Energy

    OCR
    GCSE

    Energy is defined by the principle of conservation: it cannot be created or destroyed, only transferred between stores, dissipated to the surroundings, or stored in less useful ways. Candidates must quantify these transfers using equations for kinetic, gravitational potential, and elastic potential energy, alongside calculations for power and efficiency. The topic necessitates a robust understanding of thermal energy transfer mechanisms, the specific heat capacity of materials, and the critical evaluation of renewable versus non-renewable energy resources within national and global contexts.

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    Objectives
    4
    Exam Tips
    4
    Pitfalls
    5
    Key Terms
    5
    Mark Points

    What You Need to Demonstrate

    Key skills and knowledge for this topic

    • Award 1 mark for explicitly stating the starting and ending energy stores (e.g., 'chemical store to thermal store') rather than vague 'types' of energy.
    • Credit responses that correctly substitute values into the kinetic energy equation (0.5 × m × v²) before attempting rearrangement.
    • Candidates must link low thermal conductivity directly to a reduced rate of energy transfer by conduction.
    • Award 1 mark for identifying that 'wasted' energy is usually dissipated to the thermal store of the surroundings.
    • For efficiency calculations, credit the correct selection of useful energy output divided by total energy input, expressed as a ratio or percentage.

    Example Examiner Feedback

    Real feedback patterns examiners use when marking

    • "You correctly identified the energy transfer, but you must specify the 'store' (e.g., thermal store) to gain the mark."
    • "Your calculation is correct, but you forgot to convert mass from grams to kilograms—always check units first."
    • "Good description of the insulation experiment. To improve, explain *why* the air gap reduces heat loss using the concept of conduction."
    • "You stated the energy is lost; remember to say it is 'dissipated to the surroundings' to show understanding of conservation."

    Marking Points

    Key points examiners look for in your answers

    • Award 1 mark for explicitly stating the starting and ending energy stores (e.g., 'chemical store to thermal store') rather than vague 'types' of energy.
    • Credit responses that correctly substitute values into the kinetic energy equation (0.5 × m × v²) before attempting rearrangement.
    • Candidates must link low thermal conductivity directly to a reduced rate of energy transfer by conduction.
    • Award 1 mark for identifying that 'wasted' energy is usually dissipated to the thermal store of the surroundings.
    • For efficiency calculations, credit the correct selection of useful energy output divided by total energy input, expressed as a ratio or percentage.

    Examiner Tips

    Expert advice for maximising your marks

    • 💡Always use the term 'store' (e.g., 'gravitational potential store') to secure AO1 marks; avoid saying 'gravity energy'.
    • 💡In 6-mark extended response questions on insulation, structure your answer: Material Property → Mechanism (Conduction/Convection) → Effect on Rate of Transfer.
    • 💡When calculating velocity from Kinetic Energy, write down the rearranged formula first (v = √(2KE/m)) to prevent algebraic errors.
    • 💡Check the command word: 'Describe' asks for the process or trend, while 'Explain' requires the scientific reason (e.g., particle collision).

    Common Mistakes

    Pitfalls to avoid in your exam answers

    • Stating that energy is 'used up' or 'lost' rather than 'dissipated' or 'transferred to the surroundings', violating the conservation of energy principle.
    • Forgetting to square the velocity (v²) when calculating Kinetic Energy, or failing to square the speed before multiplying by mass and 0.5.
    • Confusing 'heat' (energy in transit) with 'temperature' (measure of average kinetic energy of particles) in specific heat capacity questions.
    • Failing to convert time from minutes to seconds when using the Power equation (P = E/t).

    Key Terminology

    Essential terms to know

    Energy stores and transfer pathways
    Conservation, dissipation, and efficiency
    Power and work done
    Specific Heat Capacity and thermal insulation
    National and global energy resources

    Likely Command Words

    How questions on this topic are typically asked

    Calculate
    Describe
    Explain
    Suggest
    Evaluate
    Compare

    Practical Links

    Related required practicals

    • •{"code":"PAG P1","title":"Specific Heat Capacity","relevance":"Measuring energy transfer to heat a metal block"}
    • •{"code":"PAG P2","title":"Thermal Insulation","relevance":"Investigating effectiveness of materials as insulators"}

    Ready to test yourself?

    Practice questions tailored to this topic