Understandings:
- Fossil fuels were formed by the reduction of biological compounds that contain carbon, hydrogen, nitrogen, sulfur and oxygen.
- Petroleum is a complex mixture of hydrocarbons that can be split into different component parts called fractions by fractional distillation.
- Crude oil needs to be refined before use. The different fractions are separated by a physical process in fractional distillation.
- The tendency of a fuel to auto-ignite, which leads to “knocking” in a car engine, is related to molecular structure and measured by the octane number.
- The performance of hydrocarbons as fuels is improved by the cracking and catalytic reforming reactions.
- Coal gasification and liquefaction are chemical processes that convert coal to gaseous and liquid hydrocarbons.
- A carbon footprint is the total amount of greenhouse gases produced during human activities. It is generally expressed in equivalent tons of carbon dioxide.
Applications and skills:
- Discussion of the effect of chain length and chain branching on the octane number.
- Discussion of the reforming and cracking reactions of hydrocarbons and explanation how these processes improve the octane number.
- Deduction of equations for cracking and reforming reactions, coal gasification and liquefaction.
- Discussion of the advantages and disadvantages of the different fossil fuels.
- Identification of the various fractions of petroleum, their relative volatility and their uses.
- Calculations of the carbon dioxide added to the atmosphere, when different fuels burn and determination of carbon footprints for different activities.
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International-mindedness:
- The choice of fossil fuel used by different countries depends on availability, and economic, societal, environmental and technological factors.
- Different fuel rating systems (RON, MON or PON) are used in different countries.
- Ocean drilling, oil pipelines and oil spills are issues that demand international cooperation and agreement.
Utilization:
- Syllabus and cross-curricular links:
- Topics 5.1 and 5.3—enthalpy changes of combustion
- Topics 10.1 and 20.3—hydrocarbons and isomerism
- Topic 10.2 and option C.5—global warming
- Option C.8—solar cells
- Biology topic 4.3—carbon cycling
Aims:
- Aim 6: Possible experiments include fractional distillation and catalytic cracking reactions.
- Aim 7: Databases of energy statistics on a global and national scale can be explored here.
- Aim 7: Many online calculators are available to calculate carbon footprints.
- Aim 8: Consideration of the advantages and disadvantages of fossil fuels illustrates the economic and environmental implications of using science and technology.
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