Revision Notes

1.7.1 Energy

The Conservation of Energy

  • Energy is the capacity of something to do work:
    • If something contains a store of energy it is able to do work
    • If something does not store energy then it will not work
  • The law of conservation of energy states that:
    • Energy cannot be created or destroyed, it can only change from one form to another
  • What this means is that the total amount of energy in a closed system remains constant, although how much of each form there is may change

Some examples:

  • A falling object (in a vacuum): Gravitational potential energy → Kinetic energy
  • A gas cooker: Chemical → Internal (Heat)
  • An LED (Light Emitting Diode): Electrical → Light


Extended Only

Conservation of Energy in Multiple Stages

  • Many processes involve several steps before energy ends up in its final form

For example:

  • A fossil fuel power station takes chemical energy (the fuel) and uses it to produce electrical energy, but the individual steps are:
Chemical → Internal (heat) → Kinetic (steam) → Kinetic (turbine and generator) → Electrical

Types of Energy

  • Energy can exist in a number of forms
    For your IGCSE examination you are expected to know about the following:

Energy types table, IGCSE & GCSE Physics revision notes


Energy stores and transfers worked example (1), IGCSE & GCSE Physics revision notes

Worked example showing how energy is stored and transferred


Energy Transfer

  • In addition to the six forms of energy mentioned above, there are four ways in which energy can be transferred from one form to another:

Energy transfer table, IGCSE & GCSE Physics revision notes

Extended Only

Energy Dissipation

  • When energy is transferred from one form to another, not all of the energy will end up in the desired form (or place)
  • This lost energy often ends up being dissipated (spreading out into the environment), usually in the form of heat, light or sound


Transfers and stores of energy, IGCSE & GCSE Physics revision notes

Diagram showing the forms of energy transfers and stores


Exam Tip

The classification of energy into forms and transfers, as mentioned above, is a fairly new approach and so there is a chance that you may have been taught this topic slightly differently or have come across different approaches elsewhere.

Don’t worry if this is the case, but you will need to become familiar with the above classification as there is a very good chance that it will be used in your examinations.


Author: Jenna

Jenna studied at Cardiff University before training to become a science teacher at the University of Bath specialising in Biology (although she loves teaching all three sciences at GCSE level!). Teaching is her passion, and with 10 years experience teaching across a wide range of specifications – from GCSE and A Level Biology in the UK to IGCSE and IB Biology internationally – she knows what is required to pass those Biology exams.

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