Alkanes

• Non-polar because the difference in electronegativity between C and H is very small. 
• Intermolecular force = VDW force, increases as the relative molecular mass increases. Resulting in an increase in melting/boiling point. 
• Branched chains = lower melting point due to smaller surface area.
• Insoluble in water, but will dissolve in non-polar liquids. 

Cracking: Where long chained molecules are broken into shorter molecules which are higher in demand. 

Thermal cracking:

• Long chains are exposed to higher temperatures of 1200K and 70atm for a short time(to prevent it turning to C and H)
• Produces shorter alkanes and some alkenes. 

Catalytic cracking:

• Heated to 1000K and 2atm with a catylist called zeolite, an acidic material with a honeycombe structure.
• Operated continuously to produce branched alkanes, cycloalkanes and aromatic compounds.
• Used to produce fuel for road vehicles.
• Temperatures and pressures need to be high as the C-C bonds are really strong. 

Complete: 

• methane + 2oxygen --> carbon dioxide + 2water.

Incomplete:

• methane + 1.5(limited)oxyden --> carbon monoxide + 2water
• methane + (very limited)oxygen --> carbon + 2water

Consequences:

Global warming - producing the greenhouse gases; water vapour and CO2.

Acid rain - Nitrogen oxides produced by high temperature combusion and sulphure dioxide produced when impurities in fuel is burned causes acid rain.

Photochemical smog - produced when nitrogen oxides, sulfur dioxide and unburnt hydrocarbon fuels react wit sunlight. Can also include carbon. Causes health problems from irritated eyes to lung disease.  

Catalytic converters:

• 2NO + 2CO ----> 2CO2 + N2

Removing Sulfur: 

• CaO + SO2 ---> CaSO3
• CaCO3 + SO2 ---> CaSO3 + CO2
• CaSO3 + [O] ---> CaSO4