Conceptions of energy

A topic in science concepts and learners' conceptions and thinking

Science teaching involves teaching scientific concepts, yet these may be difficult to completely characterise, and may prove difficult for many learners to master (a very brief introduction to why this might be can be found at the foot of this page).

This page introduces some issues related to the concept of energy, with links to examples discussed in more detail elsewhere on the site.

The concept of energy

The concept of energy is both one of the most important in the whole of science, and one of the most abstract concepts that is introduced in secondary school science.

The difficulty of the topic is reflected in its historical development – the modern notion of energy had quite a convoluted 'gestation'. This perhaps explains why there continues to be much debate about how the subject should be taught. (For example, should learners be taught about energy being transformed from one form to another, or transferred form one reservoir to another?)

https://spark.iop.org/energy-cpd-videos(opens in a new tab)

It is not unusual for scientific ideas to need some simplification when introduced at introductory level. In effect, a scientific concept becomes represented in the curriculum in the form of a curricular model. As one example the (U.K. based) Institute of Physics (IoP), has developed an approach to teaching the topic that is recommended for secondary level. The IoP suggests,

"Energy is about doing calculations; it is a useful tool for predicting what can happen but shouldn't be used to explain phenomena."

https://spark.iop.org/energy-cpd-videos

Conservation of energy

A key scientific principle is that energy is conserved, i.e., energy can not be created nor destroyed. (It often used to be taught that "energy can neither be created nor destroyed, it can only change its form", but this is to be avoided in a teaching model is used which follows the transfer rather than the transformation approach.)

It has been suggested that the principle of conservation of energy fits with people's intuitions,

"The principle of the conservation of energy, that is to say, the conviction that so-called perpetual motion is impossible, must indeed be deeply rooted, for it can be shown to have coloured the thought of mankind long before it was explicitly formulated by science. This fact Mach endeavoured to prove by examples from the history of mechanics, especially by the ways in which the law of the lever and fundamental laws of hydrostatics were deduced and formulated by Archimedes and Stevinus."

Cassirer, 1950

The principle is now widely accepted as a universal law of nature, that is something that applies anywhere in the universe – although that has not been directly tested of course.

Despite, this, in practice many scientists assume that conservation of energy must always occur in any process:

"[The generalisation] was soon to be known as the law of conservation of energy, and it surpassed all earlier physical principles in the range of its concrete applications. Once conceptual assimilated, furthermore, it seemed so nearly inevitable that it was sometimes accorded an a priori status."

Kuhn, T. S.,

Strictly, all scientific knowledge must be considered provisional (open to challenge in the light of new information), but conservation of energy is considered by most scientists as extremely well established. The abstract nature of the energy concept is reflected in how Nobel laureate Richard Feynman explained energy conservation,

"Of all the conservation laws, that dealing with energy is the most difficult and abstract, and yet the most useful. … we have a number which is not changed in time, but this number does not represent any particular thing … What we have discovered about energy is that we have a scheme with a sequence of rules. From each different set of rules we can calculate a number for each different kind of energy. When we add all the numbers together, from all the different forms of energy, it always gives the same total. But as far as we know, there are no real units, no little ball bearings. It is abstract, purely mathematical, that there is a number, such that whenever you calculate it does not change. I cannot interpret it any better than that."

Feynman, 1965, pp.68-70.

This perhaps gives some insight into why the topic is often found challenging to learn (and teach well), and why learners often present with alternative conceptions about energy. 1

Energy degradation

Although energy is always conserved, it is not always available to do useful work for us. (Explaining why in common parlance, people are told to 'conserve energy' as though they could ever do otherwise!) As systems tend to evolve to states of greater entropy, energy becomes less useful for practical purposes (it is sometimes said to become of lower quality – we might think of it as being less concentrated and more widely dispersed). In school science, entropy is not usually introduced till senior levels, so is unavailable to help teach introductory accounts of energy.

This is especially important given the global social importance of energy/power 'supply' and the related topics of the exhaustion of fossil fuels and their contribution to climate change: making teaching the topic an imperative in schools.

Alternative conceptions

There are many alternative conceptions (misconceptions) relating to energy. This is not an exhaustive account!

"…a Pakistani nuclear engineer once advised the government that the jinn that appear in the Quran as well as the Thousand and One Nights were made by Allah from fire and, as such, could be used as source of energy to combat the permanent energy crisis that bedevils [sic] the country."

Tariq Ali, 2015
Energy is produced/used up in metabolism

As energy is always conserved, it cannot be created or destroyed in metabolic processes. However, learners may think that respiration produced energy, or that photosynthesis somehow creates it.

Although one assumes scientists do not share these conceptions, they may sometimes use language that can be understood that way:

  • "[mitochondria] are the energy producing organelles, they make energy in most cells" – Dr. Siddhartha Mukherjee (medical oncologist at Columbia University)
  • "The leaves [of an oak tree] contain the miraculous [sic] substance chlorophyll, which uses the rays of light in order to transform energy into matter." – biologist, Jakob von Uexküll
  • "So we have phytoplankton which are autotrophs, they are things that take in light and convert that into chemical energy, into glucose… if they are in the very surface waters, are in light intensities which are sufficient high, that the energy coming in from above from the Sun, is sufficiently energetic that they are unable to process all of the light that comes into them. And that energy will break down and convert into free radicals which are basically particles within the cell which have this effect of essentially sterilising the cell, they break down the DNA in the cell and kill the phytoplankton." – Dr Christopher Lowe, Lecturer in Marine Biology at Swansea University (speaking on BBC In Our Time episode on Plankton).

Alternative conceptions among learners can be encouraged by imprecise language when talking about energy. It is easy to slip into language with gives the impression energy can be created or destroyed. For example:

"…those moons are pulled and squeezed by the gravity of Jupiter, and that creates a friction which generates energy inside the moon, and that keeps the water warm and liquid."

Stuart Clark, astronomy journalist/author talking on the Guardian's 'Science Weekly' podcast.

Dr Clark's website reports that "The Independent placed him alongside Stephen Hawking and the Astronomer Royal, Professor Sir Martin Rees, as one of the 'stars' of British astrophysics teaching". To a layperson Dr Stuart Clark, FRAS, clearly seems to imply energy is created in this process (whereas a physicist or science teacher hearing this is likely to be so committed to the principle of conservation of energy that this possibility would probably not be noticed or suspected!) A few minutes later Dr Clark refers to how "this energy that is being put into the moon by the gravitational forces of Jupiter" suggesting transfer, rather than generation, of energy.

"The mitochondria are… little organelles in the cytoplasm of the cell, so not in the nucleus; and they are sometimes described as batteries, but that's a bit of an over-simplification because they both make, as well as store and release, the energy that the cell uses."

Professor Frances Flinter talking on an episode ('The war between science and religion') of BBC's 'Start the Week'

Professor Frances Flinter of St. Guy's & St Thomas' NHS Foundation Trust, Professor of Clinical Genetics at King's College, London, presumably did not literally mean that mitochondria could make energy, although this was the apparent message here.

Related conception:

Relativity shows that energy can be transformed into/out from matter

It is sometimes thought that Albert Einstein showed that energy is NOT always conserved, as his equation E=mc2 describes how much energy one gets by destroying a certain amount of matter. So, in beta decay for example, there is a 'mass defect' such that the rest mass of the proton and electron produced when the neutron decays is slightly less than that of the neutron. However, when the process is studied in detail it is found that both mass and energy are conserved in the process (when E=mc2 is used to find the identify the energy associated with different masses, and vice versa).

Again scientists may talk in ways that could mislead students on this:

Read about conceptions of mass defect

A confusing/confused topic

Writing about science in accessible – but also technically appropriate – ways can be quite challenging…

A buzz of energy

"It was in this laboratory that the Curies witnessed that while radium chloride looked like common salt in the daytime, it actually glowed in the dark. This effect was subsequently understood to be caused by its radiation agitating the nitrogen that is naturally present in the air. This vibration creates a buzz of energy, which is perceptible as a shimmer of light, just luminous enough to be visible in the dark."

Santos, 2020

Presumably this refers to emission of light when the molecules relax from an excited vibrational state to a lower energy vibrational state. No energy is 'created' of course.

Why is teaching and learning of science concepts so difficult: a brief overview

There are many possible ways of conceptualising natural phenomena and science topics. Arguably, we each have somewhat unique and idiosyncratic takes on scientific concepts, so there are always alternative conceptions which overlap and match to varying degrees.

Students often have intuitive ideas about the natural world, or have come across 'folk ideas', which are not consistent with scientific concepts. Some science teaching is regularly misunderstood so misconceptions circulate among students (and may even be found represented in text books).

Scientific theories may be sophisticated and nuanced, and so neither suitable for teaching novice learners nor (even with more advanced learners) for introducing in one step. Science curricula often have simplified and approximate representations of current scientific ideas ('curricula models') set out as target knowledge – so accounts at different levels are not entirely consistent.

Scientific ideas have developed over time, and have become more sophisticated and finely detailed. Many ideas once found useful in science have fallen into disuse either because it is now thought they were actually wrong, or they are no longer seen as helpful ways of thinking about a topic. Many of these ideas that are less developed, out of date, or now discredited, remain as 'conceptual fossils' that can be found in some science texts or more general literature and discourse.

Scientists develop models as thinking tools, often knowing the models are flawed: perhaps only giving approximate outcomes, or only being applicable in limited ranges of situations or they may be purely hypothetical (to be used to think through what would happen if…) without any expectation they reflect nature. Sometimes such models may appear in books to be of similar status to well founded principles laws and theories. Theories themselves vary in the extent to which they are considered to be likely correct, or just a provisional thinking tool.

Scientists, science communicators and journalists, and science teachers, use various techniques to help get a cross novel or abstract ideas: these can include analogies, similes, metaphors, narratives, and so forth. Sometimes these ideas get repeated and used so often they may seem to be part of the scientific idea, rather than just a linguistic tool. Indeed, sometimes terms originally used metaphorically become so widely adopted that they take on a new scientific meaning somewhat different form the original meaning.

Given all of that, it is not surprising that learning and teaching science can be quite challenging!

Work cited
  • Ali, T. (2015) Foreword, in Hubert Krivine, The Earth. From myths to knowledge. Versop, pp.vii-xi
  • Cassirer, Ernst (1950) The Problem of Knowledge. Philosophy, science, & history since Hegel. (Translat. William H. Woglom & Charles W. Hendel) New Haven & London: Yale University Press.
  • Feynman, Richard (1965) The Character of Physical Law, Cambridge, Massachusetts: M.I.T. Press.
  • Kuhn, T. S. (1978/1887) Black-Body Theory and the Quantum Discontinuity, 1894-1912. With a new afterword. The University of Chicago Press.
  • Santos, L. J. (2020) Half lives. The unlikely story of radium. Icon.
  • Taber, K. S. (2004) Intuitive physics: but whose intuition are we talking about?, Physics Education, 39 (2), pp.123-124.
Note:

1 It might seem that if Ernst Cassirer and Erst Mach were correct about the conservation of energy being intuitive, this should support student learning and help overcome learning difficulties (such as the very abstract nature of the energy concept.)

That would be a fair point, but we cannot assume that everyone has the same intuitions about the world (Taber, 2004)- and it may well be that those people whose intuitions better fit with the models and principles of physics are more likely to become scientists (and science teachers!)

Indeed, whilst conservation may seem a sensible intuition about the world, people may try to conserve the 'wrong' things form a scientific perspective. An example is the assumption (the conservation of force conception) that in an atom, the nucleus gives rise to a fixed amount of force which is shared out among the electrons present – so, if one is removed, the others experience a greater share of the force!

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