Conservation of energy

    AQA
    GCSE

    The principle of conservation of energy is a fundamental law of physics stating that energy cannot be created or destroyed, only transferred, stored, or dissipated. This topic explores the quantitative relationships between major energy stores, specifically kinetic, gravitational potential, and elastic potential energy. It necessitates an understanding of energy transfer pathways, the calculation of work done and power, and the analysis of efficiency within closed and open systems.

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    Objectives
    3
    Exam Tips
    3
    Pitfalls
    6
    Key Terms
    4
    Mark Points

    What You Need to Demonstrate

    Key skills and knowledge for this topic

    • Award 1 mark for stating the Law of Conservation of Energy: energy cannot be created or destroyed, only transferred, stored, or dissipated
    • Award 1 mark for identifying that 'wasted' energy is usually dissipated to the thermal store of the surroundings, causing a temperature rise
    • Credit responses that calculate efficiency correctly as (useful output energy transfer / total input energy transfer)
    • Award 1 mark for explaining that lubrication reduces friction and consequently reduces unwanted energy transfers to thermal stores

    Marking Points

    Key points examiners look for in your answers

    • Award 1 mark for stating the Law of Conservation of Energy: energy cannot be created or destroyed, only transferred, stored, or dissipated
    • Award 1 mark for identifying that 'wasted' energy is usually dissipated to the thermal store of the surroundings, causing a temperature rise
    • Credit responses that calculate efficiency correctly as (useful output energy transfer / total input energy transfer)
    • Award 1 mark for explaining that lubrication reduces friction and consequently reduces unwanted energy transfers to thermal stores

    Examiner Tips

    Expert advice for maximising your marks

    • šŸ’”When describing energy changes, always name the specific stores (e.g., 'chemical store' to 'kinetic store') rather than using vague terms like 'movement energy'
    • šŸ’”Check your efficiency calculation immediately: if the result is greater than 1 (decimal) or 100%, you have inverted the division
    • šŸ’”In calculations equating GPE lost to KE gained, remember that mass often cancels out, but showing the full substitution earns method marks

    Common Mistakes

    Pitfalls to avoid in your exam answers

    • Stating that energy is 'lost' or 'used up' rather than 'dissipated' or transferred to the thermal store of the surroundings
    • Calculating efficiency as a value greater than 1 (or >100%) by dividing total input by useful output instead of the reverse
    • Forgetting to square the velocity (vĀ²) when calculating Kinetic Energy, or failing to square root when rearranging to find velocity

    Study Guide Available

    Comprehensive revision notes & examples

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    Key Terminology

    Essential terms to know

    Likely Command Words

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    Practical Links

    Related required practicals

    • ā€¢{"code":"Required Practical 2","title":"Thermal Insulation","relevance":"Investigating the effectiveness of different materials as thermal insulators relates directly to reducing energy dissipation."}

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