A Practical Class

A Practical Class that didn't work - what's the problem?
Roger Maskill
Dept. of Chemistry, University of East Anglia, Norwich

This paper was first given as the plenary lecture at last year's ChemEd-Ireland on "Practical Work in Chemistry" and should have appeared in issue #57 as part of the Proceedings of that conference.

Background

I recently took over the teaching of an access/foundation year chemistry course at the University of East Anglia, UK. This course, which has run successfully for ten years, is designed to take able, mostly mature, entrants up to a level of knowledge at which they are able to start first year honours courses in chemistry. Like almost all chemistry courses at this level it had practical work in a laboratory associated with it.
           The first practical in the course ( la Salters) had the students experimenting with the elements of group 2 and some compounds. The aim of the practical was:
'..to gain practice at spotting patterns and seeing generalisations in practical results..'.
           The students did a range of test tube experiments and observed the reactivity of the metals with water, the thermal stability of the carbonates, the solubility, pH and the reactivity with acid of the oxides and the solubility of the hydroxides. They then had to write up interpretations of any trends in properties they observed. The students all enjoyed it - there was lots of activity, lots of colours and heating and fizzing.
           However, problems arose after the practical because it was very difficult for many of the students to link the events in the test tubes with the background ideas. Also, many did not know what they were supposed to see, and so did not observe the events they were expected to. It was only by massaging the results afterwards and telling them what the results should have been, that writing it up 'properly' became possible. Even then, the results were inconsistent - the changes from strontium to barium were out of sequence.
           These worrying outcomes caused us to consider the practical very seriously. We revisited the discussion (Kerr 1963) about aims and objectives in practical work in school science which took place some years ago. Interestingly, a recently released book (Wellington 1998) discussed the same questions as before, showing that the debate is still going on and that the reasons for having practical work in the curriculum are as contentious as ever.
           It was necessary for us to ask what this practical was really trying to achieve. Did the learners really get adequate value to justify the effort and the trouble involved in putting the practical on and the time the students spent doing it? We went back to first principles and asked why was the practical in the course at all.

The aims of practical work

When Kerr (1963) published his analysis of the aims of practical work he provided a very useful structure of aims with which the aims of any given practical can be compared. Kerr (1963) listed the possible aims of practical work as follows:

to encourage accurate observation
to promote scientific methods of thoughts
to develop manipulative skills
to train in problem solving
to fit the requirements of practical examinations
to elucidate theory learning
to verify facts and principles
to develop investigational methods
to arouse interest in chemistry
to make chemistry more real

IMAGE HERE NOW
Practical work at Chem-Ed Ireland

Aim 5 is not relevant. Aims 1 and 3 probably do not apply, and never did. The observational skills and the manipulative capabilities of our learners are not going to be enhanced very much by looking at precipitates etc in test tubes or by heating substances in ignition tubes and watching for precipitates in lime-water. What they see and therefore think about depends almost solely on what they know they should see. It depends hardly at all on how well they are able to 'look' or how skilfully they are able to manipulate the apparatus.
Aim 6 is difficult to be clear about. To elucidate means to account for or to explain the theory, which doesn't seem to fit a proper relationship between practicals and theory. Usually practicals can precede theory, in order to throw things up which need to be explained, or they can follow theory in order to exemplify it or to show a manifestation of it. he results in the practical above hardly accounted for or explained the theory: if anything they made it more difficult because the observations to be made were not correctly made or else did not fit in with theory.
Aim 7 seems to be closest to what this practical was all about, verifying facts and principles, though even here there were problems since the 'facts' often were not seen until pointed out. The trend in solubilities of the carbonates and hydroxides almost fits what is predicted, but not quite. The lesson after the practical became a very defensive rescue operation to salvage the chemistry theory from the results.

The lesson after the practical became a very defensive rescue operation to salvage the chemistry theory from the results.

Aim 9 is an interesting one since there is no doubt that most of the students enjoyed doing the practical: this is what they expected chemistry to be and they felt that they were 'doing some real chemistry'. This enjoyment is very important and it undoubtedly enthuses many students. However, irritation was caused by the lack of predictability of the results,even though the experiment has been thoroughly tested as small things such as using too much/too little reagent can greatly effect what is seen or not seen.

"exciting fizz-bang experiments are much enjoyed by teachers and pupils alike. Unfortunately, often the more fizz and bang there is, the less the experiment suits theoretical anticipations."

           Anecdotal evidence suggests that exciting fizz-bang experiments are much enjoyed by teachers and pupils alike. Unfortunately, often the more fizz and bang there is, the less the experiment suits theoretical anticipations. Students often feel cheated that the big ideas that they are having difficulties with (such as the meaning of formulae and equations) do not offer exciting manifestations. This may lead to disenchantment and disappointment with chemistry, turning pupils away from the difficulties which really make the study of the subject worthwhile.
           Coming back to the aims of this particular experiment, it is clear that it was mostly to do with verifying facts and principles rather than with observing trends. The students ought to have been told all about the trends to be expected, even the observations to be made, and then they could have looked for what they expected and perhaps the lesson could then have dealt with variations from expectations or the difficulties encountered in making the observations at all. This would have avoided the groans of disappointment when students did not obtain the results which they felt that the 'teacher' expected, even after, as they saw it, much careful experimentation. Many felt that they had wasted their time.
           It is clear that this practical had a complex of aims, non of which were especially well achieved.
It is necessary to consider very carefully what the purpose of this practical was in the course. It is also necessary to work out in some detail what ought to be taught before the practical, in order that the students approach it in the correct way and have the right expectations of what they are doing. As things happened this year, we didn't have it right.

Learning the concepts and ideas of chemistry

           Are practicals like the one described above any good for teaching the (theoretical) concepts and ideas of chemistry? The theories of discovery learning suggest that learners can do practical work and, with suitable guidance, discover for themselves - with all the associated intellectual excitement - the difficult concepts to be learned. Unfortunately this doesn't often work, for many reasons, not least of which is the high level of abstraction of many of the ideas to be 'discovered'. Novice learners especially are rarely able to get much from discovery practicals.
           The integration of practicals into the progress of theory teaching on the other hand, with the practicals reinforcing and illuminating the theory teaching, can work very well and this probably is the way that most teachers use practicals in school curricula. However, this kind of integration is often difficult to achieve because of the organisation required. Even in a university where technical assistance if normally available, arranging for the practical on group 2 metals to follow the theory teaching about the same topic was problematic. Can we always predict, weeks in advance, that a practical on a given Tuesday morning will drop nicely into the scheme of theory teaching?
           Generally speaking, learners doing practicals concentrate their thinking on the task to hand - which is making the practical work. It is a common experience to find that pupils have no idea about the implications of what they are doing. They are completely preoccupied with getting the right observations or best answer. This is what is on their mind, to the exclusion of the chemistry which the teacher fondly presumes is holding their attention. The students are concentrating on the detailed practical instructions half way down page 3 of the worksheet, and that's all they feel they need to know. Practical experiences often don't help
learners to think about the concepts and ideas of the practical.

... the value of a practical for encouraging learners to 'think chemistry' is inversely proportional to the level of practical complexity involved.

It is usually the case that the value of a practical for encouraging learners to 'think chemistry' is inversely proportional to the level of practical complexity involved. For best 'thinking' the practical should be manipulatively trivial.
Putting all these ideas together and referring to my practical above, it is clear that there are considerable problems. We were expecting the students to 'discover' the observations and the trends in the properties and to rationalise these using difficult ideas about ionic size and the effect of this on the crystal lattice energies and solvation energies - very optimistic. Though the practical came after the theory teaching, it was two weeks after and the students heads were now full of something new - polymerisation and other organic chemistry. They had forgotten all about atomic and ionic properties. The practical itself looked deceptively simple - all they had to do was use solid powders, test tubes and bunsen burners. However, as one student told us, for beginner chemists these were all new and unfamiliar things. In fact, for the students the practical operations were not easy at all: they had to concentrate very hard on the instructions and were distracted from what we presumed were straightforward things to think about.
So all in all, our practical was not very well done and much of the blame has to be on the way in which we did it, rather than on any student lack of effort.

Learning the scientific method and the problem solving processes of chemistry

Aims 2 and 4 of Kerr's possible aims for practical work refer to teaching 'scientific methods of thought' and to 'training in problem solving'. But can practicals, as most teachers understand them, like the one described above, provide problem solving activities and learning situations in which useful learning of this kind is likely to be stimulated?
These aims are about teaching the ideas and the thought processes of chemistry and have been around for quite some time. In the introduction and guide to the Nuffield Materials, produced as a major innovation in the UK back in 1967, there is the following statement:
'..our chief concern will be to encourage pupils to be scientific about a problem. This means they must have mental and manipulative skills in the exploration of a situation which, though familiar to us, are new to them.'

Thirty years later in the DES Policy Statement, Science 5-13 in 1998 the following statement appears:
' Science can and should foster a range of desirable personal qualities, encourage curiosity and healthy scepticism, respect for the environment, the critical evaluation of evidence'

All of these hopes and aspirations in theory, and yet in practice the best evidence that we have is that science practicals are not the place to teach problem solving skills, for the very obvious reason that the science itself - the context in which the process skills are supposed to develop - is much too difficult (Maskill and Wallis, 1982). Process skills - ways of thinking - are best learned in contexts in which the learner is very familiar with the ideas and notions to be dealt with. Only then can the higher level skills operate. Pupils think much more effectively when they are dealing with everyday familiar problems, rather than with the complexities of chemistry and physics (Maskill and Wallis 1982).
Again, when our practical is considered with these ideas in mind, we were expecting the students to be much more 'clever' than they were able to be because of their lack of familiarity with the subject matter of the practical. We were expecting too much of them.

So what are we to do?

           Common sense, as usual, prevails. Practicals allow the pupils to 'do some science', which they almost always enjoy and as they did in this case. Appropriate practicals could take the form of giving them exercises which exemplify what they have just been learning about in theory lessons - eg. watching carbonates of group two metals precipitate, differentially according to the size of the metal ions, or watching metal carbonates decompose (or not) to give carbon dioxide and the metal oxide, but doing this having been well briefed of what to expect and how to go about it, and what it means. With hindsight I should have taught what the theory leads us to expect, and then set the practical for the learners to find out whether this is borne out in this context, with the students looking for variations from predictions rather than confirmations of it.
           Or it could have taken the form of manipulatively very simple experiments which produce clear and obvious results which need explanation, such as rationalising why magnesium carbonate decomposes on heating to give a gas which turns lime water milky, whereas barium carbonate does not. Again, the background of ideas needed to rationalise these events should have been highlighted so that the learners knew enough to engage with the problem.
           Most of the problems practical arose because of a confusion between the stated intended aims of the practicals (eg. teaching scientific method) and uncertainty in the demands of the practical as the learners tried to achieve it (eg. not knowing what a precipitate looks like, never having used a bunsen burner/pipette/burette etc before).
           A very common sense approach tells you that when the learner knows what they are doing, then they are likely to get somewhere in achieving it. It also tells you that when the teacher has a clear idea about why the practical is in the course - how it is contributing the overall task of teaching chemistry - then the chances are that it will be properly prepared, and that it will be productive for the students. Not taking care with this was our mistake with the practical described above. With only slight modification of the practical itself and of the teaching which lead up to and followed it, much of the confusion could have been avoided. As was stated at the beginning, despite all of the problems the students entered into it with a will, tried very hard and, mostly, enjoyed their time in the laboratory. With a bit more care on my part, they might have got something useful from it and enjoyed thinking about the chemistry as well!

References

DES Policy Statement, 1998, Science 5-13, HMSO: London.
Maskill, R and Wallis, K.G., 1982, Scientific Thinking in the Classroom, School Science Review, 551.
Nuffield Chemistry Introduction and Guide, 1967, Longmans: London.
Wellington, J. (Ed), 1998, Practical Work in School Science: Which way now?, Routledge: London.

Roger Maskill took his first degree and Ph.D. degree in Chemistry. He then moved to a 3 year post-doc at Liverpool as 'Leverhume Fellow in University Teaching Methods in Chemistry', where he had one foot in the Chemistry Department and one in the Education Department. This was followed by two years as lecturer in the Institute of Educational Technology at the OU, with reponsibility for designing science and technology courses. Since 1976 he has been a lecturer at UEA, initially in the Chemical Education Sector and more recently as Head of the Centre for Science Education, acting also as Deputy Dean of the School and Chairman of the School Teaching Committee.

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