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Energy Issues
Teaching about energy

There is no shortage of different approaches to the teaching of energy and this has resulted in much confusion and conflicting advice. These resources are intended to promote a consistent approach.

The key ideas about energy that are developed are:

 how energy is stored
 how energy is transferred
 conservation of energy
 dissipation of energy

These ideas are explored in a series of booklets that have been grouped into these three sections:

 Section 1: Temperature and energy
 Section 2: Energy stores and transfers
 Section 3: Conservation and dissipation

Click on the section titles to access the booklets.

What is energy?

Many school textbooks introduce energy by stating that it is difficult to say exactly what it is. This is a very reasonable place to start, since there is no easy answer to the question ‘What is energy?’ There are formal definitions, but these don’t really help students to understand what it is. It may be better to think of understanding energy as coming to know the character in a drama or a novel – getting to know the concept bit by bit as more of the story about its characteristics unfold.

There are at least three broad ways to think about the nature of energy.

Energy as a value. One way of thinking of energy is simply as a value that can be calculated. For any process you can, in principle, calculate the total energy before and find that it is the same as the total energy after. We could think of this as a ‘book-keeping’ approach.

Energy in many guises
. Hot things are seen as having ‘heat energy’, moving things as having ‘kinetic energy’, and so on. Energy can change itself from one such ‘guise’ to another – for example, when a fuel burns, ‘chemical energy’ is changed into ‘heat energy’. But little understanding is gained by naming ‘forms of energy’. It becomes just a classification game for its own sake.

Energy is energy
. A third approach is to think of energy as ‘fluid-like' – and the same kind of thing whether it is in a hot object or a moving one. It doesn’t change its nature but its location, perhaps becoming more concentrated in one region, or more spread out. Though the ‘energy as a value’ interpretation is entirely valid at appropriate levels, it is this third approach to energy that is promoted in these resources.

Transforming or transferring?

A very common way to introduce energy in KS3 has been the ‘forms of energy’ approach. A central feature of this approach has usually been the ‘energy circus’, in which a wide variety of phenomena are used to illustrate the many different kinds of ‘energy transformation’. However, the first version of the National Curriculum, and every version since, omitted any references to ‘forms of energy’ or ‘energy transformation’ and instead focused on the processes of ‘energy transfer’. The implication was that there should be a move away from thinking about energy as ‘changing from one form to another’ and to think of it as staying ‘the same kind of thing’, with the focus on where it is stored and how it goes from one place to another.

There is a concern that much of the talk involving forms of energy is just adding ‘verbal ornamentation’ to descriptions of changes. When you switch on a light in a room, the electrical current makes the lamp produce light. What deeper understanding is gained by calling this a change of electrical energy to light energy? In addition, students do not always find it easy to use the ‘correct’ labels to attach to these energy changes and often invent their own. So, a child taking part in a race might be seen as converting ‘food energy to running energy’. Textbooks, as well as children, also show variations in the terms used for ‘forms of energy’, which complicates things further.

Some would go so far as to say that the use of ‘forms of energy’ actually undermines the coherence of the energy concept, and this coherence across the physical world is its greatest strength.

It was these difficulties that led the National Curriculum to refer throughout to ‘energy transfers’. While the change in terminology from ‘transformation’ to ‘transfer’ seems slight, it actually signifies a fundamental change. Talking about energy transfer stresses the importance of thinking about energy as staying the same kind of thing but in going from place to place.

Often, however, the significance of the new terminology has gone unnoticed, with the term ‘transfer’ substituted for ‘transformation’. It is common to see phrases such as ‘chemical energy transferred to heat energy’. When you think about it the word ‘transfer’ makes no sense in this context.

Stores and transfers

Energy can be stored in different ways, so a secondary question is to ask what kind of stores are involved. Examples of different kinds of energy store are:


Because ‘energy is energy’ it does not change from one form to another – rather it can be transferred from one kind of store to another. This means that instead of talking about, for example, thermal energy, it is more helpful to talk about a thermal store of energy.

Energy can move from one store to another in various different ways. For example, energy is transferred from the engine to the wheels of a car through a series of gears and shafts; energy can be transferred from a battery to a lamp using an electrical circuit.

Examples of ways of describing transfer of energy are:

 by heating
 by radiation

Classification of transfer processes can be more problematic than sorting energy stores. The rules are not so clear, and these resources avoid such classification.

Conservation and dissipation of energy

The ‘book-keeping’ approach to energy is based on the ‘conservation’. Indeed, the observation that energy is conserved, unchanged in quantity, in all processes makes it a very important concept. An understanding that energy transfers from one place or system to another whilst neither increasing or decreasing, is of key importance. For this, students need to develop ideas about stores of energy and also about energy dissipation, which is the spread of energy from a store into wider surroundings so that it is so diluted as to be undetectable. The key point here is that ‘spread’ does not mean the same as ‘ceasing to exist’.
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