Category: imprecision of language

Misconceptions of change

It may be difficult to know what counts as an alternative conception in some topics – and sometimes research does not make it any clearer

Keith S. Taber

If a reader actually thought the researchers themselves held these alternative conceptions then one could have little confidence in their ability to distinguish between the scientific and alternative conceptions of others

I recently published an article here where I talked in some detail about some aspects of a study (Tarhan, Ayyıldız, Ogunc & Sesen, 2013) published in the journal Research in Science and Technological Education. Despite having a somewhat dodgy title 1, this is a well respected journal published by a serious publisher (Routledge/Taylor & Francis). I read the paper because I was interested in the pedagogy being discussed (jigsaw learning), but what promoted me to then write about it was the experimental design: setting up a comparison between a well-tested active learning approach and lecture-based teaching. A teacher experienced in active learning techniques taught a control group of twelve year old pupils through a 'traditional' teaching approach (giving the children notes, setting them questions…) as a comparison condition for a teaching approach based on engaging group-work.

The topic being studied by the sixth grade, elementary school, students was physical and chemical changes.

I did not discuss the outcomes of the study in that post as my focus there was on the study as possibly being an example of rhetorical research (i.e., a demonstration set up to produce a particular outcome, rather than an open-ended experiment to genuinely test a hypothesis), and I was concerned that the control conditions involved deliberately providing sub-optimal, indeed sub-standard, teaching to the learners assigned to the comparison condition.

Read 'Didactic control conditions. Another ethically questionable science education experiment?'

Identifying alternative conceptions

The researchers actually tested the outcome of their experiment in two ways (as well as asking students in the experimental condition about their perceptions of the lessons), a post-test taken by all students, and "ten-minute semi-structured individual interviews" with a sample of students from each condition.

Analysis of the post-test allowed the researchers to identify the presence of students' alternative conceptions ('misconceptions'2) related to chemical and physical change, and the identified conceptions are reported in the study. Interviewees were purposively selected,

"Ten-minute semi-structured individual interviews were carried out with seven students from the experimental group and 10 students from the control group to identify students' understanding of physical and chemical changes by acquiring more information about students' unclear responses to [the post-test]. Students were selected from those who gave incorrect, partially correct and no answers to the items in the test. During the interviews, researchers asked the students to explain the reasons for their answers to the items."

Tarhan et al., 2013, p.188

I was interested to read about the alternative conceptions they had found for several reasons:

  1. I have done research into student thinking, and have written a lot about alternative conceptions, so the general topic interests me;
  2. More specifically, it is interesting to compare what researchers find in different educational contexts, as this gives some insight into the origins and developments of such conceptions;
  3. Also, I think the 'chemical and physical changes' distinction is actually a very problematic topic to teach. (Read about a free classroom resource to explore learners' ideas about physical and chemical changes.)

In this post I am going to question whether the author's claims in their research report about some of the alternative conceptions they reported finding are convincing. First, however, I should explain the second point here.

Cultural variations in alternative conceptions

Some alternative conceptions seem fairly universal, being identified in populations all around the world. These may primarily be responses to common experiences of the natural world. An obvious example relates to Newton's first law (the law of inertia): we learn from very early experience, before we even have language to talk about our experiences, that objects that we push, throw, kick, toss, pull… soon come to a stop. They do not move off in a straight line and continue indefinitely at a constant speed.

Of course, that experience is not actually contrary to Newton's first law (as various forces are acting on the objects concerned), but it presents a consistent pattern (objects initially move off, but soon slow and stop) that becomes part of out intuitions about the world and so makes learning the scientific law seem counter-intuitive, and so more difficult to accept and apply when taught in school.

Read about the challenge of learning Newton's first law

By contrast, no one has ever tested Newton's first law directly by seeing what happens under the ideal conditions under which it would apply (see 'Poincaré, inertia, and a common misconception').

Other alternative conceptions may be less universal: some may be, partially at least, due to an aspect of local cultural context (e.g. folk knowledge, local traditions), the language of instruction, the curriculum or teaching scheme, or even a particular teacher's personal way of presenting material.

So, to the extent that there are some experiences that are universal for all humans, due to commonalities in the environment (e.g., to date at least, all members of the species have been born into an environment with a virtually constant gravitational field and a nitrogen-rich atmosphere of about 1 atmosphere pressure {i.e., c.105 Pa} and about 21% oxygen content), there is a tendency for people everywhere (on earth) to develop the same alternative conceptions.

And, conversely, to the extent that people in different institutional, social, and cultural contexts have contrasting experiences, we would expect some variations in the levels of incidence of some alternative conceptions across populations.

"Some common ideas elicited from children are spread, at least in part, through informal learning in everyday "life-world" contexts. Through such processes youngsters are inducted into the beliefs of their culture. Ideas that are common in a culture will not usually contradict everyday experience, but clearly beliefs may develop and be disseminated without matching formal scientific knowledge. …

Where life-world beliefs are relevant to school science – perhaps contradicting scientific principles, perhaps apparently offering an explanation of some science taught in school; perhaps appearing to provide familiar examples of taught principles – then it is quite possible, indeed likely, that such prior beliefs will interfere with the learning of school science. …

Different common beliefs will be found among different cultural groups, and therefore it is likely that the same scientific concepts will be interpreted differently among different cultural groups as they will be interpreted through different existing conceptual frameworks."

Taber, 2012a, pp.5-6

As a trivial example, in England the National Curriculum for primary age children in England erroneously describes some materials that are mixtures as being substances. These errors have persisted for some years as the government department does not think they are important enough to make the effort to correct the error. Assuming many primary school teachers (who are usually not science specialists, though some are of course) trust the flawed information in the official curriculum, we might expect more secondary school students in England, than in other comparable populations, to later demonstrate alternative conceptions in relation to the critical concept of a chemical substance.

"This suggests that studies from different contexts (e.g., different countries, different cultures, different languages of instruction, and different curriculum organisations) should be encouraged for what they can tell us about the relative importance of educational variables in encouraging, avoiding, overcoming, or redirecting various types of ideas students are known to develop."

Taber, 2012a, p.9
The centrality of language

Language of instruction may sometimes be important. Words that supposedly are translated from one language to another may actually have different nuances and associations. (In English, it is clearly an alternative conception to think the chemical elements still exist in a compound, but the meaning of the French élément chemie seems to include the 'essence' of an element that does continue into compound.)

Research in different educational contexts can in principle help unravel some of this: in principle as it does need the various researchers to detail aspects of the teaching contexts and cultural contexts from which they report as well as the student's ideas (Taber, 2012a).

Chemical and physical change

Teaching about chemical and physical change is a traditional topic in school science and chemistry courses. It is one of those dichotomies that is understandably introduced in simple terms, and so, offers a simplification that may need to be 'unlearnt' later:

[a change is] chemical change or physical change

[an element is] metal or non-metal

[a chemical bond is] ionic bonding or covalent bonding

There are some common distinctions often made to support this discrimination into two types of change:

Table 1.2 from Teaching Secondary Chemistry (2nd ed) (Taber, 2012b)

However, a little thought suggests that such criteria are not especially useful in supporting the school student making observations, and indeed some of these criteria simply do not stand up to close examination. 2

"the distinction between chemical and physical changes is a rather messy one, with no clear criteria to help students understand the difference"

Taber, 2012b, p.33


So, I was especially interested to know what Tarhan and colleagues had found.

Methodological 'small print'

In reading any study, a consideration of the findings has to be tempered by an understanding of how the data were collected and analysed. Writing-up research reports for journals can be especially challenging as referees and editors may well criticise missing details they feel should be reported, yet often journals impose word-limits on articles.

Currently (2023) this particular journal tells potential authors that "A typical paper for this journal should be between 7000 and 8000 words" which is a little more generous than some other journals. However, Tarhan and colleagues do not fully report all aspects of their study. This may in part be because they need quite a lot of space to describe the experimental teaching scheme (six different jigsaw learning activities).

Whatever the reason:

  • the authors do not provide a copy of the post-test which elicited the responses that were the basis of the identified alternative conceptions; and
  • nor do they explain how the analysis to identify conceptions was undertaken – to show how student responses were classified;
  • similarly, there are no quotations from the interview dialogue to illustrate how the researchers interpreted student comments .

Data analysis is the process of researchers interpreting data so they become evidence for their findings, and generally research journals expect the process to be detailed – but here the reader is simply told,

"Students' understanding of physical and chemical changes was identified according to the post-test and the individual interviews after the process."

Tarhan et al., 2013, p.189

'Misconceptions'

In their paper, Tarhan and colleagues use the term 'misconception' which is often considered a synonym for 'alternative conception'. Commonly, conceptions are referred to as alternative if they are judged to be inconsistent with canonical concepts.

Read about alternative conceptions

Although the term 'misconception' is used 32 times in the paper (not counting instances in the reference list), the term is not explained in the text, presumably because it is assumed that all those working in science education know (and agree) what it means. This is not at all unusual. I once wrote about another study

"[The] qualities of misconceptions are largely assumed by the author and are implicit in what is written…It could be argued that research reports of this type suggest the reported studies may themselves be under-theorised, as rather well-defined technical procedures are used to investigate foci that are themselves only vaguely characterised, and so the technical procedures are themselves largely operationalised without explicit rationale."

Taber, 2013, p.22

Unfortunately, in Tarhan and colleagues' study there are less well-defied technical procedures in relation to how data was analysed to identify 'misconceptions', so leaving the reader with limited grounds for confidence that what are reported are worthy of being described as student conceptions – and are not just errors or guesses made on the test. Our thinking is private, and never available directly to others, and, so, can only be interpreted from the presentations we make to represent our conceptions in a public (shared) space. Sometimes we mis-speak, or we mis-write (so that then our words do not accurately represent our thoughts). Sometimes our intended meanings may be misinterpreted (Taber, 2013).

Perhaps the researchers felt that this process of identifying conceptions from students' texts and utterances was unproblematic – perhaps the assignments seemed so obvious to the researchers that they did not need to exemplify and justify their analytical method. This is unfortunate. There might also be another factor here.

Lost and found in translation?

The study was carried out in Turkey. The paper is in English, and this includes the reported alternative conceptions. The study was carried out "in a public elementary school" (not an international school, for example). Although English is often taught as a foreign language in Turkish schools, the language of instruction, not unreasonably, is Turkish.

So, it seems either

  • the data was collected in (what, for the children, would have been) 'L2' – a second language, or
  • a study carried out (questions asked; answers given) in Turkish has been reported in English, translating where necessary from one language to another.

This issue is not discussed at all in the paper – there is no mention of either the Turkish or English language, nor of anything being translated.

Yet the authors are not oblivious to the significance of language issues in learning. They report how one variant of Jigsaw teaching had "been designed specifically to increase interaction among students of differing language proficiencies in bilingual classrooms" (p.186) and how the research literature reports that sometimes children's ideas reflect "the incorrect use of terms in everyday language" (p.198). However, they did not feel it was necessary to report either that

  1. data had been collected from elementary school children in a second language, or
  2. data had been translated for the purposes of reporting in an English language journal

It seems reasonable to assume they would have appreciated the importance of mentioning option 1, and so it seems much more likely (although readers of the study should not have to guess) the reporting in English involved translation. Yet translation is never a simple algorithmic process, but rather always a matter of interpretation (another stage in analysis), so it would be better if authors always acknowledged this – and offered some basis for readers to consider the translations made were of high quality (Taber, 2018).

Read about guidelines for detailing translation in research reports

It is a general principle that the research community should adopt, surely, that whenever material reported in a research paper has been translated from another language (a) this is reported and (b) evidence of the accuracy and reliability of the translation is offered (Taber, 2018).

I make this point here, as some of the alternative conceptions reported by the authors are a little mystifying, and this may(?) be because their wording has been 'degraded' (and obscured) by imperfect translation.

An alternative conception of combustion?

For example, here are two of the learning objectives from one of the learning activities:

"The students were expected to be able to:

…comment on whether the wood has similar intensive properties before and after combustion

…indicate the combustion reactions in examples of several physical and chemical changes"

Tarhan et al., 2013, p.193

The wording of the first of these examples seems to imply that when wood is burnt, the product is still…wood. That is nonsense, but possibly this is simply a mistranslation of something that made perfect sense in Turkish. (The problem is that a reader can only speculate on whether this is the case, and research reports should be precise and explicit.)

The second learning objective quoted here implies that some combustion reactions are physical changes (or, at least, combustion reactions are components of some physical changes).

Combustion reactions are a class of chemical reactions. 'Chemical reaction' is synonymous with 'chemical change'. So, there are (if you will excuse the double negative) no examples of combustion reactions that are not chemical reactions and which would be said to occur in physical changes. So, this is mystifying, as it is not at all clear what the children were actually being taught unless one assumes the researchers themselves have very serious misconceptions about the chemistry they are teaching.

If a reader actually thought that the researchers themselves held these alternative conceptions

  • the product of combustion of wood is still wood
  • some combustion reactions are (or occur as part of) physical changes

then one could have little confidence in their ability to distinguish between the scientific and alternative conceptions of others. (A reader might also ask how come the journal referees and editor did not ask for corrections here before publication – I certainly wondered about this).

There are other statements the authors make in describing the teaching which are not entirely clear (e.g., "give the order of the changes in matter during combustion reactions", p.194), and this suggests a degree of scepticism is needed in not simply accepting the reported alternative conceptions at face value. This does not negate their interest, but does undermine the paper's authority somewhat.

One of the misconceptions reported in the study is that some students thought that "there is a flame in all combustion reaction". This led me to reflect on whether I could think of any combustion reactions that did not involve a flame – and I must confess none readily came to mind. Perhaps I also have this alternative conception – but it seems a harsh judgement on elementary school learners unless they had actually been taught about combustion reactions without flames (if, indeed, there are such things).

The study reported that some 12 year olds held the 'misconception' that "there is a flame in all combustion reaction[s]".

[Image by Susanne Jutzeler, Schweiz, from Pixabay]

Failing to control variables?

Another objective was for students to "comprehend that temperature has an effect on chemical reaction rate by considering the decay of fruit at room temperature, and the change in color [colour] from green to yellow of fallen leaves in autumn" (p.193). As presented, this is somewhat obscure.

Presumably it is not meant to be a comparison between:

the rate of
decay of fruit at room temperature		andthe rate of
change in colour of fallen leaves in autumn
Explaining that temperature has an effect on chemical reaction rate?

Clearly, even if the change of colour of leaves takes place at a different temperature to room temperature, one cannot compare between totally different processes at different temperatures and draw any conclusions about how "temperature has an effect on chemical reaction rate" . (Presumably, 'control of variables' is taught in the Turkish science curriculum.)

So, one assumes these are two different examples…

But that does not help matters too much. The "decay of fruit at room temperature" (nor, indeed, any other process studied at a single temperature) cannot offer any indication of how "temperature has an effect on chemical reaction rate". The change of colours in leaves of deciduous trees (that usually begins before they fall) is triggered by environmental conditions such as change in day length and temperature. This is part of a very complex system involving a range of pigments, whilst water content of the leaf decreases (once the supply of water through the tree's vascular system is cut off), and it is not clear how much detail these twelve year olds were taught…but it is certainly not a simple matter of a reaction changing rate according to temperature.

Evaluating conceptions

Tarhan and colleagues report their identified alternative conceptions ('misconceptions') under a series of headings. These are reported in their table 4 (p.195). A reader certainly finds some of the entries in this table easy to interpret: they clearly seem to reflect ideas contrary to the canonical science one would expect to be reflected in the curriculum and teaching. Other statements are less obviously evidence of alternative conceptions as they do not immediately seem necessarily at odds with scientific accounts (e.g., associating combustion reactions with flames).

Other reported misconceptions are harder to evaluate. School science is in effect a set of models and representations of scientific accounts that often simplify the actual current state of scientific knowledge. Unless we know exactly what has been taught it is not entirely clear if students' ideas are credit-worthy or erroneous in the specific context of their curriculum.

Moreover, as the paper does not report the data and its analysis, but simply the outcome of the analysis, readers do not know on what basis judgements have been made to assign learners as having one of the listed misconceptions.


Changes of state are chemical changes

A few students from the lecture-based teaching condition were identified as 'having' the misconception that 'changes of state are chemical changes'. This seems a pretty serious error at the end of a teaching sequence on chemical and physical changes.

However, this raises a common issue in terms of reports of alternative conceptions – what exactly does it mean to say that a student has a conception that 'changes of state are chemical changes'? A conception is a feature of someone's thinking – but that encompasses a vast range of potential possibilities from a fleeting notion that is soon forgotten ('I wonder if s orbitals are so-called because they are spherical?') to an on-going commitment to an extensive framework of ideas that a life is lived by (Buddhism, Roman Catholicism, Liberalism, Hedonism, Marxism…).

A person's conceptions can vary along a range of characteristics (Figure from Taber, 2014)

The statement that 'Changes of state are chemical changes' is unlikely to be the basis of anyone's personal creed. It could simply be a confusion of terms. Perhaps a student had a decent understanding of the essential distinction between chemical and physical changes but got the terms mixed up (or was thinking that 'changes of state' meant 'chemical reaction'). That is certainty a serious error that needs correcting, but in terms of understanding of the science, would seem to be less worrying than a deeper conceptual problem.

In their commentary, the authors note of these children:

"They thought that if ice was heated up water formed, and if water was heated steam formed, so new matter was formed and chemical changes occurred".

Tarhan et al., 2013, p.197

It is not clear if this was an explanation the learners gave for thinking "changes of state are chemical changes", or whether "changes of state are chemical changes" was the researchers' gloss on children commenting that "if ice was heated up water formed, and if water was heated steam formed, so new matter was formed and chemical changes occurred".

That a range of students are said to have precisely the same train of thought leads a reader (or, at least, certainly one with experience of undertaking research of this kind) to ask if these are open-ended responses produced by the children, or the selection by the children of one of a number of options offered by the researchers (as pointed out above, the data analysis is not discussed in detail in the paper). That makes a difference in how much weight we might give to the prevalence of the response (putting a tick by the most likely looking option requires less commitment to, and appreciation of, an idea than setting it out yourself in your own personally composed text), illustrating why it is important that research journals should require researchers to give full accounts of their instrumentation and analysis.

Because density of matter changes during changes of state, its identity also changes, and so it is a chemical change

Thirteen of the children (all in the lecture-based teaching condition) were considered to have the conception "Because density of matter changes during changes of state, its identity also changes, and so it is a chemical change". This is clearly a much more specific conception (than 'changes of state are chemical changes') which can be analysed into three components:

  • a change of state is a chemical change, AND
  • we know this because such changes involve a change in identity, AND
  • we know that because a change of state leads to a change in density

Terhan and colleagues claim this conception was "first determined in this study" (p.195).

The specificity is intriguing here – if so many students explicitly and individually built this argument for themselves then this is an especially interesting finding. Unfortunately, the paper does not give enough detail of the methodology for a reader to know if this was the case. Again, if students were just agreeing with an argument offered as an option on the assessment instrument then it is of note, but less significant (as in such cases students might agree with the statement simply because one component resonated – or they may even be guessing rather than leaving an item unanswered). Again this does not completely negate the finding, but it leaves its status very unclear.

Taken together these first two claimed results seem inconsistent – as at least 13 students seem to think "Changes of state are chemical changes". That is, all those who thought that "Because density of matter changes during changes of state, its identity also changes, and so it is a chemical change" would seem to have thought that "Changes of state are chemical changes" (see the Venn diagram below). Yet, we are also told that only five students held the less specific and seemingly subsuming conception "changes of state are chemical changes".

If 13 students think that changes of state are chemical changes because a change of density implies a change of identity; what does it mean that only 5 students think that changes of state are chemical changes?

This looks like an error, but perhaps is just a lack of sufficient detail to make the findings clear. Alternatively, perhaps this indicates some failure in translating material accurately into English.

The changes in the pure matters are physical changes

Six children in the lecture-based teaching condition and one in the jigsaw learning condition were reported as holding the conception that "The changes in the pure matters are physical changes". The authors do not explain what they mean here by "pure matters" (sic, presumably 'matter'?). The only place this term is used in the paper is in relation to this conception (p.195, p.197).

The only other reference to 'pure' was in one of the learning objectives for the teaching:

  • explain the changes of state of water depending on temperature and pressure; give various examples for other pure substances (p.191)

If "pure matter" means a pure sample of a substance, then changes in pure substances are all physical – by definition a chemical changes leads to a different substance/different substances. That would explain why this conception was "first determined [as a misconception] in this study", p.195, as it is not actually a misconception)". So, it does not seem clear precisely why the researchers feel these children have got something wrong here. Again, perhaps this is a failure of translation rather than a failure in the original study?

Changes in shape?

Tarhan and colleagues report two conceptions under the subheading of 'changes in shape'. They seem to be thinking here more of grain size than shape as such. (Another translation issue?) One reported misconception is that if cube sugar is granulated, sugar particles become small [smaller?].

Is it really a misconception to think that "If cube sugar is granulated, sugar particles become small"?

(Image by Bruno /Germany from Pixabay)

Tarhan and colleagues reported that two children in the experimental condition, and 13 in the control condition thought that "If cube sugar is granulated, sugar particles become small". Sugar cubes are made of granules of sugar weakly joined together – they can easily be crumbled into the separate grains. The grains are clearly smaller than the cubes. So, what is important here is what is meant/understood* by the children by the term 'particles'.

(* If this phrasing was produced by the children, then we want to know what they meant by it. If, however, the children were agreeing with a phrase presented to them by researchers, then we wish to know how they understood it.)

If this means quanticle level particles, molecules, then it is clearly an alternative conception – each grain contain vast numbers of molecules, and the molecules are unchanged by the breaking up the cubes. If, however, particles here refers to the cube and grains**, then it is a fair reflection of what happens: one quite large particle of sugar is broken up into many much smaller particles. The ambiguity of the (English) word 'particles' in such contexts is well recognised.

(** That is, if the children used the word 'particles' – did they mean the cubes/grains as particles of sugar? If however the phrasing was produced by the researchers and presented to the children, and if the researchers meant 'particles' to mean 'molecules'; did the children appreciate that intention, or did they understand 'particles' to refer to the cubes and grains?)

However, as no detail is given on the actual data collected (e.g., is this the children's own words; was this based on an open response?), and how it was analysed (and, as I suspect this all occurred in Turkish) the reader has no way to check on this interpretation of the data.

What kind of change is dissolving?

Tarhan and colleagues report a number of 'misconceptions' under the heading of 'molecular solubility'. Two of these are:

  • "The solvation processes are always chemical changes"
  • "The solvation processes are always physical changes"

This reflects a problem of teaching about physical and chemical changes. Dissolving is normally seen as a physical change: there is no new chemical substance formed and dissolving is usually fairly readily reversed. However, as bonds are broken and formed it also has some resemblance to chemical change.2

In dissolving common salt in water, strong ionic bonds are disrupted and the ions are strongly solvated. Yet the usual convention is still to consider this a physical change – the original substance, the salt, can be readily recovered by evaporation of the solvent. A solution is considered a kind of mixture. In any case, as Tarhan and colleagues refer to 'molecular' solubility (strictly solubility refers to substances, not molecules, but still) they were, presumably, only dealing with examples of the dissolving of substances with discrete molecules.

Taking together these two conceptions, it seems that Tarhan and colleagues think that dissolving is sometimes a physical change, and sometimes a chemical change. Presumably they have some criterion or criteria to distinguish those examples of dissolving they consider physical changes from those they consider chemical changes. A reader can only speculate how a learner observing some solute dissolve in a solvent is expected to distinguish these cases. The researchers do not explain what was taught to the students, so it is difficult to appreciate quite what the students supposedly got wrong here.

Sugar is invisible in the water, because new matter is formed

The idea that learners think that new matter is formed on dissolving would indeed be an alternative conception. The canonical view is that new matter is only formed in very high energy processes – such as in the big bang. In both chemical and physical processes studied in the school laboratory there may be transformations of matter, but no new matter.

This seems a rather extreme 'misconception' for the learners to hold. However, a reader might wonder if the students actually suggested that a new substance was formed, and this has been mistranslated. (The Turkish word 'madde' seems to mean either matter or substance.) If these students thought that a new type of substance was formed then this would be an alternative conception (and it would be interesting to know why this led to sugar being invisible – unless they were simply arguing that different appearance implied different substance).

While sugar is dissolving in the water, water damages the structure of sugar and sugar splits off

Whether this is a genuine alternative conception or just imprecise use of language is not clear. It seems reasonable to suggest that while sugar is dissolving in the water, the process breaks up the structure of solid sugar and sugar molecules split off – so some more detail would be useful here. Again, if there has been translation from Turkish this may have lost some of the nuance of the original phrasing through translation into English.

The phrasing reflects an alternative conception that in chemical reactions one reactant is an active agent (here the water doing the damaging) and the other the patient, that is passive and acted upon (here the sugar being damaged) – rather than seeing the reaction as an interaction between two species (Taber & García Franco, 2010) – but there is no suggestion in their paper that this is the issue Tarhan and colleagues are highlighting here.

When sugar dissolves in water, it reacts with water and disappears from sight

If the children thought that dissolving was a chemical reaction then this is an alternative conception – the sugar does indeed disappear from sight, but there has been no reaction.

Again, we might ask if this was actually a misunderstanding (misconception), or imprecise use of language. The sugar does 'react' with the water in the everyday sense of 'reaction'. But this is not a chemical reaction, so this terminology should be avoided in this context.

Even in science, 'reaction' means something different in chemistry and physics: in the sense of Newtonian physics, during dissolving, when a water molecule attracts a sugar molecule {'action')'} there will be an equal and oppositely directed reaction as the sugar molecule attracts the water molecule. This is Newton's third law, which applies to quanticles as much as to planets. If a water molecule and a sugar molecule collide, the force applied by the sugar molecule on the water molecule is equal to the force applied by the water molecule on the sugar molecule.

Read about learning difficulties with Newton's third law

So, 'sugar reacts with water' could be

  • a misunderstanding of dissolving (a genuine alternative conception);
  • a misuse of the chemical term 'reaction'; or
  • a use of the everyday term 'reaction' in a context where this should be avoided as it can be misunderstood

These are somewhat different problems for a teacher to address.

Molecules split off in physical changes and atoms split off in chemical changes

Ten of the children are said to have demonstrated the 'misconception' that molecules split off in physical changes and atoms split off in chemical changes. The authors claim that this misconception has not been reported in previous studies. But is this really a misconception? It may be a simplistic, and imprecise, statement – but I think when I was teaching youngsters of this age I would have been happy to find they have this notion – which at least seems to reflect an ability to imagine and visualise processes at the molecular level.

In dissolving or melting/boiling of simple molecular substances, molecules do indeed 'split off' in a sense, and in at least some chemical changes we can posit mechanisms that, in simple terms at least, involve atoms 'splitting off' from molecules.

So, again, this is another example of how this study is tantalising, without being very informative. The reader is not clear in what sense this is viewed as wrong, or how the conception was detected. (Again, for ten different students to specifically think that 'molecules split off in physical changes and atoms split off in chemical changes' makes one wonder if they volunteered this, or have simply agreed with the statement when having it presented to them).

In conclusion

The main thrust of Tarhan and colleagues' study was to report on an innovation using jig-saw learning (which unfortunately compared this with a form of pedagogy widely considered unsuitable for young children, so offering a limited basis for judging effectiveness of the innovation). As part of the study they collected data to evaluate learning in the two conditions, and used this to identify misconceptions students demonstrated after being taught about physical and chemical changes. The researchers provide a long list of identified misconceptions – but it is not always obvious why these are considered misconceptions, and what the desired responses matching teaching models were.

The researchers do not detail their data collection and analysis instruments and protocols in sufficient detail for a readers to appreciate what they mean by their results. In particular, what it means to have a misconception – e.g., to give a definitive statement in an interview, or just to select some response on a test as the answer that looked most promising at the time. Clearly we give much more weight to a notion that a learner presents in their own words as an explanation for some phenomenon, than the selection of one option from a menu of statements presented to them that comes with no indication of their confidence in the selection made.

Of particular concern: either the children were asked questions in a second language that they may not have been sufficiently fluent in to fully understand questions or compose clear responses; or none of the misconceptions reported are presented in their original form and they have all been translated by someone (unspecified) of uncertain ability as a translator. (A suitably qualified translator would need to have high competence in both languages and a strong familiarity with the subject matter being translated.)

In the circumstances, Tarhan and colleagues' reported misconceptions are little more than intriguing. In science, the outcome of a study is only informative in the context of understanding exactly how the data were obtained, and how they have been processed. Without that, readers are asked to take a researcher's conclusions on faith, rather than be persuaded of them by a logical chain of argument.

p.s. For anyone who did not know, but wondered: s orbitals are not so-called because they are spherical: the designation derives from a label ('sharp') that was applied to some lines in atomic spectra.

Work cited
Notes

1 To my reading, the publication title 'Research in Science and Technological Education' seems to suggest the journal has two distinct and somewhat disconnected foci, that is:

Research in ( Science ) and ( Technological Education )

And it would be better (that is, most consistently) titled as

Research in Science and Technology Education

{Research in ( Science and Technology ) Education}

or

Research in Scientific and Technological Education

{Research in ( Scientific and Technological ) Education}

but, hey, I know I am pedantic.

2 The table (Table 1.2 in the source) was followed by the following text:

"The first criterion listed is the most fundamental and is generally clear cut as long as the substances present before and after the change are known. If a new substance has been produced, it will almost certainly have different melting and boiling temperatures than the original substance.

The other [criteria] are much more dubious. Some chemical changes involve a great deal of energy being released, such as the example of burning magnesium in air, or even require a considerable energy input, such as the example of the electrolysis of water. However, other reactions may not obviously involve large energy transfers, for example when the enthalpy and entropy changes more or less cancel each other out…. The rusting of iron is a chemical reaction, but usually occurs so slowly that it is not apparent whether the process involves much energy transfer ….

Generally speaking, physical changes are more readily reversible than chemical changes. However, again this is not a very definitive criterion. The idea that chemical reactions tend to either 'go' or not is a useful approximation, but there are many examples of reactions that can be readily reversed…. In principle, all reactions involve equilibria of forward and reverse reactions, and can be reversed by changing the conditions sufficiently. When hydrogen and oxygen are exploded, it takes a pedant to claim that there is also a process of water molecules being converted into oxygen and hydrogen molecules as the reaction proceeds, which means the reaction will continue for ever. Technically such a claim may be true, but for all practical purposes the explosion reflects a reaction that very quickly goes to completion.

One technique that can be used to separate iodine from sand is to warm the mixture gently in an evaporating basin, over which is placed an upturned beaker or funnel. The iodine will sublime – turn to vapour – before recondensing on the cold glass, separated from the sand. The same technique may be used if ammonium chloride is mixed with the sand. In both cases the separation is achieved because sand (which has a high melting temperature) is mixed with another substance in the solid state that is readily changed into a vapour by warming, and then readily recovered as a solid sample when the vapour is in contact with a colder surface. There are then reversible changes involved in both cases:

solid iodine ➝ iodine vapour

ammonium chloride ➝ ammonia + hydrogen chloride

In the first case, the process involves only changes of state: evaporation and condensation – collectively called sublimation. However the second case involves one substance (a salt) changing to two other substances. To a student seeing these changes demonstrated, there would be little basis to infer one is (usually considered as) a chemical change, but not the other. …

The final criterion in Table 1.2 concerns whether bonds are broken and made during a change, and this can only be meaningful for students once they have learnt about particle models of the submicroscopic structure of matter… In a chemical change, there will be the breaking of bonds that hold together the reactants and the formation of new bonds in the products. However, we have to be careful here what we mean by 'bond' …

When ice melts and water boils, 'intermolecular' forces between molecules are disrupted and this includes the breaking of hydrogen 'bonds'. However, when people talk about bond breaking in the context of chemical and physical changes, they tend to mean strong chemical bonds such as covalent, ionic and metallic bonds…

Yet even this is not clear cut. When metals evaporate or are boiled, metallic bonds are broken, although the vapour is not normally considered a different substance. When elements such as carbon and phosphorus undergo phase changes relating to allotropy, there is breaking, and forming, of bonds, which might suggest these changes are chemical and that the different forms of the same elements should be considered different substances. …

A particularly tricky case occurs when we dissolve materials to form solutions, especially materials with ionic bonding…. Dissolving tends to involve small energy changes, and to be readily reversible, and is generally considered a physical change. However, to dissolve an ionic compound such as sodium chloride (table salt), the strong ionic bonds between the sodium and chloride ions have to be overcome (and new bonds must form between the ions and solvent molecules). This would seem to suggest that dissolving can be a chemical change according to the criterion of bond breaking and formation (Table 1.2)."

(Taber, 2012b, pp.31-33)

Temperature is measuring the heat of something …

Keith S. Taber

Image by Peter Janssen from Pixabay 

Bill was a participant in the Understanding Science Project. Bill, then in Y7, was telling me about work he had done in his science class on the states of matter, and what happened to the particles that made up objects during a change of state. He suggested that "when a solid goes to a liquid, the heat gives the particles energy to spread about, and then when its a liquid, it's got even more energy to spread out into a gas". Later in the interview I followed up to find out what Bill understood by heat:

Now you mentioned earlier, something about heat. When you were talking about the experiment you did.

Yeah.

Yeah. So tell me about the heat again, what's, how does the heat get involved in this solids, liquids and gases?

When I heat, when heat comes to a solid, it will have, erm, a point where it will go down to a liquid,

Okay,

A melting points of the, the object.

Do you know what heat is? If you had a younger brother or sister, and they said to you, 'you are good at science, what's heat?'

I'm not sure how I can explain it, 'cause it's, it can be measured at different temperature, it can be measured at temperature, erm, by degrees Celsius, degrees Fahrenheit, and – I'm not really sure how I could explain what it is, but, I know it can be measured and changed.

So is it the same thing as temperature, do you think, or is it something different?

Erm, I think temperature is measuring the heat of something.

So they're related, they're to do with each other?

Yeah.

But they are not exactly the same?

No.

Bill appreciated that heat and temperature were not the same, but was not entirely clear on the relationship. Distinguishing between heat and temperature is a recognised challenge in teaching and learning physics.

We commonly introduce temperature as a measure of how hot or cold something is – which relates to phenomena that all students have experienced (even if our actual perception of temperature is pretty crude). Heating is a process, and heat is sometimes considered to be energy being transferred due to a difference of temperature (although energy is a very abstract notion and there is much discussion in science teaching circles about the best language to be used in teaching about energy).

Put simply, it is reasonable to suggest a very hot object would have a high temperature, but not that it contained a lot of heat. So, it is strictly wrong to say that "temperature is measuring the heat of something" (and it would be more correct, if not very technical, to say instead "temperature is measuring the hotness of something – how hot something is"). Perhaps the idea Bill wanted to express was more about the heat that one can feel radiating form a hot object (but likely that is an interpretation suggested by the canonical science use of 'heat'?)

This is one of those situations where a student has an intuition or idea which is basically along the right lines, in the sense of knowing there is an association or link, but strictly not quite right – so, an alternative conception. In a teaching situation it might be useful to know if a student actually has a firm conception that temperature measures the amount of heat, or (as seems to be the case with Bill) this is more a matter of using everyday language – which tends to be less precise and rigid than technical language – to express a vague sense. If a student has a firm notion that hot objects contain heat, and this is not identified and responded to, then this could act as a grounded learning impediment as it will likely distort how teaching is understood.

The teacher is charged with shifting learners away from their current ways of thinking and talking, towards using the abstractions and technical language of the subject, such as the canonical relationship between heat and temperature – and this often means beginning by engaging with the learners' ideas and language. Arguably the use of the term 'heat capacity' (and 'specific heat capacity') which might suggest something about the amount of heat something can hold, is unhelpful here.

.

The nucleus is the brain of the cell

Keith S. Taber

Brain Image by b0red from Pixabay; cell image by Clker-Free-Vector-Images from Pixabay

…but is it the same as an atomic nucleus?

Bert was a participant in the Understanding Science Project. Bert was interviewed in Y10 and asked about the topics he had been studying, which included circulation in biology, static electricity in physics, and oxidation in chemistry. He had talked about protons, electrons and atoms in both chemistry (studying atomic structure) and physics (studying static electricity), and was asked if this could also link with biology:

Do you think there are any links with Biology?

Yeah, well there are lots of atoms in you. And we did about the nucleus which we've been doing about in Biology. I'm not sure if there's a link between it, but.

Ah, that's interesting, so

'cause we did about plant and animal cells in Biology, so it's got a nucleus….as I was saying about the blood cells and things. We were doing about the animal and plant cells and, you know, we were seeing what's the same between them and what's different.

So a connection between physics and chemistry on one hand, and biology on the other, was that cells also had a nucleus. This is a term used across these three sciences, but of course the concepts of atomic and cellular nuclei are quite distinct. Was that clear to Bert? What did he understand about cellular nuclei?

So what's the nucleus then?

It's kind of like erm, the brain of the cell kind of. It's, it's what gets the cell to do everything, it's like, the core of the cell.

This response is interesting because, at one level, it suggests that Bert did not have a detailed and well-focussed 'off pat' answer. However, that may not be such a bad thing – definitions that are learnt 'off by heart' may only represent rote learning and may not be well understood. Indeed, it has been argued (in the work of Thomas Kuhn, for example) that in learning science a technical definition is often only really useful once the concept has been acquired: that is once the meaning of the word being defined has, to some degree, already been grasped.

At another level, Bert's answer could be seen as quite sophisticated. What could be taken as an ambiguous response, a difficulty in finding the words to represent his thinking, could also be seen as multifaceted:

  • essential: the nucleus is the brain of the cell
  • functional: the nucleus controls the cell (it's what gets the cell to do everything)
  • structural: the nucleus is the core of the cell

That is, Bert's response could be read, not as a series of alternative suggestions and self-corrections, but rather as a set of complementary images or 'faces' of a complex idea. That would fit with a notion of concepts as being nodes in conceptual networks where the meaning of a particular concept depends upon the way it is associated with others.

(Read about 'Concepts')

The suggestion that the brain reference is intended to be about the essential nature of the nucleus is of course a reading of the text that must be seen as a speculative interpretation. (It probably does not even make sense to ask if Bert intended it this way, as in conversation much of our dialogue does not await deliberation, but is spontaneous, relying largely on implicit cognition.) But, as a teacher, I can see this as a kind of pedagogic device along the lines: 'you ask we what the nucleus is, let me compare it with something you will be familiar with, in essence it is like the brain of the cell'.

This is clearly meant metaphorically ("kind of like erm, the brain of the cell kind of"): that is, it is assumed that the person hearing the metaphor can make the expected sense of the comparison. Metaphors have an essential (sic) role in teaching and in communication more generally, though like other such 'figures' of speech (simile, analogy, anthropomorphism, animism), may become habitually used in place of the deeper meaning they are meant to introduce (Taber & watts, 1996).

(Read about 'metaphor in science')

…

It's kind of like erm, the brain of the cell kind of. It's, it's what gets the cell to do everything, it's like, the core of the cell.

Okay. And why is there a connection with Chemistry or the Physics then?

Because erm, we were doing, we were doing in Chemistry about the nucleus has the – neutrons and the protons in the nucleus, then around it is a field of electrons.

…So why is that a connection then? Why is that a connection between the Biology and the Chemistry and the Physics?

Well it's just the nucleus comes under both of them.

Comes under both of them. So is it the same thing?

I wouldn't have thought so, but because when I think of electrons and neutrons I think of electricity, which I don't really think of in our, in our bodies but it could be perhaps. We haven't been told about that.

So there is ambiguity in Bert's report: the nucleus comes up in chemistry and physics in the context of atoms, and in biology in the context of cells. Although the term is the same, so there is at least that connection, Bert "wouldn't have thought" it was the same thing in these different contexts (after all, he would not expect there to be electricity in our bodies!) …but, then again, "it could be perhaps", as they had not been told otherwise. (A possible subtext here being: surely the teacher(s) would have pointed out this was something different if they were going to use the same word for two different things in science lessons?)

The use of the same word label, nucleus, for the rather differently natured nuclei in atoms and cells has potential to act as a linguistic learning impediment (a form of associative learning impediment) as one meaning will likely already be established when a learner meets the other use of the word. It perhaps makes matters worse that part of the meaning, the central component (the structural 'face' of the concept), is the same, than had the usage been clearly unrelated (as in 'bank' being a financial institution and the structure at the edge of a rvier such that the context of use make confusion unlikely). Not only that, but for Bert, these were components of similarly "really microscopic" entities (see 'The cell nucleus is "probably" bigger than an atomic nucleus').

From the perspective of the science teacher, there is little basis for confusing the nucleus of an atom with that of a cell: obviously a cell is a complex entity with a great many components, each of which has itself a complex supra-molecular structure – so clearly the atomic nucleus is on a scale many orders of magnitude smaller than a cell nucleus. However, the expert perspective is based on relating a lot of knowledge that the novice may not yet have, or at least, may not yet be coordinating. In Bert's case, he was only just starting to coordinate these ideas (see 'The cell nucleus is "probably" bigger than an atomic nucleus').

Source cited:

Sleep can give us energy

Sleep, like food, can give us a bit more energy

Keith S. Taber

Image by Daniela Dimitrova from Pixabay 

Jim was a participant in the Understanding Science Project. When I was talking to students on that project I would ask them what they were studying in science, rather than ask them about my own agenda of topics. However, I was interested in the extent to which they integrated and linked their science knowledge, so I would from time to time ask if topics they told me about were linked with other topics they had discussed with me. The following extract is taken from the fourth of a sequence of interviews during Jim's first year in secondary school (Y7 in the English school system).

And earlier in the year, you were doing about dissolving sugar. Do you remember that?

Erm, yeah.

Do you think that's got anything to do with the human body?

Erm, we eat sugar.

Mm. True.

Gives us energy…It powers us.

Ah. And why do we need power do you think?

So we can move.

This seemed a reasonable response, but I was intrigued to know if Jim was yet aware of metabolism and how the tissues require a supply of sugar even when there is no obvious activity.

Ah what if you were a lazy person, say you were a very lazy rich person? And you were able to lie in bed all day, watch telly, whatever you like, didn't have to move, didn't have to budge an eyelid, … you're rich, your servants do everything for you? Would you till need energy?

Yes.

Why?

I dunno, 'cause being in bed's tired, tiring.

Is it?

When I'm ill, I stay off for a day, I just feel tired, and like at the end of the day, even more tired than I do when I come to school some times.

Jim's argument failed to allow for the difference in initial conditions

Staying in bed all day and avoiding exercise could indeed make one feel tired, but there seemed something of a confound here (being ill) and I wondered if the reason he stayed in bed on these days might be a factor in feeling even more tired than usual.

So maybe when you are ill, you should come to school, and then you would feel better?

No.

No, it doesn't work like that?

No.

Okay, so why do you think we get tired, when we are just lying, doing absolutely nothing?

Because, it's using a lot of our energy, doing something.

Hm, so even when we are lying at home ill, not doing anything, somehow we are using energy doing something, are we?

Yes.

What might that be, what might we use energy for?

Thinking.

I thought this was a good response, as I was not sure all students of his age would realise that thinking involved energy – although my own conceptualisation was in terms of cellular metabolism, and how thinking depend on transmitting electrical signals along axons and across synapses. I suspected Jim might not have been thinking in such terms.

Do you think it uses energy to think?

(Pause, c.3s)

Probably.

Why do you think that?

Well cause, like, when you haven't got any energy, you can't think, like the same as TV, when it hasn't got any energy, it can't work. So it's a bit like our brains, when we have not got enough energy we feel really tired, and we just want to go to sleep, which can give us more energy, a bit like food.

So Jim here offered an argument about cause and effect- when you haven't got any energy, you can't think. This would certainly be literally true (without any source of energy, no biological functioning would continue, including thinking) although of course Jim had clearly never experienced that absolute situation (as he was still alive to be interviewed), and was presumably referring to experiences of feeling mentally tired and not being able to concentrate.

He offered an analogy, that we are like televisions, in that we do not work without energy. The TV needs to be connected to an electrical supply, and the body needs food (such as sugar, as Jim had suggested) and oxygen. But Jim also used a simile – that sleep was like food. Sleep, like food, according to Jim could give us energy.

So sleeping can give us energy?

Yeah.

How does that work?

Er, it's like putting a battery onto charge, probably, you go to sleep, and then you don't have to do anything, for a little while, and you, then you wake up and you feel – less tired.

Okay so, you think you might need energy to think, because if you have not got any energy, you are very tired, you can't think very well, but somehow if you have a sleep, that might somehow bring the energy back?

Yeah.

So where does that energy come from?

(Pause c.2s)

Erm – dunno.

So here Jim used another analogy, sleeping was like charging a battery. When putting a battery on change, we connect it to a charger, but Jim did not suggest how sleep recharged us, except in that we could rest. When sleeping "you don't have to do anything, for a little while", which might explain a pause in depletion of energy supplies, but would not explain how energy levels were built up again.

[A potentially useful comparison here might have been a television, or a lap top used to watch programmes, with an internal battery, where the there is a buffer between the external supply, and the immediate source for functioning.]

This was an interesting response. At one level it was a deficient answer, as energy is conserved, and Jim's suggestion seemed to require energy to be created or to appear from some unspecified source.

Jim's responses here offered a number of interesting comparisons:

  • sleep is a bit like food in providing energy
  • not having energy and not being able to think is like a TV which cannot work without energy
  • sleeping is like putting a battery on charge

Both science, and science teaching/communication draw a good deal on similes, metaphors and analogies, but they tend to function as interim tools (sources of creative ideas that scientists can then further explore; or means to help someone get a {metaphorical!} foothold on an idea that needs to later be more formally understood).

The idea that sleeping works like recharging a battery could act as an associative learning impediment as there is a flaw in the analogy: putting a battery on charge connects it to an external power source; sleep is incredibility important for various (energy requiring) processes that maintain physical and mental health, and helps us feel rested, but does not in itself source energy. Someone who thought that sleeping works like recharging a battery will not need to wonder how the body accesses energy during sleep as they they seem to have an explanation. (They have access to a pseudo-explanation: sleep restores our energy levels because it is like recharging a battery.)

Jim's discourse reflects what has been called 'the natural attitude' or the 'lifeworld', the way we understand common experiences and talk about them in everyday life. It is common folk knowledge that resting gives you energy (indeed, both exercise and rest are commonly said to give people energy!)

In 'the lifeworld', we run out of energy, we recharge our batteries by resting, and sleep gives us energy. Probably even many science teachers use such expressions when off duty. Each of these notions is strictly incorrect from the scientific perspective. A belief that sleep gives you energy would be an alternative conception, and one that could act as a grounded learning impediment, getting in the way of learning the scientific account.

Yet they each also offer a potential entry point to understanding the scientific accounts. In one respect, Jim has useful 'resources' that can be built on to learn about metabolism, as long as the habitual use of technically incorrect, but common everyday, ways of talking do not act as learning impediments by making it difficult to appreciate how the science teacher is using similar language to express a somewhat different set of ideas.

How plants get their food to grow and make energy

Respiration produces energy, but photosynthesis produces glucose which produces energy

Keith S. Taber

Image by Frauke Riether from Pixabay 

Mandy was a participant in the Understanding Science Project. When I spoke to her in Y10 (i.e. when she was c.14 year old) she told me that photosynthesis was one of the topics she was studying in science. So I asked her about photosynthesis:

So, photosynthesis. If I knew nothing at all about photosynthesis, how would you explain that to me?

It's how plants get their food to grow and – stuff, and make energy

So how do they make their energy, then?

Well, they make glucose, which has energy in it.

How does the energy get in the glucose?

Erm, I don't know.

It's just there is it?

Yeah, it's just stored energy

I was particularly interested to see if Mandy understood about the role of photosynthesis in plant nutrition and energy metabolism.

Why do you think it is called photosynthesis, because that's a kind of complicated name?

Isn't photo, something to do with light, and they use light to – get the energy.

So how do they do that then?

In the plant they've got chlorophyll which absorbs the light, hm, that sort of thing.

What does it do once it absorbs the light?

Erm.

Does that mean it shines brightly?

No, I , erm – I don't know

Mandy explained that the chlorophyll was in the cells, especially in the plant's leaves. But I was not very clear on whether she had a good understanding of photosynthesis in terms of energy.

Do you make your food?

Not the way plants do.

…

So where does the energy come from in your food then?

It's stored energy.

How did it get in to the food? How was it stored there?

Erm.

[c. 2s pause]

I don't know.

At this point it seemed Mandy was not connecting the energy 'in' food either directly or indirectly with photosynthesis.

Okay. What kind of thing do you like to eat?

Erm, pasta.

Do you think there is any energy value in pasta? Any energy stored in the pasta?

Has lots of carbohydrates, which is energy.

…

So do you think there is energy within the carbohydrate then?

Yeah.

Stored energy.

Yeah.

So how do you think that got there, who stored it?

(laughs) I don't know.

Again, the impression was that Mandy was not linking the energy value of food with photosynthesis. The reference to carbohydrates being energy seemed (given the wider context of the interview) to be imprecise use of language, rather than a genuine alternative conception.

So do you go to like the Co-op and buy a packet of pasta. Or mum does I expect?

Yeah.

Yeah. So do you think, sort of, the Co-op are sort of putting energy in the other end, before they send it down to the shop?

No, it comes from 'cause pasta's made from like flour, and that comes from wheat, and then that uses photosynthesis.

Now it seemed that it was quite clear to Mandy that photosynthesis was responsible for the energy stored in the pasta. It was not clear why she had not suggested this before, but it seemed she could make the connection between the food people eat and photosynthesis. Perhaps (it seems quite likely) she had previously been aware of this and it initially did not 'come to mind', and then at some point during this sequences of questions there was a 'bringing to mind' of the link. Alternatively, it may have been a new insight reached when challenged to respond to the interview questions.

So you don't need to photosynthesise to get energy?

No.

No, how do you get your energy then?

We respire.

Is that different then?

Yeah.

So what's respire then, what do you do when you respire?

We use oxygen to, and glucose to release energy.

Do plants respire?

Yes.

So when do you respire, when you are going to go for a run or something, is that when you respire, when you need the energy?

No, you are respiring all the time.

Mandy suggested that plants mainly respire at night because they are photosynthesising during the day. (Read 'Plants mainly respire at night'.)

So is there any relationship do you think between photosynthesis and respiration?

Erm respiration uses oxygen – and glucose and it produces er carbon dioxide and water, whereas photosynthesis uses carbon dioxide and water, and produces oxygen and glucose.

So it's quite a, quite a strong relationship then?

Yeah.

Yeah, and did you say that energy was involved in that somewhere?

Yeah, in respiration, they produce energy.

What about in photosynthesis, does that produce energy?

That produces glucose, which produces the energy.

I see, so there is no energy involved in the photosynthesis equation, but there is in the glucose?

Yeah.

Respiration does not 'produce' energy of course, but if it had the question about whether photosynthesis also produced energy might have been expected to elicit a response about photosynthesis 'using' energy or something similar, to give the kind of symmetry that would be consistent with conservation of energy (a process and its reverse can not both 'produce' energy). 'Produce' energy might have meant 'release' energy in which case it might be expected the reverse process should 'capture' or 'store' it.

Mandy appreciated the relationship between photosynthetic and respiration in terms of substances, but had an asymmetric notion of how energy was involved.

Mandy appeared to be having difficult appreciating the symmetrical arrangement between photosynthesis and respiration because she was not clear how energy was transformed in photosynthesis and respiration. Although she seemed to have the components of the scientific narrative, she did not seem to fully appreciate how the absorption of light was in effect 'capturing' energy that could be 'stored' in glucose till needed. At this stage in her learning she seemed to have grasped quite a lot of the relevant ideas, but not quite integrated them all coherently.