Understanding students' intuitions about the world could provide insight into their misconceptions of chemical concepts

In Short
  • Students' intuitive understanding of chemical concepts can be at odds with what teachers are trying to explain in class
  • Identifying students' intuitions can help teachers build on these and teach more effectively   

Do students come to chemistry lessons with strong intuitions about the world that could determine how they make sense of chemistry teaching? Do learners have 'prior expectations' about the abstract molecular realm? The answers to such questions could provide insight into addressing students' misconceptions of chemical phenomena.  

Research has identified aspects of the way students think about scientific phenomena, often in terms of misconceptions1 or 'alternative frameworks',2 that interfere with learning science presented in the curriculum. For example, it is common for students to equate melting with dissolving, or to assume that compounds will share the properties of the elements that they 'contain'. The particles that chemists use to explain chemical structures and reactions are often considered to share macroscopic properties (such as crystal shape or melting point), and to be surrounded by air or some other substance. Teachers are warned to look out for and even to challenge such thinking in their own classes. If we could understand how and why it is that in some topics students tend to adopt ways of thinking at odds with the science they are taught then teachers might be able to 'head off' some of these alternative conceptions before students take them up.  

Pattern recognition and perception

Most of us are familiar with the ambiguous figures that are sometimes found in collections of 'optical illusions' such as the silhouette that could be a duck - or a rabbit. Other figures may seem to show meaningless patterns, until in a flash of insight we recognise the latent image, which then becomes obvious and difficult to see past. Thus the human brain works as a very powerful pattern matching system and when messages are unclear, our brains do their best to select and present to our conscious minds the most likely option.

Figure 1 - Can you see a face in this photo?

Figure 1 - Can you see a face in this photo?

We also over-interpret patterns, for example when faces are 'seen' in the most unlikely places, such as the man 'in the Moon'. Most readers will initially see nothing unusual in Fig 1, a photo of the Norfolk coast. But once you do spot the 'face' in the clouds, it then becomes hard 'not to see'. The way new-born infants respond to faces, and simple face-like patterns, strongly suggests that some of our pattern-recognition systems are innate, hard-wired into our brains through having been selected in evolution.

For most of the period humans have been evolving, they have not been having formal schooling in chemistry, and so what pattern-recognition systems we have are not fine-tuned to recognising the Periodical Table, multiplets on an nmr spectrum, or the structural formulae of steroids.  

Physics educators have long suggested that by the time children start school they have developed 'intuitive physics'. They have already learnt to recognise many aspects of the physical world as fitting basic patterns that seem to recur. Researchers call these basic patterns 'phenomenological primitives', or p-prims. One common pattern is that action is produced by some kind of 'agent', acting on an 'object' with an 'instrument'. An example is an ice hockey player hitting a puck with a stick. The research suggests, however, that, as with non-existent faces in the clouds, the brain tends to spot this pattern even when it is not appropriate. As this is an intuitive process, acting at an unconscious level, it is insidious. We can decide there is no giant lurking in the clouds, but we still see its face. 

Unfortunately for science teachers, some of these physical intuitions prove to be inconsistent with the physics of inertia (bodies keep moving unless impeded), circular motion (not 'natural' motion, but a form of accelerated motion requiring centripetal force) and action-reaction (a small body exerts as big a force on a large body as it is itself subject to). A good deal of effort in teaching physics is spent attempting to shift student thinking from the way 'common sense' construes the world, to the way formal physics describes and explains it.  

At first sight, we might expect chemistry to suffer less from this problem. After all physics is often about such familiar phenomena as balls being rolled or projected etc and physics may be explained in terms of skateboards or racing cars - contexts where learners already have developed their intuitions of what is going on. Much of chemistry, however, is explained in terms of molecules and ions, of electrons and orbitals. Since these are theoretical entities beyond normal experience, students are not likely to start school already having notions about stable electronic configurations, or variable oxidation states. 

Yet it is clear that, just as in physics, students demonstrate many 'misconceptions' in chemistry, and may even develop extensive alternative conceptual frameworks at odds with the chemistry in the curriculum.5 This is actually what the p-prim theory would predict. So even when studying totally unfamiliar chemical concepts, learners are subject to intuitive mechanisms interpreting our teaching in terms of these archetypal patterns.  

Making sense of student ideas

This theory may suggest why sometimes even the most careful chemistry teaching is often misinterpreted by students, but it could also offer clues on how to teach chemistry to take advantage of the cognitive mechanisms at work.

Some examples of students' misconceptions that have been reported are certainly suggestive of a mechanism of this type taking place. So, for example, students readily take up the notion that full electron shells offer stability, and use this principle far beyond its valid range of application. This might well link to a more basic intuition about the relative structural integrity of things that are full and complete compared with those that are unfinished or broken. Sixthform students commonly consider that when an electron is removed from the atom, its 'share' of the nuclear attraction is reallocated. While this is poor chemistry, it reflects a notion of 'sharing-out' that is commonly found in everyday situations. Perhaps students do come to chemistry lessons with intuitive mechanisms that map what they are taught onto such existing expectations about the way the world works. If students do indeed share a set of common p-prims that mediate all they see and hear, then identifying these fundamental patterns could offer a powerful tool for teachers.  

Investigating chemical p-prims 

A science student looking at a flask filled with a pink liquid

Source: Jupiterimages

In 2005 we undertook an interview study informed by the p-prim theory in secondary schools in the Cambridge area. We interviewed 46 secondary students about a range of simple phenomena - changes of state, mixing, reactions- and asked them to explain what they thought was happening.6 The quality of explanations varied considerably among the students, and even some 15-16-year olds offered vague explanations or gave answers clearly at odds with what they were taught in school. In some ways the results were similar to many previous studies, and reinforced existing findings about the problems learners often have using particle models in conventional ways.  

We also analysed the student responses to see if there was any evidence that their thinking might portray the influences of intuitive pattern-matching. Finding such intuitions is not easy, both because the process is unconscious (and so non-verbal), and because once such a pattern has been identified it becomes a permanent aspect of thinking that no longer needs to rely on the original mechanism. Despite this, we identified several examples 

Messages for teaching chemistry? 

The patterns we found in students' explanations of common chemical phenomena resonate with misconceptions found in many previous studies, and seem to be based on common ways of thinking about the world that can actually be quite useful in many situations. But these ways of understanding chemistry may stand in place of the explanations taught in class. 

If a student has an intuitive understanding of a phenomena then there is no imperative to seek a formal explanation  - and teaching is likely to be misinterpreted to fit their intuitions. This can be especially insidious when we are dealing with what seems 'naturally' so, rather than a logically developed position that is open to analytical exploration. 

However, identifying students' intuitive responses to chemical phenomena can also provide the teacher with ideas for building on those intuitions in more appropriate ways. One 15-year old girl, for example, expressed surprise that when 25 cm3 of water was added to 25 cm3 of ethanol, the resultant mixture occupied less than 50 cm3. She found this counter-intuitive, and in attempting to find an explanation suggested that: 'I would have said that it would absorb some of it, but I don't know how two liquids could absorb each other'. This notion that one material can be absorbed into another offered potential for being exploited in terms of a particle model of liquids that could be compared with the porous structure of an absorbent solid.

Similarly, though we have reservations about any chemical interactions being seen as a result of one active substance, it is clear that such ways of thinking are helpful in developing some understanding of displacement processes. One 14-year old suggested that bubbles seen as salt dissolved in water might be 'hydrogen or oxygen that has been displaced by the sodium chloride - and they've been virtually kicked out because the other is bigger and more reactive'. There are several errors here, but again the student's conceptualisation offers a useful starting point that a teacher can work with.

At the moment our work is provisional. We looked to see if the notion of p-prims that has been extensively used in researching physics learning might be useful in interpreting learners' thinking about chemistry. Our study suggests this approach does indeed have promise. Our candidate p-prims should be seen as conjectures to be tested further: can they be found in other samples?; what proportion of learners think in these ways?; how consistently do they seem to be applied by learners?

However, if further research supports our initial findings, then this could be significant. We may start to understand much better why so many students develop chemical misconceptions, and why they often retain these ideas in the face of extensive teaching of the 'correct' chemistry. 

More importantly, if certain intuitive thinking patterns are found to be common to most learners, then research is needed to find ways to teach our subject by tapping into these powerful learning mechanisms rather than being undermined by them. 

What can teachers do?

In the meantime we would advise teachers to be aware of the possibility that powerful unconscious mechanisms may be leading to students developing intuitive understanding of chemistry that can be inconsistent with target knowledge. Until we learn a lot more about these processes we can only offer general advice to teachers in how to respond.

  • Focus on explanation. Regularly ask students to explain what they think is going on in chemical processes - and why. Look for counter-examples and logical flaws in inappropriate explanations, and work through these with students. Reiterate the accepted explanations and mechanisms of chemistry at every opportunity.

  • Provide diverse contexts. Choose the phenomena presented to students carefully, to 'help' them 'see' things in a different way, compare their explanations to different phenomena and help them spot similarities and differences. In particular, present students with different contexts for the same phenomena, for example, dissolving liquids in liquids and solids in liquids; ask them to notice the similarities and differences (even when phenomena could be thought equivalent from the teacher's point of view, this may not be so from the student's point of view). 

  • Attend to language. Take careful heed of student language, in particular where what seems imprecise phrasing may actually reveal the types of thinking we have identified. Often students have learnt specific chemical words (dissolving, reacting, neutralising), but they have not constructed a firm meaning for them. Ask students to explain these terms without using the word, so that they clarify the meaning of words, and to spot the kind of patterns students are using to understand phenomena.

Finally, remember that most chemists and chemistry teachers have managed to shift their intuitions so that the chemical ways of thinking about cause and effect in chemistry have come to seem the 'natural' explanations. This would suggest that as long as we carefully monitor and respond to our students' thinking about the material world, we should be able to help them also develop chemically appropriate intuitions.

Dr Keith S. Taber is a senior lecturer in science education in the faculty of education at the University of Cambridge, 184 Hills Road, Cambridge CB2 8PQ; Dr Alejandra Garc?a Franco is a researcher at the centre for applied sciences and technological development at the National Autonomous University of Mexico, Mexico City, Mexico.

Identifying students' intuitions in chemistry

1. Component gives property

One common idea among the students was that the properties of materials come from specific components. A 12-year old boy, for example, suggested that water became coloured purple when potassium permanganate crystals were added because the crystals released ink.

It is often quite appropriate to explain properties as caused by components, but as a general principle this leads to the common misconception that atoms and molecules have the same properties of the substance they make up (eg 'copper atoms being brown and malleable'). One 14-year old boy, observing a precipitate when silver nitrate solution was mixed with sodium chloride solution, told us that the solid formed is the silver because 'that is the metal, . silver is definitely a metal'.

So rather than consider interacting systems of substances, some students perceive chemical phenomena as being the result of a single component (another student, a 12-year old girl thought that it was 'dirt' released from salt which made the water cloudy. In this particular case it is possible to show that the cloudiness can be avoided by using previously degassed water and so does not derive from the salt.

2. Changes require active agents

The principle that effects have causes is a useful one in science. However, in chemistry changes sometimes occur without external causes. So if a dye is added to water it will mix, owing to diffusion, which can be explained in terms of particle motion and the internal energy of the materials. But some students seem intuitively to look for an additional external agent to cause the mixing - some students shown this demonstration suggested we must be heating the solution, despite no evident source of heat.  

In another example, a 16-year old boy suggested that oxygen changes to carbon dioxide when it is burned by fire. He explained that 'the oxygen just changes into carbon dioxide, under the influence of the fire and the heat'. He compared this with how (in his understanding) 'the different densities make something a different material. if you put a lot of pressure on something, it will eventually turn into a diamond I think, just because it becomes dense under the pressure'. Physical agents are considered to be responsible for changes in materials, including chemical changes.

3. There is one active partner

For some students we talked to, an interaction involves an active and a passive partner. They understood mixing and chemical reactions in this way, identifying one of the reagents as doing something to the other - causing the other to react. So dissolving may be seen as the action of (active) water on (passive) solute, when, as one 13-year old said 'the water erodes it and washes it'. One 14-year old explained the effect of adding silver nitrate solution to salt solution in terms of it being 'a stronger substance'.

4. What comes naturally  

We also found that some students thought that some substances would react 'naturally', because it was in their nature to do so. Students looked for no further explanation than it was in the nature of that substance or mixture to behave in that way. Similarly, some of our interviewees expected certain systems to change in certain ways, and saw this in somewhat teleological terms. Certain end-states were seen as 'natural', and so sufficient reason for the change to occur. Thus one student said that neutralisation would occur so that an acid could 'balance out' the alkali.