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Seminar Meetings

Cambridge (Faculty of Education) Seminar Series
Michaelmas Term 2003-4 Seminar: Saturday 18th October, 2003
Challenging pupils through scientific explanations
Dr. Keith Taber, Faculty of Education


At the invitation of Dr. Cathy Auffret, KST visited Chesterton Community College, Cambridge, to lead two 50-minute lessons around the theme of 'explanations in science' to a Y9 top set. Explanations would seem to be central to what science is. A naïve view might claim that science discovers knowledge about the World, although it might be more accurate to suggest that science creates knowledge through the development of theories. The theories are used in turn to understand, predict and sometimes control the world, and in these activities, scientific explanations play the key role. We might consider theory to be the resources of science, but explanations to the active processes through which theory is applied to contexts of interest. Meanwhile there is research evidence that pupils do not have a good understanding of such core features of science as theory building and modelling.

I would suggest that an explanation is an answer to a 'why' question: but that in itself makes for neither a good explanation, nor for a scientific one. Explanations have audiences, and to some extent a good explanation is one that satisfied its audience - in other words it meets the explainee's purpose in seeking an explanation.

The Context

Chesterton Community College is a maintained 11-16 comprehensive school in the City of Cambridge. Science is set in Y9, but due to timetable organisation the year is split into two parallel half-years. The work was planned for the period after the Y9 students had completed their KS3 science programme of study, and had taken their National KS tests (SATS). The school did not begin the Y10 programme at this point, but rather sought to provide enrichment work for the students.

There were 28 students present for the session: 9 girls and 19 boys. When asked what they enjoyed about science there was a wide range of responses, but a number of points were made by at least three members of the group. The most popular suggestion was various types of practical work - doing things, such as experiments and investigations - which was mentioned by most of the group (17 students, 11 boys and 6 girls). Six students (four boys, two girls) referred to learning about how things work or why things happen. Five students (all boys) mentioned finding things out for themselves, and three (two boys, one girl) reported that they most enjoyed activities that gave them independence. Three students (2 boys, one girl) referred to activities that might be classed as discussion (such as exploring and comparing). There were also four references to biology or learning about the living world (one boy, three girls) and three more specific references to human biology/learning about the body (two boys, one girl). Chemistry had three mentions (two boys, one girl).

There was also a wide range of suggestions for the things this group least liked about science, but only a few common points. One of the most popular [sic] dislikes was chemistry with five mentions (three boys, two girls), on this basis as unpopular as tests (two boys, three girls). A number of themes had three mentions in the group including recalling facts (one boy, two girls) and producing conclusions and evaluations, presumably of practical investigations (one boy, two girls). Three girls disliked aspects of maths in science, whilst writing was unpopular with some of the boys: three referred to the paperwork (such as writing-up), and three to having to do extended writing.

In interviews, after the sessions, two of the girls suggested they liked the experiments and particularly when they could design their own experiments. They enjoyed 'putting ideas into practice' and found science more interesting when they had more freedom and independence in their work.

Two boys who were interviewed also cited the experiments as enjoyable, because they were hands-on, and they felt they were doing the science themselves. They found science interesting because they liked "finding information out" and seeing how things worked - particularly "those questions which might have bugged you for years". They liked 'working things out themselves'

The tasks

The sessions were designed to build-up to an activity where students would be asked to evaluate a set of 'explanations' as poor or good scientific explanations, and to justify this by reporting their criteria for the judgements. The activities leading-up to this were meant to get them thinking about the nature of explanation in science. The students were given a short questionnaire at the start to find out what they enjoyed about science and to gauge their existing notions about scientific explanations.

When asked at the start of the session 'what do you think makes a 'good' scientific explanation?' there was again a wide range of answers - some quite eloquent,

"A logical, clear explanation of why something is like it is or why it happened. Using what you know to help you explain."

Ten of the responses made reference to the explanation being based on "evidence to support it" (even "conclusive evidence") or proof,

"You need to use facts and evidence for your explanation and see how it all links to prove your scientific explanation"

Nine of the students made references to the effect that the explanation should include reasons or explain why.

"one that is simple, but explains reasons and details"

There were also nine references to the importance of clarity.

"One that clearly explains the problem at hand, explaining each possible outcome."

Eight of the students referred to simplicity - not "too complicated", "as simple language as possible" - or being 'to the point'.

"something that is clear and straight to the point, it is better if you can make it as short as possible, but should still try and use all the main points, or what you have to know."

Seven of the students thought that good scientific explanations should be concise.

"Concise, clear and simple explanations including diagrams and reasons for results."

Six of the students referred to the need for detail, or for the explanations to be in-depth.

"Detailed evidence and reference from text"

Five of the students thought that good scientific explanations should be comprehensive

"An explanation is good when it gives a complete overview as well as detail on every specific aspect."

Four students emphasised the need for the explanation to be capable of being understood.

"One that is easy to understand and use, and one that gives information needed and no more"

Three of the students thought that the explanation should show patterns of trends in the data,

"A good clear answer that explains why things happen like they do, and shows any patterns or trends in their answers."

Three thought it should include reference to when (the conditions - "what you did to make it happen") under which it would apply.

"Something that takes into consideration the conditions from which you obtained your info to make an explanation, clear & concise, not necessarily the obvious result, conclusive."

When asked if they could 'give an example of a good scientific explanation?' twelve of the group did not make a suggestion. Newton/gravity was mentioned four times, and Einstein/relativity twice. The other suggestions were photosynthesis; friction; adaptation to habitat; evaporation; why the earth orbits the Sun; the properties of light; unbalanced forces; rate of reaction being proportional to surface area; acid reacting with marble and the ability to rearrange the defining equation for pressure!

"If you're using equations, e.g., for pressure (pressure = force/area) this can be changed to: [triangle with F at apex over AxP] this can be used when any of the factors aren't known. Making it more useful."

Some of these responses did not give sufficient information to be certain what the actual 'explanation' being considered was: so by itself "plants photosynthesis to make food" cannot really be considered an explanation, and "why we go round the sun" provides an invitation for an explanation rather than the explanation itself.

A Newton supporter thought that "Sir Isaac Newton did a good job on explaining gravity", whereas an Einstein fan proposed E=mc2 as his example of a good scientific explanation on the basis that "it makes sense, it works, it can be understood, it explains how". If this is an informed and measured judgement then this particular student is surely among the 'gifted and talented'!

The 'explanation' of 'what light does and how' could be considered more as a summary of properties,

"light travels in straight lines, it goes at a speed of ... per minute. Light is white but can be split into many colours. Light can be bent or changed in different ways, there are ... Light cannot travel through opaque objects etc." (... in original!)

However some of the suggestions could be considered to be close to genuine scientific explanations,

"Water evaporates because heat causes the water molecules to turn into a gas water vapour, which can be seen as steam"

"More CO2 is produced on a piece of marble with a larger surface area (in hydrochloric acid) than on a piece with a smaller surface area because there is more of it exposed for the acid to dissolve therefore causing more CO2 to be produced."

Suggest an explanation:

This was intended as a warm-up activity to introduce the notion of an explanation being a response to a 'why' question. A series of 'why' questions were prepared, including a number that it was not expected the students would 'know' accepted answers to (thus 'suggest an explanation'). It was suggested that students should work in pairs, and copies of the set of questions were distributed around the room so that students would have a choice of questions to consider (but there was not a full set of questions for each pair). In the event the students became quite engaged in this activity, and it was allowed to run on whilst they remained on task and seemed to be enjoying the challenge.

One of the most noticeable features of the set of responses was the extent to which answers were produced which were coherent, often extended, and matching scientific explanations. Although some of the questions should have been familiar from school science, this was still striking. That said, there were a number of dubious suggestions, and many of the explanations might be considered incomplete.


The students then received a presentation on the theme of scientific explanations. This took the line that scientific explanations needed to take into account logic and theory, i.e. that the explanation needs to be rational, and the explanation needs to draw upon accepted scientific ideas. As the notion of 'theory' is itself known to be difficult for students, they were also told that scientific theories are ideas about the world which are well supported by evidence; are internally consistent; and which usually fit with other accepted theories.

To get across the idea that scientific explanation can be quite complex, two examples were considered: the size of the known universe and natural selection. The different types of evidence that collectively support a Darwinian explanation of the evolution of modern life forms were reviewed (the 'explanation' to the question 'why do we believe life has evolved'?) The cosmic distance ladder was used as the second example - an explanation for how we have come to be able to put a value on the distance to the farthest detectable objects.

These two areas of scientific theory gave a glimpse of how sometimes scientific explanations can sometimes depend upon chains of logical connections (and so on a significant number of potentially incorrect assumptions), and may sometimes be based upon a weight of circumstantial evidence where definitive proof is not logically possible. These scientific 'stories' - one from the life sciences, one from the physical sciences - were thought to be suitable to interest the more able student - as well as giving an excuse to project images of dinosaurs and stars!

Explanations wanted

The students were then set a task to think about over break - 'what are the questions you would most like to know the answers to'? It was thought that this might be a useful short activity to find out what kind of question motivates the curiosity of able 14 year-olds. (N.b. Y9 pupils are 13-14 year olds, but by July the majority will have reached 14.) it also gave an opportunity to see whether the questions posed to the students at the start of the session reflected areas of interest.

After the break the students were each given a sheet headed 'Explanations wanted (The questions I'd most like to know the answers to.)', and asked to suggest their own questions.

The questions that students mooted as wanting explanations could be taken as an indication of the interests of this particular group of able students. However, a caveat should be given, in that this activity came after both the presentation and the exercise suggesting explanations to my questions (see above). Clearly both of these activities will have channel student thinking to some extent, and some of the suggested questions seem to strongly reflect some of those posed to the students.

Nevertheless it is interesting to look at some of the questions posed. Many of the questions related to biology, especially human biology, or behavioural science. Although there was some interest in 'cosmic' questions, there were relatively few questions relating to the physical sciences, especially chemistry, among the group. Many of the questions would either form a useful starting point for science that is in the curriculum, or could provide the basis of interesting enrichment work.

Sequencing explanations

The next activity concerned sequencing explanations. This was intended to build upon the earlier presentation where the complex (i.e. branching, or daisy-chained) nature of explanations was considered. The task was illustrated on the OHP, using the quesition 'why do solid substances melt when they are heated?' A set of statements, including some false ones, were moved around the projector glass to form a possible structure for a valid scientific explanation of the level expected in the school curriculum.

The students were then provided with a choice of two examples to work on in small groups. They were given information about the task:

"At the top of the sheet you will find a question. The statements on the sheet may help you construct an explanation to answer the question. However, you may not need all of the statements, and some may have been included to confuse you!"

And a set of instructions:

"Cut up the sheets so that you can rearrange the statements. Collect the 'blank' sheet with the question printed at the top. Arrange the other statements on the page to give an explanation that you are happy with. You can join the statements in any order. You may wish to add connecting words - 'because', 'so that', 'when', 'and', 'therefore' etc. You may add other statements if you think that they will improve the explanation. When you are happy with your explanation, then stick the statements down. When you are finished, have a look at the explanations produced by other groups."

The groups were given a free choice between a life-science example ('Why do plants die if kept in the dark'), and a physical science example ('Why is it important to use renewable power sources?'). These were expected to be questions that students would already have some ideas about, so the focus of the task was thinking about how to structure the explanation rather than working out what the answer could be. Both examples included some irrelevant or false statements, but these were included less to catch students out than to reduce any expectation that there was a single correct response comprising of a particular arrangement of all the statements. A3 sheets were provided for the responses.

Only one group completed the 'power' option. This group were able to sequence an explanation with three separate 'threads' or aspects - the greenhouse effect, the production of acid rain, and the disparate timescales for the production and use of fossil fuels. Each of the threads is relevant and logically constructed.

Most groups chose to work on the question about plants, and responses of varying levels of complexity were produced. Some groups tended to produce longer, involved explanations. These tended to include some flaws in the logic of the explanations.

It would seem that some students felt it important to include the information that "photosynthesis is a chemical process where carbon dioxide and water are reacted to form sugar (glucose) and oxygen". Presumably this was something that was emphasised in lessons, and they recognised its centrality to any discussion about photosynthesis. However, in terms of the specific question asked here it was quite peripheral. It would certainly be possible to include it in an explanation, but students seemed to rather 'force' it into their responses.

Some of the suggested explanations included connections that included quite complex sequences of statements. It is clear from some of the responses that students do not always use appropriate conjunctions to denote the correct logical relations between statements. This may be a lack of understanding of the logic, or a poor appreciation of the meanings of the words themselves. In some of the responses, some connections were not labelled at all. This may reflect the difficulty of selecting the correct conjunction, or may simply reflect lack of time to complete the labels.

Evaluating explanations

The final task, which in some ways was intended to be the culmination of the sequence of work, asked students to select examples of poor and good scientific explanations. Again working in groups, students were provided with a set of 'explanations' on a range of topics. They were also provided with two A3 sheets on which to glue their chosen examples. One sheet was headed 'poor scientific explanations' and had a series of boxes for students to complete the statement 'This is a poor explanation because ... '. The other sheet, headed, 'good scientific explanations' had a single box to be completed: 'A good scientific explanation ... '

Students were required to select examples of poor scientific explanations or good scientific explanations, and, also, to justify their choices. However, for poor explanations they were asked to explain the faults in each selected example, where with good scientific explanations they were asked to give an overall justification for their selection. This was deliberate, as it was hoped that students would apply a common set of criteria for evaluating explanations (which all the good scientific explanations would need to meet), and so an explanation could be judged poor on one of several criteria.

A number of the options selected as examples of good scientific explanations were in fact flawed. Some of the critiques of 'poor scientific explanations' are at the level of 'it is wrong' or 'it does not make sense'. This may represent the level of understanding that these students brought to the task, or it may be that in at least some cases reflect the ability to clearly explain their reasons. However, there are a number of examples where reasons that are more specific were suggested.

Students' responses to the sessions

At the end of the sequence of work the students were given a second short questionnaire to find out what, if anything, they enjoyed and/or found challenging about the work. Students were asked what (if anything) did you enjoy about the lessons. There were a wide variety of responses to this question, with some citing particular activities, while others suggested features of the sessions. Five students referred to how the sessions allowed them to use their own theories or work out their own answers, and one referred to the freedom to work independently. Three of the students thought the way the session was different to a normal science lesson made it enjoyable, and three students specifically referred to the slides that had been shown (another referred to the sessions being more visual). Two students each cited the cutting and sticking activities, the hands-on nature of the activities, and the opportunity for free discussions.

The responses are interesting, although it is worth bearing in mind both that any lesson with novelty value is likely to be appreciate by some students, but would soon lose that novelty value if it became a regular event; and that designing one-off enrichment lessons clearly provides opportunities for the teacher that may be harder to find within the usual schemes of work.

There was less divergence in responses to the question what, if anything, did you find challenging in the sessions. Two students were unable (or unwilling) to suggest anything they had found challenging. However four members of the group had found the critiquing mooted explanations activity challenging, and five cited the cutting-and-sticking activity. This latter suggestion reminds us that activities that involve cutting-and-sticking (or, say, colouring) may still involve considerable cognitive demands - such as "deciding if something was relevant in the flow charts". This may be worth bearing in mind as some pupils clearly enjoy these - as one student put it - "kinetic activities".

The most popular suggestion for something challenging, however, was the set of questions students were given to answer as a warm-up activity. Nine students suggested this as a challenging activity, and at least one of the students had identified something pretty fundamental about the nature of providing explanations: "if you get an answer you can always ask why again and you can never explain it all".


The work discussed in this seminar has two main threads. The data collected provides some information about how well more able 14 years olds can appreciate the nature of scientific explanations. More importantly, for present purposes, it provides us some information about the type of activities that more able students, of this age, enjoy and find interesting.

This particular group of students certainly demonstrated quite intense involvement in some of the activities in the session. From their own actions and words it seems that they particular appreciate the feeling of having some choice, and activities they consider hands-on, and offering tem some sense of independence. My feeling is that we might almost equate this to more open-ended activities, where they have to work through to an answer, rather than feel that there is a given answer to be spotted in a book.

It is also clear that these students appreciate work of the right level of demand, and are very aware of the level of work that is of benefit to their learning. They do not like frustrating impossible tasks, but - equally - see little point in tasks that require minimum thought. It is reassuring that these able students associate having to think about a task with effective learning. As a personal observation, I felt that generally these students become quite involved in the activities, and - some at least - perhaps even reached that state that has been described as flow where they become engrossed in a task and lose awareness of the time passing.

As a final thought, it is clear that what is suitable as an enrichment activity does not simply translate into routine classroom activity. The science which was used as the context was wide-ranging, and assumed that a great deal of (more routine) teaching of the curriculum had already taken place. It would be an interesting exercise to consider how the episode of teaching/learning described here can best inform more 'routine' teaching.

Acknowledgements: Thanks are due to Dr. Cathy Auffret for inviting me in to work with her students, and for setting-up the sessions, and to the Y9 students for their enthusiasm and engagement.