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chemistry paper 2 (using reasources (water reasources (their are many…

- - - - these types of water source can be purified by filtering and then being treated by chlorine or uv light
- - - - around 2.7 billion years ago plants and algea began to form removing carbon dioxide to be removed a billion years ago this had led to enough oxygen for animals to evolve
  - - - layers of sedimentary rock build up on top
        
        the heat and pressure from these rocks along with the absence of oxygen mean that oil and gass are formed
  - - - however a layer of gasses around the earth cause the heat to reflect back to earth
- - - - most hydrocarbons in crude oil are alkanes which form a homologous series and only have single carbon-carbon bonds like ethane and butane
        
        alkanes have different properties depending on their length a longer chains means that they are more viscose ,less flammable and have a higher boiling point
  - - - the oil is evaporated and the hydrocarbon chains condense at different temperatures
        
        fractions with low boiling points condense at the top for example petrol at 40 degrees were as fractions with high boiling points condense at the bottom for example residue which condenses at 340 degrees and is used for lubricating oil
        
        crude oils ability to form different compounds makes it able to form fuels and feedstocks such as solvents
  - - - shorter chai molecules are in higher demand than those with longer chains as they burn easier
      - shorter chain molecules can be created by cracking longer chain molecules
      - catalytic cracking
      - steam cracking:the alkanes are heated then vaporised at very high temperatures and then diluated with steam they are the reheated for a short amount of time.