Energy transfers

    AQA
    GCSE

    Energy is a conserved quantity that cannot be created or destroyed, only transferred between distinct stores via mechanical, electrical, heating, or radiation pathways. Analysis requires the quantitative evaluation of kinetic, gravitational potential, and elastic potential stores, alongside the calculation of work done and power as the rate of transfer. Candidates must assess system efficiency, accounting for the inevitable dissipation of energy to the thermal store of the surroundings, and evaluate methods to reduce unwanted energy transfers through thermal insulation.

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    Objectives
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    Exam Tips
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    Pitfalls
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    Key Terms
    4
    Mark Points

    What You Need to Demonstrate

    Key skills and knowledge for this topic

    • Award 1 mark for stating that energy is transferred from the thermal store of the hotter object to the thermal store of the cooler object
    • Credit responses that link high thermal conductivity explicitly to a higher rate of energy transfer by conduction
    • Award 1 mark for correct substitution into the efficiency equation: useful output energy transfer divided by total input energy transfer
    • In insulation questions, credit the explanation that trapped air is a poor conductor which reduces the rate of energy transfer

    Marking Points

    Key points examiners look for in your answers

    • Award 1 mark for stating that energy is transferred from the thermal store of the hotter object to the thermal store of the cooler object
    • Credit responses that link high thermal conductivity explicitly to a higher rate of energy transfer by conduction
    • Award 1 mark for correct substitution into the efficiency equation: useful output energy transfer divided by total input energy transfer
    • In insulation questions, credit the explanation that trapped air is a poor conductor which reduces the rate of energy transfer

    Examiner Tips

    Expert advice for maximising your marks

    • 💡Use the phrase 'energy is dissipated to the surroundings' rather than 'energy is lost' to demonstrate understanding of conservation of energy
    • 💡When analyzing cooling curves, explicitly state that the rate of cooling decreases as the temperature difference between the object and surroundings decreases
    • 💡For Specific Heat Capacity calculations, always check mass units; if given in grams, convert to kg by dividing by 1000 before substituting

    Common Mistakes

    Pitfalls to avoid in your exam answers

    • Confusing 'temperature' (measure of average kinetic energy) with 'internal energy' or 'heat' in descriptive answers
    • Calculating efficiency as a value greater than 1 (or >100%) by incorrectly dividing input by output
    • Failing to convert time from minutes to seconds when calculating power (P = E/t) or energy transferred
    • Describing insulation as 'keeping the cold out' rather than reducing the rate of energy transfer from the thermal store

    Key Terminology

    Essential terms to know

    Likely Command Words

    How questions on this topic are typically asked

    State
    Explain
    Calculate
    Suggest
    Compare
    Determine

    Practical Links

    Related required practicals

    • •{"code":"Required Practical 2","title":"Thermal Insulation","relevance":"Investigating the effectiveness of different materials as thermal insulators"}
    • •{"code":"Required Practical 1","title":"Specific Heat Capacity","relevance":"Determining the SHC of a material by linking energy input to temperature change"}

    Ready to test yourself?

    Practice questions tailored to this topic