The atmosphere is a mixture of gases: The atmosphere is mostly made up of: Nitrogen(78%), Oxygen(21%) Argon(1%) and other gases.
The concentrations of Oxygen, Nitrogen and Argon in the atmosphere are pretty much constant but human activities adding small amounts pollutants in the air.There are 5 pollutants you need to know about: Carbon dioxide, Carbon monoxide, particles of carbon, sulfur dioxide and nitrogen oxides.
The pollutants above come from many different sources e.g. vehicles burn fuels and power stations. They can cause disease or death in people who inhale large enough quantities. Pollutants can also harm us indirectly by damaging our environment e.g acid rain which acidifies e.g lakes.
Hydrocarbon:Is a compound containing 2 elements(Hydrogen and Carbon atoms only.) Fuels such as petrol , diesel and fuel oil are mixtues of carbon and hydrogen atoms only. Many power stations also burn hydrocarbons e.g. natrual gas. Many other stations burn coal. Coal isn't a hydrocarbon-it's just Carbon(with a few impurities.)
Chemistry(Chemical synthesis and polymerisation)
crude oil is formed from the buried remains of plants and animals-it is a fossil fuel .over milliions of years, with hight temperature and pressure the remains turned into crude oil which can be drilled up
crude oil is a mixture of lots of substances. crude oil is a mixture of hydrocarbons -molecules which are made of chains of hydrogen and carbon atoms only. these chains vary in length