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Chemistry
Organic Chemistry 1 - Hydrocarbons
➢ Contains carbon + hydrogen atoms only

Homologous Series
➢ Group of molecules with the same general formula
➢ Similar chemical properties gradually changing physical properties

Alkanes (CnH2n+2)
➢ Saturated – single bond only
No
...
1 of carbon
2
3
4

Name
Ethene
Propene
But-1-ene
But-2-ene

Molecular formula
C2H4
C3H6
C4H8

Structure Formula

Organic Chemistry 2 – Fuels
Fossil fuels
➢
➢
➢
➢
➢
➢

Burn easily
Produce little ash or smoke
Large amounts of energy when burnt
Easy to store and transport
Coal, natural gas, crude oil
All non-renewable fuels

Crude Oil
➢ Mixture of hydrocarbons
➢ Collects in porous rock
➢ Pumped up from under the ground and taken by pipes or tankers to your refineries

➢ Finite resource
➢ Used as fuels on as feedstock for the petrochemical industry
➢ Must be separated similar carbon chain length by fractional distillation
Fractional name

Use

NO of C

BP

Ease of ignition

Viscosity

Gases

Domestic
heating
Fuel for cars
Fuel for
aeroplanes
Fuel for cars and
trains
Ships and power
station
Roads and roofs

1-4

Low

High

low

735

High

Low

High

Petrol
Kerosene
Diesel oil
Fuels oil
Bitumen

Fractional Distillation
➢ Heated strongly
➢ Vapours rise and then condense when they reach a cool enough point
As chains get longer:
➢ Bp increases
➢ Fractions become more viscose
➢ Less volatile
➢ Harder to burn

Cracking
➢ Breaks down larger less useful long chain hydrocarbons into smaller more useful
alkanes an alkene
➢ cracking meets the demand
➢ add catalyst and heat
➢ E
...
C8H18 → C5H12 + C3H6
In the lab:
➢ Larger alkane is soaked in ceramic wood and put in boiling tube with a catalyst
➢ Heated and vapoured

➢ Gases are insoluble so are collected over water

Alternative Fuels
➢ Hydrogen – it is cleaner or Bio- fuels
➢ Exothermic combustion
➢ Only water products are H20
➢ No CO2
➢ Can be made from water
Problems:
➢ Gas = hard to transport and to store – heavy tanks are needed
➢ Very flammable
➢ Not readily available
➢ Does not occur naturally – electrolysis

Combustion of fuels
Complete
• Excess oxygen
• Only CO and H2O is produced
• Fuel + Carbon → CO2 + H2O
• Maximum amount of energy is
released

Incomplete
• Insufficient oxygen
• Carbon monoxide, soot and water
produced
• Fuel + oxygen → CO + H2O
• Less energy is released

Incomplete combustion occurs in:
• Car engines where petrol burns producing carbon monoxide and soot
• Poorly ventilated rooms with coal or gas fires
When using a Bunsen burner:
• A yellow flame indicates that combustion is incomplete
• A blue flame indicates that combustion is complete
▪
▪
▪
▪
▪

Soot → carbon
Carbon monoxide → a tasteless colourless odourless toxic gas
Drowsiness → coma then death
Combines with haemoglobin and stops it carrying oxygen to cell
If poisoning is advanced, then blood transfusion is the only cure

Environmental consequences of burning fossil fuels
Sulphur dioxide
• Coal includes natural impurities
• Acid rain
• Crops don’t grow well in acid soil
• Acidity kills fish
• Weathering increases
Solved by:
• Removed from fuels before burning
• Neutralise the emissions with CaCO3

Renewable or not?
Examples
Advantages

Disadvantages

Oxides of Nitrogen
• High temps cause N2 and O2 to react
• Contributes to acid rain when it is
dissolved in rain forming nitric acid
• Respiratory diseases like asthma
Solved by:
• Catalytic converts No2 to harmless N2

Fossil fuels
Yes
-Petrol
-Natural gas (Methane)
-Easily ignited
-Liquid at room temp – easily
stored
-Take millions of years to form
-Finite resource

Hydrogen
Only if used for the electrolysis of
water
-Hydrogen
-Easily ignited
-Releases large amounts of
energy per gram
-Electricity makes it expensive
-Fewer filling stations



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