1. Chapter 17
Sources of Carbon Compounds
Learning Outcomes
• Identify natural gas and petroleum as
natural sources of hydrocarbons
• List the main uses of at least three fractions
obtained from the fractional distillation of
petroleum
• Describe the cracking of petroleum
fractions
2. Chapter 17
Sources of Carbon Compounds
Fossil Fuels
• A fuel is a substance which can undergo combustion in air
or oxygen to liberate useful heat energy.
• Fuels include substances such as wood, charcoal,
biomass fuel and fossil fuels.
• Fossil fuels (e.g. Coals, petroleum and natural gas) are
formed from the remains of animals and plants which died
millions of years ago.
• Due to high pressure and temperature, the remains of the
dead plants slowly turned into a solid black substance
called coal.
• Coal is considered to be a dirty fuel because it produces
air pollution when burned.
3. Chapter 17
Sources of Carbon Compounds
Natural Gas
• Natural gas is a mixture of hydrocarbons.
• Hydrocarbons are compounds consisting of hydrogen
and carbon only.
• Natural gas is considered a clean fuel because its has a
high energy value when burned and it emits lower levels
of harmful air pollutants into the air.
• Combustion of methane is:
CH4(g) + 2O2(g) CO2(g) + 2H2O(I)
4. Chapter 17
Sources of Carbon Compounds
Fractional Distillation of Petroleum
• Petroleum or crude oil is a black sticky liquid made
of a mixture of many hydrocarbons with molecules
ranging from one carbon atom to over 100 carbon
atoms.
• The smaller molecules are lighter and have lower
boiling points compared to the larger molecules.
• Petroleum is refined by separating the complex
mixture into simpler mixtures called fractions
before it can be used.
• This separation can carried out in the oil refinery
using fractional distillation.
6. Chapter 17
Sources of Carbon Compounds
Cracking of hydrocarbons
• Due to the rapid economic development of many
countries, there is an increasing demand for the lighter
fractions like petrol and naphtha, rather than lubricating
oil and fuel oil.
• Hence, there is a need to convert the heavier and less
useful fractions into the more useful fractions.
• This can be achieved through cracking.
• Cracking is the process of breaking large petroleum
molecules into smaller molecules with the use of heat and
catalyst.
• Types of cracking include: thermal cracking, catalytic
cracking and hydrocracking which are geared towards
producing specific products needed by the industry.
7. Chapter 17
Sources of Carbon Compounds
Problems and issues caused by fossil fuels
• Fossil fuels are non-renewable energy resources.
• The quantity of fossil fuels in the Earth is finite and they
cannot be replaced once they are used up.
• Coal is an unclean fuel producing much pollution which is
harmful to our environment.
• Therefore many countries have begun using cleaner fuel
and catalytic converters in cars, and developing better and
more efficient techniques of combustion to help reduce the
problems.
• This has led to a greater demand for clean fuels which
means that the price of oil has risen rapidly.
8. Chapter 17
Sources of Carbon Compounds
Alternative Energy Resources
• Alternative resources include the use of solar
energy, wind energy, tidal energy and hydroelectric
power.
• Another possible source of renewable energy will
come from plants. E.g. Palm oil is blended with
diesel to run cars.
• Lastly, scientists are experimenting with another
type of renewable fuel called biodiesel which can
be made from algae.
9. Chapter 17
Sources of Carbon Compounds
Quick Check
1. Name three types of fossil fuels.
2. Why is fractional distillation used to refine
petroleum?
Solution
10. Chapter 17
Sources of Carbon Compounds
Solutions to Quick Check
1. Coal, petroleum and natural gas
2. To separate it into simpler and more
useful fractions
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