How are atmospheric pollutants formed?

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Chemical reactions happen when is burnt in air. The air consists mainly of and oxygen. The fuel is a mixture of which are compounds of carbon and hydrogen. The products of the combustion process are carbon dioxide, nitrogen, carbon , nitrogen , and . Most of the nitrogen passes through the engine without change.

In the petrol engine the liquid fuel vaporises. This is then mixed with air. The reaction between the fuel and oxygen is started by a . This explosive reaction releases a lot of . The force of the explosion drives the moving parts of the engine. New chemicals are formed during this process. This happens because the of the fuel and air are broken, and the free atoms join with other atoms to make new compounds. All the atoms at the start of the chemical reaction are still there after the process. However, many will have different partner atoms, as new compounds are formed.

Vehicles which are more than three years old in the uk require a test. During this test the quantities of pollutants from the are measured. If the cocentrations are too high, the car will the test. In order to reduce the amount of pollutants entering the air many cars use convertors. The waste gases from the combustion process are made to pass through a honeycomb structure. This structure has a very large surface . A metal coating, such as platinum, acts as a , to speed up the reactions between the waste gases. This enables less harmful chemicals to be formed. This reduces the concentration of carbon and nitrogen entering the atmosphere. However, the amount of carbon is increased.