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
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.
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)
Chapter 17 Sources of Carbon CompoundsFractional 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.
Chapter 17Sources of Carbon CompoundsFractional Distillation
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.
Chapter 17 Sources of Carbon CompoundsProblems 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.
Chapter 17 Sources of Carbon CompoundsAlternative 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.
Chapter 17Sources of Carbon CompoundsQuick Check1. Name three types of fossil fuels.2. Why is fractional distillation used to refine petroleum? Solution
Chapter 17 Sources of Carbon CompoundsSolutions to Quick Check1. Coal, petroleum and natural gas2. To separate it into simpler and more useful fractions Return