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93 | Strengthening teaching and learning of energy in Key Stage 3 science| Additional support pack | Appendix

© Crown copyright 200393 | Strengthening teaching and learning of energy in Key Stage 3 science| Additional support pack | Appendix

AppendixFurther resources

Further resources

Models and modelling

Where models and analogies areuseful in teaching

Scientists talking about the roleof models in science

Teaching about energy

Contents of this pack

Handout A1 – Further readingabout the use of models inscience, John Gilbert, Universityof Reading

Handout A2 – List of areas wheremodels and analogies are used inscience

Handout A3 – Professor JocelynBell Burnell, Dean of Science atthe University of Bath

Handout A4 – Professor Sir HarryKroto, Professor of Chemistry atthe University of Sussex. He iscurrently the president of theRoyal Society of Chemistry andwon the Nobel Prize forChemistry in 1996 for hisdiscovery of an allotrope ofcarbon, C60, calledbuckminsterfullerene

Handout A5 – Further readingabout the teaching of energy,Robin Millar, University of York,also distributed as part of theCPD participants’ pack

Suggestions for use of thematerials

For individual teachers with aparticular interest in the use ofmodels in science and scienceteaching

As part of an input to a networkmeeting or department meetingon the role of models in scienceor to set the wider context of theteaching models for energy

For individual teachers with aparticular interest in the use ofmodels in science and scienceteaching

Note: The original audio clips andshort PowerPoint presentationsto accompany them are availableon the CD-ROM distributed withthe CPD unit Strengtheningteaching and learning of energyin Key Stage 3 science

For individual teachers

Energy drinks Handout A6 – A resource thatexplores some of the sciencebehind the current growth of‘energy drinks’

For teachers in a department tobuild into a scheme of work as astarter activity for a topic onenergy or to make theconnection to energy in work onfood

Pupil Researcher Initiative materials – full details of the materials areavailable from the PRI website: http://www.shu.ac.uk/pri



Green heating

How safe are mobile phones?

Handouts A7 and A8 – Aresource that explores some ofthe science behind solar heating

Handout A9 – An ideas- andevidence-based resource thatexplores some of the sciencebehind the issues surroundingthe safety of mobile telephones

For teachers in a department tobuild into a scheme of work onenergy resources. The activitiescould be used to build on thework on group work in thescience session from theEffective teaching and learning inscience CPD unit

For teachers in a department tobuild into a scheme of work onenergy transfer

Types and forms of model John Gilbert, University of Reading

Models may be characterised in the following way:

• mental model: an entirely personal model, known only to an individual;

• expressed model: the version of a mental model conveyed to others;

• scientific model: an expressed model that is currently accepted by thescientific community as being of importance;

• historical model: a scientific model that has been superseded;

• curricular model: a simplified scientific or historical model included in ascience curriculum.

All thinking, not only that in science, is considered to consist of the formation anduse of mental models. These are known only to the individual having them.

When we express a mental model, for example by describing it, the outcome(mental models for the listeners!) is always somewhat different from that intended.Expressing a mental model often changes it for the ‘holder’.

A scientific model is an expressed model that has been subjected to rigorousexperimental testing, has been published and is in use at the frontiers of research,for example that of the AIDS virus.

A historical model is a scientific model that has been superseded at the frontiers ofresearch. It is, however, still useful for some routine tasks, for example the Bohrmodel of the atom after the publication of the Schrödinger model.

A curricular model is a scientific or historical model that has been simplified forinclusion in the curriculum, for example the ‘cloud-of-dots’ model conveying theidea of the time–probability distribution for the position of an electron in an atom.

Types and forms of model

Forms in which models in science can be represented

• Material (or concrete)

• Visual

• Mathematical

• Verbal/written

Examples of a model in a material (or concrete) form are: a ball-and-stick model ofa crystal structure; a cutaway, plastic, model of the human body; an orrery.

Examples of a model in a visual form are given by the very wide range of types ofdiagrams used in textbooks, for example with pictures, or sketches, or icons, asthe objects, and with logical relationships or time represented by connecting lines.

Mathematical models take the form of equations, for example of the Universal GasLaw.



Handout A1

Verbal/written models can be descriptions in words or writing of any of the othertypes, for example an analogy, ‘It is like ….’

Whilst one particular model may be represented in one or more of the above forms,few models are commonly represented in all of the forms.

Creating teaching models

It has been suggested that we can think of creating teaching models in thefollowing way.

The formation of a model

• The ‘target’ can be an aspectof reality that is to bemodelled. The aspect can bean object, an abstraction (aconcept), a system, an eventor a process. Important targetsin the National Curriculum are‘cells’, ‘particles’ and ‘energy’.

• The ‘source’ is some more familiar aspect of reality that is to be used todescribe the target. Important sources used in the National Curriculum are ‘the contour map’ for ‘cells’, ‘the billiard ball’ for ‘particles’, ‘the billiard ball’ and ‘the wave’ for ‘energy’.

• The ‘model’ is what is produced when a source is ‘mapped’ by the use ofanalogy onto a target: for example, when a cell is thought of as being like acontour map; when a particle is thought to be like a billiard ball; when energy isthought to be like, in different contexts, the movement either of particles or of awave.

The scope and limitations of a source

Any given source provides both valid and invalid comparisons with a target, forexample the camera used as a source to model the eye.

Valid comparisons

The eye Model of eye The camera

lens focuses light lens

choroid prevents reflection dark lining

eyelid protects eye lens cover

pupil admits light aperture

iris controls size of hole iris

retina receives image film


© Crown copyright 2003

Model

Source Target

Invalid comparisons

focusing focus by bending lens focus by moving lens

image capture cellular change chemical change on film

These ideas are largely drawn from: Gilbert, J. K., Boulter, C. J., Elmer, R. (2000).Positioning models in science education and in design and technology education.In: Gilbert, J. K., Boulter, C. J. (eds.), Developing models in science education.Dordrecht: Kluwer (pp. 3–17).

Publications about the use of models in teaching science

Models and modelling in science education, edited by J. K. Gilbert (Association forScience Education, 1993). This is out of print, but many university libraries have acopy.

Explaining with models, by J. K. Gilbert, in ASE guide to secondary scienceeducation, edited by M. Ratcliffe (Association for Science Education, 1998), pp.159–166.

Young people’s images of science, by R. Driver, J. Leach, R. Millar and P. Scott(Open University Press, 1996).

Developing models in science education, edited by J. K. Gilbert and C. J. Boulter(Kluwer, 2000).

‘Studies involving three-dimensional visualisation skills in chemistry: a review’, by H. Tuckey and M. Selvaratnam, Studies in Science Education, 21 (1993), 99–121.

On the ball – particle models for Key Stage 3 science, edited by M. Ratcliffe(University of Southampton, 2001).

School Science Review (SSR) – a journal of the Association of Science Education(quarterly). The SSR carries articles written by teachers and those concerned withscience education. It often contains articles about the use of models and analogiesto support the teaching of science.

Teaching energy and energy efficiency effectively: concepts and practice forprimary and non-specialist secondary teacher education (PSTS Project, 1998).Available from the ASE.



Where models and analogies are useful in teaching

Models are helpful to illustrate:

Objects that are too big

• Solar system

• An ecosystem

Objects that are too small or not seen easily

• Cell

• Heart

Processes that cannot easily be seen directly

• Digestion

• Erosion

Abstract ideas

• Particulate nature of matter

• Energy transfer



Handout A2

Transcript of an interview with Professor Jocelyn Bell BurnellProfessor Bell Burnell was asked to consider the role of models andanalogies in science:

‘Hello, I’m Jocelyn Bell Burnell. I am the Dean of Science at the University of Bath.

‘Some years ago I was involved in the discovery of a new kind of radio star calledpulsars. They showed up as a string of radio pulses.

‘To begin with, we had three possible models or pictures of what was producingthis string of pulses.

‘One idea was that it was an object that sent out a string of radio pulses like astring of bullets. Another idea was that it was an object like a lighthouse whichswung a beam around the sky, and each time the beam swept over us we saw apulse. And a third model, or picture, that we had was that it was like a jelly,quivering, and each time it quivered it sent out a shock wave which somehowturned into a radio pulse.

‘We didn’t know which of these models was right to begin with, although nowwe’ve actually settled on the lighthouse model: we think they’re rotating stars –swinging a radio beam round the sky like a lighthouse swings a beam around thesky.

‘This is the way science works: it generates models to help us visualise the world.Sometimes scientists use several models at a time; sometimes it’s fairly clear whichone is right – as in the case with the pulsars. And all of this is meant to help usunderstand.

‘You have got to remember, however, that you’re dealing with a picture or a model,not the real thing. The picture, the analogy, the model, may in fact let you down atsome point because it’s not the real thing. But it also has its uses.

‘Another famous analogy is to do with light. You can imagine light as a wave or youcan imagine light as a string of little particles, sometimes called corpuscles, morerecently called photons. The corpuscular theory was invented by Newton, and wayback in about 1786 this picture of light was used to describe what we now callblack holes – centuries ahead of Einstein.

‘It was work done by the Reverend John Mitchell.

‘You know that if a body has mass, gravity pulls on it. You try to pick a bottle up offthe floor, gravity pulls it back down. The Reverend John Mitchell assumed thatthese corpuscles of light also had mass and therefore gravity would act on them,and he asked how strong does the gravity have to be before the light cannotescape? That way he was able to work out how heavy a body would have to bebefore it became black because all the light got trapped. And that’s the idea of theblack hole.

‘Models, analogies, pictures, are at the heart of many aspects of science, and helpus visualise abstract ideas and things. But you do have to remember that they’renot the real thing and the picture may at some point let you down. But meanwhilethey provide very graphic and colourful ways of doing science.’



Handout A3



Transcript of an interview with Professor Sir Harry KrotoSir Harry Kroto discusses the role of models when developing insights intochemical structures. He starts by briefly describing how the experimentwas performed that led to the discovery of carbon-60.

‘Well, the experiment was very simple: it was to vaporise a piece of graphite and seewhether the carbon chains that we had seen in space could be made in thelaboratory, and they were. But then there was a fantastic surprise that one cluster ofsixty carbon atoms was much stronger than anything we’d expected and so we hadto think of an explanation. Why should a bundle of sixty atoms stick together and bestable?

‘We can’t see with our eyes these structures. We can interpret the signals and themathematical symbols such as sixty atoms, those numbers that we see, and we tryto work out how to put them together. We have a picture of an atom as somethinglike a ball on a billiard table; that’s a simple model which allows us to think in terms ofthese simple structures and put them together, and just as you put the balls on abilliard table in the triangle and they fit together in a nice structure, we try to think ofsome way of putting sixty balls together in a similarly nice structure, but we thoughtof it in terms of three dimensions, not just on a flat surface. And that’s how thescientist thinks: they see a signal that indicates that there’s something going on hereand they try to rationalise that, often in terms of simple images and simple patterns.

‘Everybody, particularly scientists, needs some image, or some “model”, to make thething more real to them. But those models can break down. I mean they are notperfect. They are related often to visual images. I mean, we say a ball or a billiard balland we see them on the table, and those patterns actually can apply in the physicaland the microscopic world; but in fact we know that that ball is a simplification of theatom – the atom is a small nucleus with an electron going round it. But to start offwith it’s absolutely vital for most physicists and most chemists – people, in particularchemists, who work with atoms – to put them into molecules, to think in simpleterms, and then go the next step to appreciate them in more complex ways, tounderstand the details and the more complex aspects. I often use an example ofcricket.

‘For instance, if you want to play cricket, the first thing when you start off is you seethe trajectory of the ball, OK. The bowler bowls the ball, and then, as you get tounderstand a bit more, the bowler puts some spin on it, OK. So we split our patternof what’s going on – a dynamic process, basically the trajectory of this ball. But thenwe add the complexity of the spin and how that affects it. But 95% of the motion isactually where the ball is going to bounce. And that aspect of science, of sport andscience, is very interesting, because that’s the way that we explain science – first ofall in simple terms, and then we add more complex aspects onto it.

‘And of course many students say, “Oh why didn’t they tell me that beforehand?” andthe answer is that they weren’t up to it. I mean basically, you have to learn nurseryrhymes first before you start to understand story telling, and then gradually build upwith more complex and more subtle and ethical issues. You can’t teach the child verycomplex matters until they have understood some of the more simple aspects.’

Handout A4


Teaching about energyRobin Millar, Department of Educational Studies, University of York

1 Introduction

Energy is an important idea in all branches of science, so you probably feel familiarwith it whether your background is in physics, chemistry or biology. You may thinkof energy as an idea that you understand, which should not therefore be toodifficult to teach.

In fact it is much less straightforward than it appears, for two main reasons:

1 In science, energy is an abstract, mathematical idea. It is hard to define‘energy’ or even to explain clearly what we mean by the word.

2 The word ‘energy’ is widely used in everyday contexts, including many whichappear ‘scientific’ – but with a meaning which is less precise than its scientificmeaning, and which differs from it in certain respects.

The first means that, in order to communicate the scientific idea of energy to younglearners, we have to simplify it – but still ensure that what we teach is clear anduseful, and provides a sound basis for developing a fuller understanding later. Thesecond means that we have to be very careful to disentangle the everyday usageof the word ‘energy’ from its scientific use, in order both to keep our own ideasclear and to avoid teaching pupils a potentially confusing mixture of the two.

2 Arguments and debates about the teaching of energy

Because of the two points above – particularly the first – there has been a long andoften heated debate about how energy should be taught in lower secondaryschool. Since the Nuffield O-level Projects in the 1960s, it has been common tointroduce ideas about energy in a non-mathematical way, in lower secondaryschool science courses. Some aspects of this approach, however, have beenseverely criticised – as inaccurate, or misleading, or an obstacle to later learning.This is discussed more fully in section 6 below. Some of the points made in thisdebate influenced the wording of the first science National Curriculum in 1989, andhave continued to influence later versions. The reason for the National Curriculum’schoice of wording, however, has not been fully grasped by some textbook authors,or some writers of examination questions – who have tried to implement the‘official’ approach but without sufficient understanding of it. The result is that manytextbooks at this level have energy chapters that are confused and confusing.Some contain incorrect (as opposed to merely simplified) explanations anddefinitions of terms. There is also quite wide variation in the terms used in differenttexts. Also many energy questions, including some in public examinations, areworded in obscure and unclear ways, and reward the ability to use taughtconventions which are not themselves scientifically accurate, rather than probinggenuine understanding of energy ideas.

Handout A5

It is not an overstatement to say that the teaching of energy is in a mess. Improvingthe situation is a long-term project. The starting point is to ensure that as manyscience teachers as possible have a clear understanding of the scientific energyconcept, and are aware of the issues about energy teaching that have beendiscussed and debated – so that they can teach about energy in as clear andaccurate a manner as the current curriculum, textbooks and examining systemallow them to, and can gradually help to influence these to change for the better.

3 Overview of this paper

A starting point for thinking about how to teach energy is to clarify your ownunderstanding. So the next section (section 4) looks at the scientific idea of energy.Following that, section 5 considers how the word ‘energy’ is used in everydaycontexts, how this differs from the scientific use of the term, and the possibleimplications of this. Section 6 then outlines and discusses some of the main issuesthat have been raised about energy teaching. Having outlined the issues anddifficulties, the remainder of these notes suggests how we might go about theteaching of energy, avoiding the worst pitfalls. Sections 7 and 8 propose a teachingsequence, starting with ideas about energy resources and leading on to looking atprocesses and events in energy terms. The final two sections then discuss brieflysome issues concerning the ideas of chemical energy and heat.

4 The scientific idea of energy

The Nobel Prize winning physicist, Richard Feynman, begins his discussion of thescientific idea of energy as follows:

There is a fact, or if you wish a law, governing all natural phenomena that areknown to date. There is no exception to this law – it is exact so far as is known.The law is called the conservation of energy. It says that there is a certainquantity, which we call energy, that does not change in the manifold changeswhich nature undergoes. That is a most abstract idea, because it is amathematical principle; it says that there is a numerical quantity, which does notchange when something happens. It is not a description of a mechanism, oranything concrete; it is just a strange fact that we can calculate some numberand when we finish watching nature go through her tricks and calculate thenumber again, it is the same.

(Feynman, 1963, p. 4-1)

There are several important points to note here. First, the most important ideaabout energy is that it is conserved – in every event and process, there is the sametotal amount at the end as there was at the beginning. It is this that makes energya useful quantity. It is not too strong to say that if energy was not conserved, itwould not exist as a scientific concept.

Feynman also emphasises that energy is an abstract, mathematical idea. It is aproperty of an object or system,1 which can be given a numerical value. It is notconcrete ‘stuff’. That means that we should talk about the energy of an object orsystem, but not about the energy in (or contained in, or stored in) it.2 However, I will


1 A ‘system’ just means a group of objects that can be treated as a single unit.

2 In much the same way, we would talk about the mass of something, but would not talk about the masscontained in it. Mass is a property of the thing. So is energy.


argue later (in sections 6.1, 7 and 8) that talking about energy as though it were akind of quasi-material substance that can be transferred from one place to anotheris almost unavoidable – and that this is a ‘good enough’ model to use whenintroducing the idea of energy to 11–14-year-olds, which will not form a seriousbarrier to later learning.

Finally, Feynman points out that energy is not a mechanism that explains howthings happen. It does not help us to understand how or why they happen. Whenwe introduce pupils to energy ideas, we are not providing them with an idea whichis of immediate practical use. Instead we are introducing them to a very general,overarching point of view that can be used to think about an enormously widerange of phenomena, across all the sciences. Energy provides an integratingframework. It can be intellectually satisfying to see diverse events from a singleunifying perspective. It is a ‘neat idea’, rather than a practically useful one. Later, ofcourse, it can become very useful, for anyone who pursues science further. But itonly really comes into its own when we can treat the ideas mathematically, andcalculate amounts of energy in different situations.

Feynman describes energy as ‘a numerical quantity, which does not change whensomething happens’. But he does not attempt to say what this numerical quantitymeasures. As several numerical quantities do not change when an event occurs(for example, the total mass, the total electric charge, the total momentum, andsome others), it is necessary to say something, however imperfect, about what thenumerical quantity we call ‘energy’ measures.

Energy is a measure of the amount of work an object or system is capable ofdoing, under ideal conditions. ‘Work’ is, itself, a precisely defined scientific term (theproduct of a force and the distance moved along its line of action). But even if wethink of ‘work’ in a looser, everyday sense, this definition of energy makes sense:when we have a lot of energy, we feel capable of doing lots of work; when we havelittle energy, we are incapable of doing much work. Energy is a measure of thecapacity of an object or system to do work.3

5 ‘Energy’ in everyday contexts

The earliest use of the word ‘energy’ (according to the Shorter Oxford EnglishDictionary) was around 1600, when it meant ‘force or vigour of expression’ – muchthe same sense as when we describe someone (or ourselves) as ‘energetic’, or ‘fullof energy’. The word was then adopted and used by scientists working during theperiod from 1780 to 1850 to develop a formal mathematical theory of processesinvolving heating and motion (now known as thermodynamics) as the name of aparticular property of an object or system – its capacity to do work. Since then,however, the term ‘energy’ has remained in everyday use, with both its original pre-scientific meaning, and also with some additional meanings that draw on thescientific idea but are not as precise or careful.

For example, in everyday discourse, energy is something we ‘use’ and ‘consume’.Phrases like ‘energy use’ and ‘energy consumption’ are common. We buy energyfrom the ‘energy utilities’, companies that sell us gas, oil or electricity, to use in our

3 Some people feel uncertain about this definition because they know (from the Second Law ofThermodynamics) that it is impossible to use all the energy of a hot object to do work. But this restrictionapplies only to what is possible in a cyclic process.

homes. Advice from electricity and gas supply companies tells householders howto reduce their energy usage, by insulating their homes or changing to moreefficient devices, like more modern central heating boilers or energy-saving lightbulbs. Government statistics published annually tell us about ‘energy consumption’in different sectors of the economy, such as industry, transport, domestic, and soon. Certain foods are said to give you a lot of energy, or to provide a quick energyboost when you need it. In this way of talking – which is not scientific though it isinfluenced by scientific ideas – energy is a commodity or a resource. We buy it anduse it. It comes in different forms, such as petrol, oil, gas, coal (and food).

This way of talking, however, can blur the distinction between the scientific andeveryday meanings of ‘energy’. We all become used to talking about energy inways that are not completely scientific – and, as a result, can come to think ofenergy in ways that are not in line with the scientific idea. This then poses problemsfor how we teach about energy, when we need to avoid the looser criteria thatapply to everyday discourse about ‘energy’, and use words and ideas moreprecisely and carefully.

6 Arguments and debates about teaching energy

The science National Curriculum includes ideas about energy resources and alsoideas that relate to the scientific energy concept, such as conservation of energy. Acommon way to develop these ideas, reflected in textbooks and in questions innational tests and GCSE papers, is to get pupils to think about events andprocesses in terms of energy transfers from place to place, or energytransformations from one ‘form’ to another. Some aspects of this approach have,however, been severely criticised, and there has been much debate about howbest to talk about energy ideas.

6.1 Abstract property or invisible ‘stuff’?

An outspoken critic of the way energy has been taught since the Nuffieldcurriculum projects of the 1960s is John Warren. Warren (1982) insists that energyis an abstract mathematical concept, and argues that teaching must start from itsscientific definition or else all that is taught is confused and largely meaningless.This definition (see section 4 above), however, requires that you already understandthe scientific idea of work, which in turn depends on understanding force. For mostteachers (and pupils), this approach is too abstract and formal. Warren acceptsthat it is only suitable for older students; in one article he writes:

There are just two ideas about energy that can, and should, be taught to allpupils below the sixth form:

(1) Energy is the name of an important bit of mathematics that you will learnabout if you ever study science or engineering at advanced level.

(2) A lot of people who do not know anything about it use the word ‘energy’ tomean all sorts of different things, most of which are silly. Take no notice ofthem.

(Warren, 1991, pp. 8–9)


But there are some things about energy (in particular about energy resources) thatevery citizen ought to know – and making energy a topic only taught to the fewwho continue their study of science into the sixth form is not an acceptablesolution.

For Warren, the fundamental flaw in a qualitative treatment of energy is that itmakes energy appear to be a ‘magic substance’, invisible and intangible, but ableto flow from place to place, changing its form as it goes, while staying constant inquantity. Others, however, see this as an acceptable, indeed a valuable, way ofsimplifying a difficult idea (for a discussion, see Duit, 1987).

In fact, it is hard not to think of energy as ‘something’ that flows, or is somehowtransferred, from place to place – rather than just thinking of it as a number thatdoes not refer to anything ‘real’. Imagine two objects, A and B, that interact in aprocess of some kind. The energy of A decreases – and the energy of B increasesby the same amount.

It is easy to see this as meaning that something (energy) has been transferred fromA to B.

So we develop a model of energy as a kind of intangible substance that flows fromplace to place, as a way of making sense of energy conservation. This is, however,a model – which is not exactly in line with the scientific idea of energy – and it ishelpful to keep this in mind as you use it. If we use this model carefully it can be avaluable tool for developing understanding. However, treating energy as a quasi-material substance can also lead to problems and difficulties, some of which arediscussed in sections 6.2 and 8.3 below.

6.2 Transfer or transform?

When we use a model of energy as something that can be stored in differentplaces (and ways) and can flow from place to place, it is tempting then to label thedifferent ‘forms’ that energy can take. Many textbooks and teaching schemes dothis. In a typical Key Stage 3 level textbook, these might be: kinetic, potential(perhaps split into gravitational potential and elastic potential), heat (or thermal),chemical, electrical, light.


A B

A B

energy of A gets less energy of B gets greaterby the same amount

energy transferred from A to B


This ‘forms of energy’ approach has, however, been the subject of much debate.One criticism is that pupils just learn a set of labels, which adds little to theirunderstanding. For example, one current textbook uses the example of a battery-powered golf buggy. It asks pupils to think of this in the following terms:

Chemical energy in the battery is transformed into electrical energy which is carriedby the wires to the motor. The motor then transforms this into kinetic energy as thebuggy moves.

This, however, adds nothing to the following explanation, which does not useenergy ideas:

The battery supplies an electric current which makes the motor turn. This thenmakes the buggy move.

A good general rule when explaining anything is that you should use the smallestnumber of ideas needed to provide an explanation, and not introduce any that areunnecessary.4 The explanation above using energy ideas fails this test. The sameapplies to many descriptions of devices as ‘energy converters’. Saying that a lightbulb ‘transforms electrical energy into light energy’ adds nothing to the simpler (andmore scientifically accurate) statement that it ‘emits light when there is an electriccurrent through it’.

The ‘forms of energy’ approach can also lead to analyses of situations whichintroduce unnecessary variables that do not contribute to understanding. Forexample, several textbooks discuss the energy changes when a person lifts anobject up to a height, describing this as chemical energy (in the person’s muscles)changing into kinetic energy (of the object as it moves upwards) which is finallystored again as gravitational potential energy. The intermediate stage here – thekinetic energy of the moving object – is not a useful quantity to know about. Theamount of kinetic energy tells us nothing useful about the overall process. Indeed itwill depend on the speed at which the object is raised. But the amount of potentialenergy which the object gains (and, to a reasonable approximation, the amount ofchemical energy lost by the lifter’s muscles) is the same, whatever the speed. Anenergy analysis that includes kinetic energy as one stage is simply introducingcomplexities that are irrelevant. In fact a much more useful analysis would be tonote that some of the chemical energy that is lost appears as thermal energy (inthe lifter’s muscles which rise in temperature), as well as the portion that appears inincreased gravitational potential energy of the object lifted – again focusing on theinitial and final states rather than intermediate ones. Another example of an analysisthat introduces unnecessary and unhelpful intermediate stages is discussed insection 8.4.

In some situations, the ‘forms of energy’ approach can lead to incorrect analyses ofprocesses. For example, one currently popular textbook includes a diagramshowing energy transfers in a moving car. It shows stored energy in the petrolbeing transferred to the car (as movement energy) and to parts of the car and thesurrounding air (as heat). This is an acceptable analysis for the period when the caris speeding up, and might seem plausible at first sight for a car travelling at asteady speed. But if a car is going at a steady speed, the amount of petrol (andhence of stored energy) in its tank is decreasing all the time, yet its speed (andhence its kinetic energy) is staying the same. A more correct energy analysis of a

4 This principle is sometimes called Occam’s razor, after the mediaeval philosopher who first stated it.


car moving at steady speed would show all of the energy stored in the petrolending up in the hotter parts of the car and its surroundings.

Another criticism of the ‘forms of energy’ approach is that it focuses attention in thewrong place, on the ‘form’ of the energy at different points, rather than on theprocesses by which energy is transferred from one object or system to another.Ellse (1988) argues that the latter is simpler, more useful and more important. Heproposes that we should not use any labels for forms of energy and just talk about‘energy’ being ‘transferred’ from place to place, rather than ‘transformed’ or‘converted’ from one form to another. While this works well for some processes,however, it works less well with others. For example, consider the simple situationof an object falling from a height or sliding down a smooth slope. Here we areinterested in the energy of the same object at the beginning and end5 – and itseems clearer to talk about its potential energy having been transformed (orconverted) into kinetic energy than to try to explain it using only the word ‘transfer’.Similarly, if we think of two similarly charged objects that are held close togetherand then released, the easiest way to talk about this in energy terms is as atransformation of potential into kinetic energy. To talk clearly about events in energyterms, we need both the terms ‘transfer’ and ‘transform’.

The National Curriculum largely avoids ‘forms of energy’ language, and talks ofenergy being transferred rather than transformed. Many textbooks and examinationquestions, however, have tried to retain some of the ‘forms of energy’ language butto avoid the word ‘transform’. They then talk about energy being transferred fromone form to another (e.g. ‘transferred from chemical energy in a person’s musclesto kinetic energy of something that they move’). This just doesn’t make sense –and certainly doesn’t make for clear communication. The way to avoid this isalways to use ‘transfer’ to mean from place to place.

Ellse (1988) also argues that it is misleading to use the term ‘electrical energy’ totalk about what is happening in an electric circuit.6 Energy is a property of an objector system – but in a simple electric circuit there is no object or system that has ameasurable (or even definable) amount of ‘electrical energy’.7 In simple circuits, anelectric current is a means of transferring energy from one place to another – fromthe battery to another component in the circuit, and perhaps on into theenvironment. Rather than thinking about amounts of energy in different places orforms, the more useful and interesting quantity is the rate at which the energytransfer is taking place. For this reason, it helps us think more clearly about theseprocesses if we talk (and think) about ‘energy being transferred by an electriccurrent’ or ‘energy being transferred electrically’, rather than ‘electrical energy’ –that is, as a way in which energy can be transferred rather than as a ‘form’ in whichit can be stored.

For similar reasons, ‘light energy’ can also cause problems. In most situations, weare more interested in the rate at which energy is being transferred from one place

5 Strictly speaking, gravitational potential energy is not the energy of the object alone, but of the object inthe field, i.e. of the object–Earth system.

6 He notes, though, that it is reasonable to talk about ‘electrical energy’ in other situations, such as in acharged capacitor, or any arrangement in which attracting electric charges have been separated.

7 While this is true for all the circuits we would want to discuss at Key Stage 3 or 4, a circuit which hasappreciable inductance or capacitance can store energy – and it would not be unreasonable to call this‘electrical energy’. However, this is not what is meant by ‘electrical energy’ in most textbooks that usethe term.

to another by light (or by any other kind of radiation) than in the amount of energystored. If we drew an imaginary boundary around a region in which there was light,then we could, in principle, calculate the amount of energy it contained – each lightphoton has a certain amount of energy, and we could multiply this by the numberof photons present. But this is rarely useful – and the number we got woulddepend on the size of the region we considered. In most situations, it is moreuseful to think of light as a way in which energy can be transferred from one placeto another.

6.3 Energy is not a cause

It is common to talk about energy as though it were the cause of events. Energy iswhat makes things happen, or makes them ‘go’. For example, Key Stage 3textbooks say things like:

Energy is needed to get jobs done, or to make things work.

Without energy nothing can ever happen.

You need energy to move and to work.

Ogborn (1986), however, points out that it is incorrect to say that ‘energy is whatmakes things happen’, or that something happens because of energy. Sostatements like the following are incorrect:

A ball keeps moving because it has kinetic energy.

Petrol makes a car go because petrol has energy.

A stone falls because it has potential energy.

One reason for avoiding causal statements like these is that energy is not amechanism. We need to use other ideas (like force) to explain how and why thingshappen. Looking at an event from an energy point of view might throw light onsome aspects of it – but does not help to explain how or why it happens. A secondreason is that energy is conserved. So it cannot explain why the process runs inone direction rather than the reverse (which would also conserve energy).

From a scientific point of view, it is entropy (or free energy), rather than energy, thatcan be said to ‘make things happen’. In any spontaneous event, entropy increases(ΔS > 0) (and free energy decreases (ΔG < 0)). These ideas, however, are generallythought to be too abstract and difficult to introduce at school level, though we hintat them when we use ideas like ‘energy spreading’ or going from a ‘concentrated’energy store to more ‘dispersed’ ones. So, while it is strictly incorrect to say that‘energy makes things happen’, in an introductory course it is reasonable enough tosay that an energy store of some kind is necessary for something to happen.

Searching for a simpler language to introduce these ideas to young learners,Ogborn (1990) suggests using the idea of difference to explain why things happen.Differences in temperature, concentration, shape (of a springy object), position in afield, or location (i.e. motion) can cause something to happen. When it does, thedifferences get less. Spontaneous events never result in greater differences. If theyappear to, it is always at the expense of a reduction of difference somewhere else.Ogborn and Boohan have developed these ideas into an interesting and novelteaching approach which is explained fully in three booklets (Boohan and Ogborn,1996a), and more briefly in a journal article (Boohan and Ogborn, 1996b). Although



the approach has not caught on in schools to any great extent, these materialscontain ideas that you may find useful, both to stimulate your own thinking aboutenergy and to suggest activities that you might incorporate in your teaching.

7 Teaching energy ideas

The previous two sections of these notes have raised several issues about energyteaching, and outlined some of the debates about it. So what should we do? Thissection and the next suggest a way of teaching about energy which takes accountof the issues that have been raised, introduces pupils to important ideas aboutenergy, and provides a sound basis for further learning.

A good place to begin the teaching of energy ideas is with energy resources(including food). There are ideas about energy resources and the way we use themthat are important for all citizens – and which all young people should be taught.We all have choices to make about our personal use of energy resources, and ourviews (for instance on how high the tax should be on petrol and diesel, or on themethods we should use to generate electricity) can influence national policy. As faras possible, these choices and decisions should be made on an informed basis.

Most pupils in Year 7 will know the word ‘energy’ from everyday discourse, andmany will associate it with fuels and food.8 Indeed, rather than emphasising theword ‘energy’, there are some advantages in focusing on the word ‘fuel’. We wantto avoid talking about ‘energy use’ and ‘energy consumption’, as this might causeproblems later, when we want to introduce the idea that energy is conserved. Wecan talk, however, about ‘fuel use’ and ‘fuel consumption’ without any inaccuracy.If you do use the word ‘energy’, it is better to talk about ‘using (or consuming)energy resources’ rather than about ‘using (or consuming) energy’.

The idea that most jobs need a fuel of some sort is likely to seem reasonable. Auseful introductory activity, which dates back to the original Nuffield courses, is toget pupils to divide a given list into ‘things that need a fuel’ and ‘things that do notneed a fuel’. (For example, a shelf holding up a row of books is an example ofsomething that does not need a fuel.) You can then go on from this to talk aboutthings like:

• the range of fuels we use in everyday life;

• the amounts used in different areas of life (homes, at work, transport, etc.);

• how the total amounts used have changed over time;

• the differences in amount (and type) of fuel used in different regions of the worldand the consequences of this.

All of these are important things for citizens to know about.

In discussing the range of fuels we use every day, electricity is almost certain to bementioned. At this level, it is acceptable to call electricity a fuel, pointing out that itis a ‘secondary’ fuel, which has to be generated using a ‘primary’ fuel (such as gas,or oil or coal). An important issue to discuss is the limited amount of fossil fuelsavailable, the relatively short period of time for which we have been using them andthe increasing rate at which we are doing so, and the need therefore to use them

8 For a summary of the main findings of research on pupils’ ideas about energy, see Driver et al., 1994.

carefully – perhaps mentioning concerns about the side effect of carbon dioxideproduction and its possible link with global warming.

This might lead on naturally to a discussion of renewable energy sources, such aswind, sunlight and waves. It does not seem very natural to call wind, sunlight andwaves ‘fuels’, or ‘energy resources’. Calling them ‘energy sources’, or simplytalking about ‘wind energy’ and ‘solar energy’, seems more natural – and unlikelyto cause many problems of understanding – even though you have not definedexactly what ‘energy’ means.

The idea that foods (or certain foods) are the ‘fuel’ for living organisms can also beintroduced here, as the basic idea is similar. Indeed, activities based on energyinformation (in joules) on food packaging can be a good way of introducing the ideathat amounts of energy can be measured – though at this stage it would not bewise (nor is there any need) to try to explain how this can be done or what the unitsmean.

Discussing the topics above also brings in (or can bring in) other ideas that arevaluable for every citizen to know something about. It is useful, for instance, toknow that some of the appliances we use at home use fuel much more quicklythan others – that an electric heater, for instance, uses fuel much faster than a lightbulb or a radio. The idea of ‘efficiency’ is also important. It takes less fuel to heatwater, or to keep it hot, in a well-insulated tank than in an uninsulated one. Anefficient central heating boiler uses less fuel to heat the water – because it wastesless heating the air. Compact fluorescent light bulbs are preferable to filamentbulbs, because they produce the same amount of light for less fuel (back at thepower station). Notice that all of these can be explained quite clearly using theword ‘fuel’ and without mentioning the word ‘energy’.

In the course of teaching these ideas, you are quite likely to find yourself talkingabout fuels as ‘energy sources’ and implying that energy can be stored in certainplaces and transferred to other places as a process proceeds. This is treatingenergy as a quasi-material substance – which is not strictly correct. However, it isalmost impossible to talk simply about energy without using this idea – and severalauthors have argued that it is not a serious hindrance to the later development of amore precise scientific understanding of energy (Duit, 1987; Kaper and Goedhart,2002a, b).

8 Thinking about events in energy terms

The next stage is to help pupils begin to think about events and processes inenergy terms. Here again, we will use a model of energy as a quasi-materialsubstance that can be stored in different places (and in different ways) and can betransferred from one object or system to another. However, it is important to takesome care about exactly how you do this, and the terms you introduce and use. Inthe approach suggested below, energy ideas are introduced qualitatively, but in away that leads easily to a more quantitative understanding at a later stage.

8.1 Where is energy stored at beginning and end?

A good starting point is to take some simple processes that can easily bedescribed or demonstrated in the lab, and ask pupils:



• what has got less energy at the end of this process than it had at the start?

• and what has got more energy at the end of this process than it had at thestart?

For reasons that are discussed later, it is better to ignore the stages in between andjust to concentrate on where energy is stored at the beginning and the end.

In order to answer these questions, pupils have to know how to ‘spot an energystore’. So, in discussion, you need to build up a list of ways in which we canrecognise an energy store:

• some chemicals (or combinations of chemicals9) have energy (chemical energy);

• something that is hot has energy (thermal energy)10;

• something that is moving has energy (kinetic energy);

• something elastic that is squeezed or stretched has energy (elastic potentialenergy);

• something that has been moved from its ‘natural position’ in a field has energy(e.g. lifted up in a gravitational field, two unlike charges moved apart, twoattracting magnets moved apart) (field potential energy).

It is not essential to use the ‘forms of energy’ labels in brackets after each item inthe list above, but they may be useful shorthand for referring to each of the ways inwhich energy can be stored.

Good examples to use for this activity are ones where the initial energy store, andthe places where energy is stored at the end, are reasonably easy to spot. Forexample:

1 a camping gas stove heating water in a saucepan;

2 a battery connected to a resistor coil, heating water in a beaker;

3 a battery connected to a motor, raising a load;

4 a block fired across the floor using an elastic band catapult;

5 a ball (or small vehicle) released at the top of a ramp and rolling down.

The first involves a fuel, which most pupils will accept as an ‘energy store’.11 Thereis less gas in the stove at the end (and hence less energy stored in it). Extendingthis to the chemicals in the battery (examples 2 and 3) is also not too difficult.Example 4 requires pupils to see the stretched elastic as another kind of ‘energystore’. Example 5 brings in the idea that energy is also stored in something that hasbeen raised up to a height.

Note that ‘electrical energy’ and ‘light energy’ are not included in the above list ofways that energy can be stored. The reason (as discussed earlier) is that it is rarelyuseful to think of energy as being stored in the form of electricity or light. These are

9 This point is discussed more fully in section 9.

10 You may prefer to call this ‘heat’ even though this is not strictly correct (see section 10 later). This alsoassumes that pupils already have some understanding of the difference between heat and temperature.

11 In fact it would be more accurate to say that the combination of fuel + oxygen is the energy store. Bothare needed to enable anything to happen. This is discussed more fully in section 9.


better thought of as ways in which energy can be transferred from one place toanother.

To develop these ideas:

• You might draw attention to the fact that the final store for energy in manyprocesses is the environment, which gets a little bit hotter. (For example, it canbe useful to consider two different ‘ends’ of the process in example 4 above: (i)just as the block leaves the catapult; (ii) when it has eventually come to rest.)

• You might note that often the energy starts in a single store but ends up inseveral different stores, one or more of which involves something getting hotter.

• You might discuss examples like a battery lighting a bulb. Rather than thinkingof light as the final energy store, it is better to think the process through to theend – and regard the objects that absorb the light, and get slightly warmer as aresult, as the final energy store.

• You might introduce examples involving mains electricity. Here the initial energystore is not electricity or ‘electrical energy’ – it is the fuel used in the powerstation to generate the electricity.

As well as identifying different ways in which energy can be stored, we can identifyseveral different ways in which energy can be transferred from one store to another:

• mechanically (by a force pushing or pulling something);

• electrically (by an electric current);

• by heating (due to a temperature difference12);

• by radiation (both electromagnetic and mechanical (e.g. sound)).

Energy is also transferred in a chemical reaction from the reagents to the products,but there is no simple word to describe this way in which energy is transferred. Thefirst two can be formalised later as mechanical work and electrical work, both ofwhich can be precisely defined and measured.

Some devices can be thought of as changing the way in which energy is beingtransferred, without actually storing any themselves. For example, we can think of amotor as having energy transferred to it electrically, and from it mechanically.

8.2 Conservation of energy

As Feynman highlights in the passage quoted in section 4 above, the mostimportant fact about energy is that it is conserved. The conservation of energy isone of the fundamental principles of science. So in talking about processes andevents in energy terms, we do not only want to describe where the energy is storedand how it is transferred. We also want to tell pupils that, in any event or process,the amount of energy lost by the store is equal to the sum of the amounts of energygained by the various reservoirs. Energy is a kind of book-keeping quantity. The‘energy books’ must balance at the beginning and the end. It should always tally.

12 Note that this implies that pupils understand the difference between temperature and heat (or thermalenergy) before they start on this. Strictly ‘heat’ is not the same thing as ‘thermal energy’, but at KeyStage 3 it would be a mistake to make too much of this. The important thing is that pupils can

We have, of course, no way of demonstrating to pupils that energy is conserved,as we do not, at this stage, have any way of measuring amounts of energy. It justhas to be asserted. But it is necessary to say something more about it, in order tomake it seem plausible – as most people’s intuition is that something is used up inall events and processes, and not that something is conserved.

Also, if energy is conserved, and there is always the same amount of energy at theend of a process as there was at the beginning, why do we need to ‘save energy’?These may appear to pupils to be contradictory viewpoints. You cannot just glossover this. The issue needs to be openly discussed, and the apparent contradictionresolved. The best solution is to introduce the idea of energy dissipation at thesame time as the idea of energy conservation (Solomon, 1982; Ross, 1988). Soalthough the total amount of energy is always the same after a process as it was atthe start, it is now more spread out, and less useful for doing things with in future.It is concentrated stores of energy, such as fossil fuels, that are valuable and needto be ‘saved’, or conserved.

8.3 Representing events and processes in energy terms

The set of ideas above gives us a way of talking about events and processesclearly and consistently in energy terms. The ways of storing energy and ways oftransferring energy used have been chosen so as to make the transition later to amore quantitative treatment as easy as possible.

A useful learning activity at this stage is to get pupils to represent some givenevents or processes diagrammatically, in energy terms. For example, a batteryconnected to a motor, raising a load could be represented as follows:

Here the rectangles show the initial and final energy stores – and the circle shows adevice which changes the way in which energy is being transferred.

Another way of representing the same process is to use a Sankey diagram:


(chemical)

transferredmechanically (dueto friction) and by

heating

transferred

energy of raised load

energy of parts of apparatusand environment that havegot hotter

energy storedin battery

transferred

battery motor

raised load

environment

(thermal)

(gravitational potential)

The first diagram has the advantage of showing how the energy is beingtransferred at different stages in the process. The second is better for showing therelative amounts of energy that end up in different places – which can be usefulwhen discussing efficiency, for instance. Another advantage of Sankey diagrams isthat the width of the arrows communicates visually the idea that energy isconserved – the total amount of energy is the same at beginning and end. It is agood idea to use both, as each captures a different aspect of the event.

A very useful pupil activity at this stage is to have pupils, either individually or insmall groups, consider several examples of events and processes, drawingdiagrammatic representations of them, using both of the types of diagram above.They will first need to be talked through several examples, to get the idea of theconventions to be used. The ability then to apply this to other examples is a goodindicator that a pupil has grasped the key ideas and is beginning to be able to thinkof events and processes in energy terms.

8.4 Choosing examples

It is important to take care in the examples you choose for the kind of activitydescribed above. Good examples are ones where the initial energy store and thefinal energy store(s) are clear. You should also make clear exactly which instantsyou are regarding as the start and the end of the event.

Focus on where the energy is stored at the beginning and the end of the event,and don’t worry too much about where it is in the middle – as this is rarely usefuland can often be positively unhelpful and misleading.

For example, consider a battery running a motor which turns a pulley (via a belt) and raises a weight.

Many textbooks represent this in energy terms, along the following lines:

chemical energy � electrical energy � kinetic energy � grav. potential energy + thermal energy(in battery) (in wires) (in moving parts (in load) (in motor, pulley)

of motor and belt)

Some parts of this, however, are problematic. The problem with electrical energyhas already been noted: energy is a property of an object or system; so what is theobject or system that has this electrical energy, and how much does it have? Thereisn’t one, and the amount could not be calculated. The rate at which energy isbeing transferred electrically is a much more useful quantity to consider.

The kinetic energy stage is also problematic. We certainly could identify objects thatare moving, and therefore have kinetic energy. But the amount of kinetic energythey have is irrelevant to an understanding of the overall process. If we replaced the


Weight

Motor

Battery


belt by a lighter one, but of the same strength, it would have less kinetic energy –but the process would continue as before. The kinetic energy of the moving parts isnot a useful quantity to know. There is no need to bother about it.13

It would be better to forget about these intermediate stages – remembering thatenergy is not a description of any mechanism – and focus on the initial and finalenergy stores. Then the process would be represented in energy terms as:

chemical energy � gravitational potential energy + thermal energy(in battery) (in load) (in motor, pulley, etc.)

It is also wise to avoid situations that involve something being maintained at aconstant speed, for example a car travelling at steady speed or an electric drill orfood-mixer (at least, until pupils can deal confidently with easier ones). In exampleslike these, the most obvious outcome is motion, so pupils are likely to see them interms of energy transfer from an initial store to the kinetic energy of the movingobject, perhaps with some being wasted to heat parts of the device and itsenvironment. This analysis is reasonable for the period in which the moving objectis speeding up. But while it is running steadily, the amount of kinetic energy it hasremains unchanged. So all of the chemical energy in the initial energy store is beingtransferred to parts of the device and their environment, heating them up.14 This isnot obvious, so these are not good examples of energy transfer to use to introducethese ideas.

9 Sorting out ideas about chemical energy

It is difficult to teach about fuels (including food) as energy resources withoutsaying, or at least implying, that these ‘contain energy’, or are ‘energy sources’, or‘energy stores’. It is more accurate, however, to think of the energy as being storedin a combination of chemical substances, rather than in one. A hydrocarbon fuel onits own can do nothing. It needs oxygen. The fuel is one part of a fuel–oxygensystem. Energy is released when the hydrocarbon reacts with oxygen. We mightjust as well call oxygen the fuel – and say that it needs a hydrocarbon to release itsenergy.

Ross (1993) discusses the misconceptions that can arise if we imply that fuels‘contain energy’, and argues for a fuller explanation that draws attention to the roleof oxygen. One widespread misconception is that energy is stored in the bonds ofsubstances, and released when these bonds are broken – rather like a fluid leakingout of a broken pipe. In fact energy has to be supplied to break bonds, rather thanreleased when they break.

When methane (a fuel) reacts with oxygen, the first stage is for the bonds in somemethane and oxygen molecules to be broken. Some energy is needed to do this,e.g. from a match. The fragments then recombine, to form molecules of carbondioxide and water vapour. This is rather like two unlike charges coming together,and releases energy – which is stored as thermal energy in the products of thereaction (hot carbon dioxide and water vapour). Because of the strengths of thevarious bonds involved, less energy is required to break the methane and oxygen

13 The same argument was used earlier when discussing the ‘lifting an object’ example in section 6.2.

14 You could think of kinetic energy being continually supplied to the moving object at the same rate as it isbeing transformed to thermal energy by the friction forces present – but it is simpler just to think in termsof the beginning and end states.

molecules apart than is released again when the fragments recombine to formcarbon dioxide and water. So once the reaction is triggered (by a match), it will thenrun continually as long as both methane and oxygen are present.

10 Sorting out ideas about heat

These notes have not made much use of the word ‘heat’ but have talked instead of‘heating’ as one of the ways in which energy can be transferred from one object toanother. The label suggested for the energy stored in a hot object was ‘thermalenergy’.

‘Heat’ is also a term that is used in everyday language in a way that is differentfrom its scientific meaning, and much less precise. Several articles have beenpublished pointing out some common misconceptions about heat, andinaccuracies in the way the word is used in teaching (Warren, 1972, 1976; Ogborn,1976; Mak and Young, 1987). Some have suggested that the noun ‘heat’ shouldbe dropped, and that we should refer instead to the process of ‘heating’ (Heath,1974, 1976; Summers, 1982). The latter has not caught on, but the argument mayhave encouraged some people to avoid using the forbidden word ‘heat’. It isnoticeable that, in the past 10 years or so, many textbooks have begun using theterm ‘thermal energy’. Unfortunately they rarely explain exactly what they mean byit – in particular, whether it is a synonym for ‘heat’ or for another well-defined (butdifferent) scientific term ‘internal energy’. In these notes, ‘thermal energy’ is asynonym for ‘internal energy’.

To understand the issues involved here, we need to think a bit harder about whatwe mean by ‘heat’. In everyday language, heat is something which hot objectspossess. If heat is added to an object, its temperature rises – and if it loses heat,its temperature falls. If two objects at different temperatures are placed in contact,then heat will spontaneously flow from the hotter one to the cooler one – and willcontinue flowing until both are at the same temperature. For young pupils, theseideas are not trivial. Many require some time to separate the two ideas of heat andtemperature.

The account above summarises the understanding of heat and temperature ofscientists from around 1750, when Joseph Black first separated the ideas of heatand temperature, until around 1840, when Joule and others began to sort out therelationships between work, heat and energy. It is really a potted version of thecaloric theory of heat. In this theory, heat is a quasi-material substance, which canflow from one place or object to another. The total amount of heat remains the


H

H

HH CO O

O O

HHC OO

O HH O

Energy required

Energy released

4 weak�bonds

4 strong�bonds

C H H H H �O O O O

bonds broken�(separate atoms)

8 strong bonds

same. This breaks down, however, when we think about situations wheresomething has its temperature raised by rubbing it (due to friction). This seems togenerate unlimited amounts of heat, which were not previously present – destroyingthe notion of heat as a conserved quantity.

Examples like this led scientists to develop a more complete model of thermalprocesses in which the internal energy of an object can be raised in two ways: bydoing work on it (e.g. by friction), or by placing it in contact with another object at ahigher temperature. The change of internal energy is the sum of the amount ofwork done on the object and the amount of heat transferred to it.

So it is not correct to say that:

Heat is a form of energy that is stored in hot objects. The higher the temperature ofan object, the more heat it contains.

This is a definition of ‘internal energy’, or ‘thermal energy’.

A better definition of heat is:

Heat is energy that is transferred spontaneously from an object at a highertemperature to one at a lower temperature.

Some people have argued, however, that it is unnecessary to introduce the term‘heat’ for this at all, and easier (and clearer) simply to talk about energy beingtransferred due to a difference in temperature – which we call the process of‘heating’. Bringing in the idea of heat is, they argue, an unnecessary complication.For instance, it involves reasoning about the interaction between a hot object and acold one as follows:

Internal energy in the hot object becomes heat which then becomes internal energyin the cold object.

Instead they suggest simply saying:

Energy is transferred from the hot body to the cold body; this process is calledheating.

It is difficult, however, to sustain this precision of language when talking to pupilsabout objects getting hotter and colder – and it is necessary to build on theireveryday knowledge. So the word ‘heat’ is likely to come into the conversation. Areasonable aim, therefore, of an introductory unit on thermal processes is todevelop an understanding similar to the caloric theory of heat – clearly separatingthe ideas of ‘temperature’ and ‘heat’. Then, when teaching energy ideas, asdiscussed in section 8 above, the term ‘thermal energy’ might be introduced –probably appearing to most pupils to be a synonym for ‘heat’.15 At a later stage,perhaps in Key Stage 4 but more probably at post-16 stage, the need for a moreprecise understanding of these ideas can be pointed out – and the differencebetween ‘heat’ and ‘thermal energy’ (or internal energy) made clear.


15 Indeed there is an argument for not introducing the term ‘thermal energy’ at all, but simply referring tothis form of energy as ‘heat’.

References

Boohan, R. and Ogborn, J. (1996a). Energy and Change. Introducing a newapproach. Activities for the classroom. Background stories for teachers.Hatfield: Association for Science Education.

Boohan, R. and Ogborn, J. (1996b). Differences, energy and change: a simpleapproach through pictures. School Science Review, 78 (283), 13–20.

Driver, R., Squires, A., Rushworth, P. and Wood-Robinson, V. (1994). Making Senseof Secondary Science, chapter 20. London: Routledge.

Duit, R. (1987). Should energy be introduced as something quasi-material?International Journal of Science Education, 9, 139–145.

Ellse, M. (1988). Transferring not transforming energy. School Science Review, 69(248), 427–437.

Feynman, R. (1963). The Feynman Lectures on Physics. Book 1. New York:Addison-Wesley.

Heath, N.E. (1974). Heating. Physics Education, 9, 490–491.

Heath, N.E. (1976). Heating. Physics Education, 11, 389.

Kaper, W. and Goedhart, M. (2002a). ‘Forms of energy’, an intermediary languageon the road to thermodynamics? Part I. International Journal of ScienceEducation, 24 (1), 81–96.

Kaper, W. and Goedhart, M. (2002b). ‘Forms of energy’, an intermediary languageon the road to thermodynamics? Part II. International Journal of ScienceEducation, 24 (2), 119–138.

Mak, S-Y. and Young, K. (1987). Misconceptions in the teaching of heat. SchoolScience Review, 68 (244), 464–470.

Ogborn, J. (1976). Dialogues concerning two old sciences. Physics Education, 11,272–276.

Ogborn, J. (1986). Energy and fuel – the meaning of the ‘go’ of things. SchoolScience Review, 68 (242), 30–35.

Ogborn, J. (1990). Energy, change, difference and danger. School Science Review,72 (259), 81–85.

Ross, K. (1988). Matter scatter and energy anarchy. The second law ofthermodynamics is simply common experience. School Science Review, 69(248), 438–445.

Ross, K. (1993). There is no energy in food and fuels – but they do have fuel value.School Science Review, 75 (271), 39–47.

Solomon, J. (1982). How children learn about energy, or Does the first law comefirst? School Science Review, 63 (224), 415–422.

Summers, M. (1982). Teaching heat – an analysis of misconceptions. SchoolScience Review, 64 (229), 670–676.

Warren, J.W. (1972). The teaching of the concept of heat. Physics Education, 7,41–44.


Warren, J.W. (1976). Teaching thermodynamics. Physics Education, 11, 388–389.

Warren, J.W. (1982). The nature of energy. European Journal of Science Education,4 (3), 295–297.

Warren, J.W. (1991). The teaching of energy. Physics Education, 26 (1), 8–9.




Pupil Researcher Initiative: Energy drinks

Handout A6

Energy drinks For teachers

Lucozade is perhaps the earliest example of an energy drink, because of its high glucose content. It gives your body an extra boost of energy and tops up your body fluids. What we now call energy drinks were developed in the Far East in the eighties. These have ingredients like caffeine, guarana and taurine, which give the body a more concentrated energy boost.

Guarana is nut-like seed of a climbing vine that grows in the Amazon basin in Brazil. It has been used for centuries by the indigenous people of the area as natural energy supplement. The Guarana berry contains a naturally-occurring form of caffeine which is 2.5 times stronger than the caffeine found in coffee, tea, and soft drinks. As with any other form of caffeine, people with heart problems or high blood-pressure should use caution when consuming large quantities of Guarana. Taurine has the effect of normalising the electrical activity of the heart muscle and can lower some people's blood pressure. A lot of people have a deficiency of taurine in their diet. In Japan, it's used to treat people with heart failure. However, excessive doses can lead to depression. The UK has become Europe's biggest consumer of energy drinks, and this may be because we work longer hours than we used to, and certainly more than people in most other EU countries. Energy drinks are also often used as a hangover cure.

Pupil Researcher Initiative: Green heating – teacher’s notes



Handout A7

❏ all types of electromagnetic radiation form a continuous spectrum

❏ when radiation is absorbed the energy it carriesmakes the substance which absorbs it hotter

❏ infrared radiation is absorbed by the skin and isfelt as heat

❏ different wavelengths of electromagnetic radiationare reflected, absorbed or transmitted differently

by different substances and types of surface

❏ dark, matt surfaces are good absorbers ofradiation

❏ light, shiny surfaces are good reflectors ofradiation

❏ thermal energy is the transfer of energy by waves,and particles of matter are not involved

Green Heating

Pupil Research Brief

Introduction

In this Brief pupils carry out simple investigations tofind out which colour and type of surface is best forabsorbing infrared radiation so that it can be used ina solar panel. They are given background informationabout solar panels and about infrared radiation fromthe Sun, and they are provided with informationabout how a scientific investigation is conducted.

They must plan an investigative procedure to answerthe question posed in Green Heating 3, or to testthe hypothesis set out in Green Heating 4, or to findout if the prediction made in Green Heating 5 iscorrect or not.

They should submit their plans for approval and thencarry out the investigation. Reports should be writtenafter the investigation has been conducted.

Experimental and investigative skills

• planning an experiment• obtaining evidence• analysing evidence and drawing conclusions• evaluating evidence

Prior knowledge

Before attempting this Brief pupils should havelearned about heat transfer by conduction,convection and radiation. Some knowledge of theelectromagnetic spectrum would be useful, andpupils should also know about reflection of light offplane surfaces.

UPIL

ESEARCHER

NITIATIVEIR

P

Green Heating 1

Green Heating 2

Green Heating 3

Green Heating 4 Green Heating 5

Investigation Investigation

Investigation

Report

Route through the Brief

Syllabus Coverage Subject Knowledge and Understanding

Teachers’ Notes

GH TN .01


Pupil grouping

Pupils could work in a number of groupings duringthis Brief. Suggestions are :

Initial briefing - whole class; teacher introduces topic and sets the context for the activities

Background paper - individuals or pairsGreen Heating 1

Carrying out - pairs or small groupsinvestigation

Analysis of results- pairs or small groups, or individually if the work is to be assessed

Communication - completion of written reports (individual or small groups). Small group presentation to whole class (optional).

Timing

This Brief is likely to take about 3 hours of classroomtime. The planning of the investigations can be set ashomework, as can the writing of the report.

Activities

The teacher should issue the pupils with the StudyGuide which provides pupils with a summary of whatthey should produce as they work through the Brief.It can also act as a checklist so that they can monitortheir own progress. Then hand out Green Heating 1to pupils. This gives information about how solarpanels use infrared radiation from the Sun to heat upwater. The Brief requires pupils to carry out aninvestigation concerned with the type of surface thatabsorbs infrared radiation best. The sheet GreenHeating 2 gives pupils information about theprocedures scientists use in carrying out researchwork.

There are 3 sheets that can be used by pupils as thestarting point for their investigation. Green Heating3 requires pupils to plan an experiment to answer thequestion “what colour surface is best at absorbinginfrared radiation ?”

Green Heating 4 sets out the hypothesis ‘a solarpanel with a matt black surface is better at heatingwater than a panel with a light shiny surface, sincedark surfaces absorb more heat’. Pupils are requiredto plan an experiment to test this hypothesis.

Green Heating 5 contains the prediction “if infraredradiation is a form of electromagnetic radiation likelight, then surfaces that reflect light will reflectinfrared radiation”. Pupils have to design anexperiment to test if the prediction is correct or not.In order to plan their experiments they can be issuedwith the Investigation Flowchart (see appendix toGeneral Teachers’ Notes). Pupils can use thisflowchart to help them plan their investigations. It isintended that pupils use only one of the investigationsheets - answering the question, testing thehypothesis or confirming or refuting the prediction. Itis up to the teacher to choose which sheet to use, orto use all three within the same class. Since pupils areasked to devise their own experiment, they mayrequire guidance as to what is possible to do with theequipment available in a school laboratory. It may beuseful to set out a bench with a range of materialsand apparatus and ask pupils to select only fromthese the equipment they will use to carry out theirinvestigations.

Investigation details

These will vary from class to class and it is notpossible to be specific about the investigations thatwill be carried out. However, some ways of carryingout the investigations are suggested below.

The question posed in Green Heating 3 could beanswered very simply by wrapping paper of differentcolours round thermometer bulbs and placing themequidistant from a source of heat radiation - a 60 Wlight bulb, for example.

Pupils need to be warned not to allow thethermometers to go above 100oC, or else they mayburst.

The hypothesis in Green Heating 4 can be tested bywrapping matt black paper round one small beakeror test tube containing some water, and shiny whitepaper round another. These are placed equidistantfrom a source of heat radiation and the temperaturesof the water in both beakers can be monitored atregular intervals.

The predictions in Green Heating 5 can be testedwith a similar experiment, as well as replacing thepaper with aluminium foil.

Using IT. Pupils could use temperature sensors orinfrared sensors to monitor changes in temperature.

Teachers’ Notes continued


GH TN .02



Safety issues

PLEASE NOTE: It is also important that you prepareyour own risk assessments for the practical work inthis Brief in the usual way.

Hot and radiant surfaces: danger of burns

If burned: hold affected area under flowing coldwater for at least 10 minutes. If anything other thanvery minor (shallow, less than 5mm diameter), seekmedical attention.

Assessment issues for Experimental andInvestigative Science (National Curriculumfor England and Wales, Northern IrelandCurriculum)

P Planning O Obtaining evidenceA Analysing evidence E Evaluating evidence

Three sheets taking pupils through the planningprocess:

Green Heating 3 Asking QuestionsGreen Heating 4 HypothesisingGreen Heating 5 Predicting

There is also an Investigation Planning Flowchartwhich pupils can use to help them plan theirinvestigation. The use of these sheets will have to betaken into account when assessing Skill Area P,although the full range of marks should be availablefor investigations based on Green Heating 4 andGreen Heating 5 since no investigation methods areprovided. Investigations based on Green Heating 3may be restricted to low-middle marks.

Skill Areas 0, A and E. All mark ranges should beavailable for investigations based on Green Heating 4and Green Heating 5. Low to middle marks for thosebased on Green Heating 3. Analysis and evaluation ofevidence will require pupils to demonstrateknowledge and understanding of absorption andreflection of electromagnetic radiation. How they dothis could influence their achievement in Skill AreasA and E.

Scottish syllabus coverage

Standard Grade Physics - Energy Matters

Further pupil research opportunities

Pupils could try to make a model solar panel. Ashallow box is lined with aluminium foil, plastictubing is wrapped around nails, so that it snakes upand down the length of the box. The tubing iscovered with black paper and a sheet of perspex isplaced on top. A trickle of water is fed in from thebottom and let out at the top. If this is angledtowards the Sun on a warm, sunny day, thetemperature of the water coming out of the panelshould be several degrees warmer than it was when itentered the panel.

Teachers’ Notes continued


GH TN .03

Pupil Researcher Initiative: Green heating – pupil’s sheets


Handout A8

❏ all types of electromagnetic radiation form a continuous spectrum

❏ when radiation is absorbed the energy it carriesmakes the substance which absorbs it hotter

❏ infrared radiation is absorbed by the skin and isfelt as heat

❏ different wavelengths of electromagnetic radiationare reflected, absorbed or transmitted differently

by different substances and types of surface

❏ dark, matt surfaces are good absorbers ofradiation

❏ light, shiny surfaces are good reflectors ofradiation

❏ thermal energy is the transfer of energy by waves,and particles of matter are not involved

Green HeatingSetting the SceneYou will investigate how solar panels work. You willcarry out an investigation based on a question, anhypothesis, or a prediction, relating to the science ofsolar panels

Route through the Brief


UPIL

ESEARCHER

NITIATIVEIR

P

GH .01

Syllabus Targets Science you will learn about in this Brief

Study Guide

Outcome Checklist

You will carry out an investigation based on aquestion, an hypothesis or a prediction. You willwrite a report of your findings. You can use anInvestigation Flow Chart to help you plan yourinvestigation. You should make sure you produce thefollowing items as you work through the Brief.

Green Heating 2

❏ investigation flow chart showing your plans

Green Heating 3,4 or 5

❏ report on investigation

Green Heating 1

Green Heating 2

Green Heating 3

Green Heating 4 Green Heating 5

Investigation Investigation

Investigation

Report



GH .02

Energy from the Sun can be harnessed and used productively for domesticand industrial purposes. Two of the most common ways of ‘collecting’ theSun’s energy are using solar panels (which produce hot water) andphotovoltaic cells (which produce electricity). Scientists are researching intoways of combining solar panels with photovoltaic cells in the same device inorder to use the Sun’s energy even more efficiently. However, in this PRB youwill concentrate on solar panels

Figure 1. How a solar panel works

Energy reaching the Earth from the Sun can be transferred by solar panelsto heat water moving around inside them. This solar energy is calledinfrared radiation. Radiation arriving at the outer surface is absorbed by thepanel. The energy is used to heat water sealed in the solar panel unit. Theenergy from this water is transferred to the domestic hot water system viathe heat exchanger. This hot water is used for houses, hospitals, offices orfactories. The more of the Sun’s energy that can be transferred to thewater, the better the solar panel is. We say it is more efficient.

If we know how to make solar panels more efficient we can reduce theamount of energy which comes from burning fossil fuels. Coal, oil andnatural gas are fossil fuels.

Read the sheet Green Heating 2 This tells you how scientists begin thinkingabout doing scientific investigations.

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cold water in

to domestichot watersystem

insulation

pump

sunlight

black absorbing panel

transparent cover direction of flow

heat exchangerwater

.


knowledge aboutthe subject

an idea toinvestigate

planning and doingthe investigation

working out whatthe results mean

new knowledgeabout the subject

telling other peoplewhat you have

learned

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Steps in an investigation

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GH .03

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GH .04

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You are going to plan and carry out an investigation to find out theanswer to the scientific question set out below. Solar panelsabsorb energy from the Sun. This type of solar energy is calledinfrared radiation.

Some coloured surfaces absorb most of the infrared radiationwhich reaches them. Solar panels with these types of surfacewould be good at heating up water. Other colours reflect a lot of theinfrared radiation which reaches them. Solar panels with thesetypes of surface would not be as good at heating up water.

What colour surface is best at absorbing infrared radiation?

Use the Investigation Flowchart to set out your ideas.

When you have finished the investigation, write a report on yourwork. Use your results to help you answer the question. Theanswer is not just the results - you have to think about what theresults mean - this will give you your answer. The answer maymean you now know something new about solar panels. Write areport, or plan a short presentation to the class, to tell them whatyou have learned.


��

You are going to plan and carry out an investigation to test thishypothesis:

A solar panel with a black matt surface is better at heatingwater than a panel with a light shiny surface, since darksurfaces absorb more heat.

The science knowledge that the hypothesis is based on is:

�� .

You now have to think about how you can get evidence showingthat the hypothesis is correct or not.


When you have finished the investigation, write a report on yourwork. Use your results to think about whether the hypothesis isright or not. The answer is not just the results - you have to thinkabout what the results mean - this will give you your answer.

You could then use your new knowledge to think of a newhypothesis about solar panels and how they work.

GH .05



GH .06

��

You are going to plan and carry out an investigation to test thisprediction:

If infrared radiation is a form of electromagnetic radiation, likelight, then surfaces which reflect light will reflect infraredradiation, and surfaces which absorb light will absorb infraredradiation.

The science knowledge that the prediction is based on is:

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You now have to think about how you can get evidence to see if theprediction is correct or not.


When you have finished the investigation, write a report on yourwork. Use your results to think about whether the prediction wascorrect or not. The answer is not just the results - you have tothink about what the results mean - this will give you your answer.

You could then use your new knowledge to think of a newprediction about solar panels and how they work.

Pupil Researcher Initiative: How safe are mobile phones?


Handout A9
























Further copies of this document are available from:

DfES PublicationsTel 0845 60 222 60Fax 0845 60 333 60Textphone 0845 60 555 60e-mail [email protected]

Ref: DfES 0445/2003


Produced by the Department for Education and Skills

Extracts from this document may be reproduced for non-commercial or training purposes on the condition that the source is acknowledged

www.standards.dfes.gov.uk/keystage3

www.dfes.gov.uk

department for

education and skillscreating opportunity, releasing potential, achieving excellence

09/03

Documents

Appendix Further resources - Amazon Web Serviceswsassets.s3.amazonaws.com/ws/nso/pdf/b254c261706bb8a16d3c8dd… · Appendix Further resources Further resources Models and modelling