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Chapter 21: Hydrocarbons and Crude Oil

21.1-Hydrocarbons

Hydrocarbons only contain hydrogen and carbon atoms

  • A hydrocarbon is any compound that is formed from carbon and hydrogen atoms only

  • So C10H22 is a hydrocarbons, but CO2 isn’t because it contains oxygen

Alkanes have all C-C single bonds

  • Alkanes are the simplest type of hydrocarbon you can get

    • They have the general formula CnH2n+2

    • The alkanes are a homologous series, a group of organic compounds that react in a similar way

    • Alkanes are saturated compounds, each carbon atoms forms four single covalent bonds

    • The first four alkanes are methane, ethane, propane, butane

Hydrocarbon properties change as the chain gets longer

  • The shorter the carbon chain the…

    • Less viscous

    • More volatile

    • More flammable

    • Lower boiling point

  • The longer the carbon chain is…

    • More viscous

    • Less volatile

    • Less flammable

    • Higher boiling point

Complete combustion occurs when there’s plenty of oxygen

  • The complete combustion in oxygen release lots of energy

  • Waste products are carbon dioxide and water vapour

    • Hydrocarbon + oxygen - Carbon dioxide + water

  • During combustion, both hydrogen and carbon is oxidised

  • Hydrocarbons are used as fuels due to the large amount of energy released

21.2-Fractional Distillation

Crude oil is made over a long period of time

  • Formed from the remains of plants and animals that died millions of years ago and through heat and pressure turned into crude oil

  • Non-renewable fuel

Fractional distillation is used to separate hydrocarbon fractions

  • Crude oil is a mixture of lots of different hydrocarbons

  • To separate them:

    • Heat until most has turned into a gas, bitumen won’t and will drain straight out

    • Gases enter a fractionating column which has a temperature gradient, hot at the bottom and cooler towards the top

    • Longer hydrocarbons have higher boiling points, so they condense back to liquids early on when they’re near the bottom, shorter hydrocarbon then take longer

    • End with crude oil mixture separated into different fractions

  • Fractions in crude oil are:

    • LPG

    • Petrol

    • Kerosene

    • Diesel Oil

    • Heavy fuel oil

    • Bitumen

  • Makes:

    • Lubricants

    • Petrol

    • Paraffin

    • Solvents

    • Detergents

21.3-Uses and Cracking of Crude Oil

Crude oil has various uses in modern life

  • Uses as fuel for transport

  • Petrochemical industry uses some of the hydrocarbons as a feedstock to make new compounds for uses in things like polymers, solvents, lubricants and detergents

  • All products are examples of organic compounds

Cracking means splitting up long-chain hydrocarbons

  • Short-chain hydrocarbons are more useful than long-chain hydrocarbons as they can make fuels so long-chains are cracked and broken into a short alkane and an alkene

  • Alkenes are used as a starting material when making lots of other compounds and polymers

There are different methods of cracking

  • Cracking is a thermal decomposition reaction-breaking molecules down by heating them

  • Catalytic cracking

    • Heat long-chain hydrocarbons until they are vaporised

    • Vapour is then passed over a hot powered aluminium oxide catalyst

    • Long-chain molecules are split apart on the surface of the specks of catalyst

  • Steam cracking

    • Heat long-chain hydrocarbons until they are vapourised

    • Mix them with steam and heat them to a very high temperature

Practice questions:

  • Properties of shorter chain hydrocarbons

    • lower viscosity, lower boiling point, higher flammable, more volatile

  • What is cracking?

    • A thermal decomposition reaction breaking molecules down by heating them

  • How to do catalytic cracking

    • Heat long chain hydrocarbons until they are vapourised and then pas over a catalyst

L

Chapter 21: Hydrocarbons and Crude Oil

21.1-Hydrocarbons

Hydrocarbons only contain hydrogen and carbon atoms

  • A hydrocarbon is any compound that is formed from carbon and hydrogen atoms only

  • So C10H22 is a hydrocarbons, but CO2 isn’t because it contains oxygen

Alkanes have all C-C single bonds

  • Alkanes are the simplest type of hydrocarbon you can get

    • They have the general formula CnH2n+2

    • The alkanes are a homologous series, a group of organic compounds that react in a similar way

    • Alkanes are saturated compounds, each carbon atoms forms four single covalent bonds

    • The first four alkanes are methane, ethane, propane, butane

Hydrocarbon properties change as the chain gets longer

  • The shorter the carbon chain the…

    • Less viscous

    • More volatile

    • More flammable

    • Lower boiling point

  • The longer the carbon chain is…

    • More viscous

    • Less volatile

    • Less flammable

    • Higher boiling point

Complete combustion occurs when there’s plenty of oxygen

  • The complete combustion in oxygen release lots of energy

  • Waste products are carbon dioxide and water vapour

    • Hydrocarbon + oxygen - Carbon dioxide + water

  • During combustion, both hydrogen and carbon is oxidised

  • Hydrocarbons are used as fuels due to the large amount of energy released

21.2-Fractional Distillation

Crude oil is made over a long period of time

  • Formed from the remains of plants and animals that died millions of years ago and through heat and pressure turned into crude oil

  • Non-renewable fuel

Fractional distillation is used to separate hydrocarbon fractions

  • Crude oil is a mixture of lots of different hydrocarbons

  • To separate them:

    • Heat until most has turned into a gas, bitumen won’t and will drain straight out

    • Gases enter a fractionating column which has a temperature gradient, hot at the bottom and cooler towards the top

    • Longer hydrocarbons have higher boiling points, so they condense back to liquids early on when they’re near the bottom, shorter hydrocarbon then take longer

    • End with crude oil mixture separated into different fractions

  • Fractions in crude oil are:

    • LPG

    • Petrol

    • Kerosene

    • Diesel Oil

    • Heavy fuel oil

    • Bitumen

  • Makes:

    • Lubricants

    • Petrol

    • Paraffin

    • Solvents

    • Detergents

21.3-Uses and Cracking of Crude Oil

Crude oil has various uses in modern life

  • Uses as fuel for transport

  • Petrochemical industry uses some of the hydrocarbons as a feedstock to make new compounds for uses in things like polymers, solvents, lubricants and detergents

  • All products are examples of organic compounds

Cracking means splitting up long-chain hydrocarbons

  • Short-chain hydrocarbons are more useful than long-chain hydrocarbons as they can make fuels so long-chains are cracked and broken into a short alkane and an alkene

  • Alkenes are used as a starting material when making lots of other compounds and polymers

There are different methods of cracking

  • Cracking is a thermal decomposition reaction-breaking molecules down by heating them

  • Catalytic cracking

    • Heat long-chain hydrocarbons until they are vaporised

    • Vapour is then passed over a hot powered aluminium oxide catalyst

    • Long-chain molecules are split apart on the surface of the specks of catalyst

  • Steam cracking

    • Heat long-chain hydrocarbons until they are vapourised

    • Mix them with steam and heat them to a very high temperature

Practice questions:

  • Properties of shorter chain hydrocarbons

    • lower viscosity, lower boiling point, higher flammable, more volatile

  • What is cracking?

    • A thermal decomposition reaction breaking molecules down by heating them

  • How to do catalytic cracking

    • Heat long chain hydrocarbons until they are vapourised and then pas over a catalyst