C7

• Hydrocarbon is any compound that is formed from carbon and hydrogen atoms only
• Alkanes have all C-C single bonds
• General formula is Cn H2n+2
• Alkanes are a homologous series - a group of organic compounds that react in a similar way
• Alkanes are saturated compounds - each carbon atoms has four single covalent bond
• First 4 alkanes are methane, ethane, propane and butane
• CH4 is formula for methane, a colourless gas at room temperature and pressure
• C2H6 is the formula for ethane, a colourless gas at room temperature
• C3H8 is the formula for propane, a colourless gas at room temperature
• C4H10 is the formula for butane
• Hydrocarbon properties change as the chain gets longer
• The shorter carbon chains the more runny the hydrocarbon
• Viscousity is how runny or thick something is
• less viscous-gloopy
• Shorter the carbon chain the more volatile and more flammable
• More volatile means it turns into gas at a lower temp and vapourises o condenses more easily
• Properties of hydrocarbons affect how they're used for fuels
• Complete combustion occurs when there's plenty of oxygen
• Incomplete combustion occurs when not enough oxygen so less energy released, produces CO and H2 which are toxic to humans
• Complete combustion of any hydrocarbon in oxygen releases lots of energy and produces carbon dioxide and water as waste products
• hydrocarbon + oxygen - carbon dioxide + water (+energy)
• Oxidation can be defined as the gain of oxygen
• Crude oil is made over a long term period of time from the remains of plants and animals that died millions of years ago and were buried in mud
• Under high temperature and pressure the remains turn into crude oil which can be drilled up from rocks
• Fractional distillation is used to separate hydrocarbon fractions
• Crude oil is a mixture of lots of different hydrocarbons, most of which are alkanes
• LPG stands for liquified petroleum gas
• Fractional column is very hot at the bottom and cool at the top, so the water is heated by the hot water at the bottom and cooled by the cool water at the top
• Heavy fuel oil is at the bottom of the column
• LPG is at the top of the column
• Longer hydrocarbons have higher boiling points
• Cracking means splitting up long chain hydrocarbons into shorter hydrocarbons
• Short chain hydrocarbons are flammable so make good fuels that are in high demand
• Long hydrocarbons aren't as in demand as much
• Cracking also produces alkenes
• Cracking is a thermal decomposition reaction
• CATALYTIC CRACKING

  Vapourise long chain hydrocarbons, the vapour is then passed over a hot powdered aluminium oxide catalyst, long chain molecules split apart on surface of specks of catalyst
• STEAM CRACKING

  Vapourise them, mix with steam then heat to very high temperature
• Formula for alkenes = Cn H2n
• Alkenes have a double c=c bond