air Pollutants The major air pollutants are: Pollutant Formula Particle diagram Produced by Problem Carbon dioxide CO2 The combustion of coal and fuels (i.e. hydrocarbons) Causes global warming Carbon monoxide CO Incomplete combustion of coal and fuels Poisonous to humans by stopping the red blood cells carrying oxygen Carbon particulates C Incomplete combustion of coals and fuels Linked to asthma and global dimming. Cover buildings with soot Sulfur dioxide SO­2 Combustion of coal and fuel containing impurities of sulfur Causes acid rain by dissolving in rain clouds Nitrogen dioxide NO2 Combustion of nitrogen in car engines produces nitrogen monoxide which is oxidized in the atmosphere to form nitrogen dioxide. Causes acid rain by dissolving in rain clouds 4. Combustion of Coal Coal is made up mainly of carbon. Coal is often burnt in power stations and the energy given off is used to make electricity. When coal burns (combusts) it reacts with oxygen in the air to produce carbon dioxide. The chemical equation for this is: Carbon+Oxygen = Carbon dioxide The