Fossil Fuels

    OCR
    GCSE

    Fossil fuels (coal, oil, and natural gas) are non-renewable energy resources formed from ancient biological matter, serving as a primary source for base-load electricity generation. In physics, the focus is on the energy transfer pathway: chemical energy stores are depleted via combustion to increase the thermal store of water, producing steam to drive turbines and subsequently electrical generators. Candidates must evaluate the high energy density and reliability of these fuels against their significant environmental impacts, specifically the emission of carbon dioxide contributing to the greenhouse effect and global warming.

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    Objectives
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    Exam Tips
    4
    Pitfalls
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    Key Terms
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    Mark Points

    What You Need to Demonstrate

    Key skills and knowledge for this topic

    • Award 1 mark for defining non-renewable as a resource that is being used faster than it can be replenished
    • Credit responses that specifically identify Carbon Dioxide (CO2) as a contributor to the greenhouse effect/global warming
    • Award 1 mark for explaining reliability: fossil fuel stations can provide base-load electricity at any time, unlike wind or solar
    • Candidates must link Sulfur Dioxide (SO2) emissions specifically to acid rain, distinguishing it from global warming
    • Award 1 mark for stating that fossil fuels (Coal, Oil, Gas) have a high energy density compared to biofuels

    Example Examiner Feedback

    Real feedback patterns examiners use when marking

    • "You correctly identified that fossil fuels run out, but you must use the specific term 'non-renewable' for the mark."
    • "Avoid generic terms like 'pollution'. Specify that CO2 causes global warming or SO2 causes acid rain."
    • "Good point on reliability. To access higher marks, compare this directly with the intermittency of wind or solar power."
    • "You mentioned cost – be careful to distinguish between high start-up costs and lower running costs."

    Marking Points

    Key points examiners look for in your answers

    • Award 1 mark for defining non-renewable as a resource that is being used faster than it can be replenished
    • Credit responses that specifically identify Carbon Dioxide (CO2) as a contributor to the greenhouse effect/global warming
    • Award 1 mark for explaining reliability: fossil fuel stations can provide base-load electricity at any time, unlike wind or solar
    • Candidates must link Sulfur Dioxide (SO2) emissions specifically to acid rain, distinguishing it from global warming
    • Award 1 mark for stating that fossil fuels (Coal, Oil, Gas) have a high energy density compared to biofuels

    Examiner Tips

    Expert advice for maximising your marks

    • 💡When asked to 'Evaluate', you must provide both advantages (e.g., reliability, existing infrastructure) and disadvantages (e.g., CO2 emissions, finite supply)
    • 💡Distinguish clearly between 'start-up time' (fast for gas, slow for coal) and general 'reliability' (high for both)
    • 💡In 6-mark extended response questions, structure your comparison using three distinct categories: Environmental Impact, Reliability of Supply, and Economic Factors

    Common Mistakes

    Pitfalls to avoid in your exam answers

    • Confusing the greenhouse effect with ozone layer depletion – examiners reject references to the ozone layer for fossil fuel combustion
    • Using vague terms like 'pollution' or 'harmful gases' without specifying CO2 (global warming), SO2 (acid rain), or particulates (global dimming)
    • Stating that renewable energy can be 're-used' instead of 'replenished'; fuel is chemically altered during combustion and cannot be re-used
    • Incorrectly classifying nuclear power as a fossil fuel (it is non-renewable but not a fossil fuel)

    Study Guide Available

    Comprehensive revision notes & examples

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    Key Terminology

    Essential terms to know

    Non-renewable energy resources and depletion
    Energy transfers in thermal power stations
    Reliability and base-load power generation
    Environmental impact and the greenhouse effect

    Likely Command Words

    How questions on this topic are typically asked

    State
    Describe
    Explain
    Compare
    Evaluate

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