Purposeful practical

The issue of practical work in chemistry is always sure to spark debate. Question marks often arise regarding the precise purpose of different types of practical activity, and it is sometimes suggested that teachers give little consideration as to why they engage students in practical work. In his article, Lewthwaite reports the findings of an investigation into teachers’ thinking about practical work to either validate or dispel this view.

The study was carried out at the end of a five year CPD programme for chemistry teachers advocating the application of Mahaffy’s ‘tetrahedron’, which adds the ‘human element’ to Johnstone’s familiar ‘triplet’ of macroscopic, sub-microscopic and symbolic levels of representation. The programme emphasised the practical experience as a window on the macroscopic dimension of the chemistry experience, with links being made through teaching to the other elements of the tetrahedron. The author notes that there has been little research into which types of practical work (demonstrations, experiments and investigations) provide the most meaningful macroscopic experiences to support engagement with other elements of the tetrahedron. This study probed the thought processes that led to the selection of different activities in different contexts.

The study involved 61 teachers out of 72 who engaged in around 120 hours of face-to-face CPD over the five years of the programme. It is noteworthy that the CPD was not prescriptive,  as teachers were encouraged to make their own informed teaching choices. Quantitative data indicated that teachers’ use of demonstrations and experiments increased over the five years, while the use of investigations declined. Qualitative data was also collected via email, shedding light on the reasons behind these changes.

Although demonstrations were often selected because of their efficiency in terms of resourcing and time, some teachers reported that a well-chosen demonstration is valuable when emphasising the macroscopic element of a concept, which may sometimes be missed when students are performing experiments. Others felt that demonstrations were less valuable as they were ‘too teacher-directed’. Interestingly, the investigations were not widely used despite being seen by many as the most effective way of delivering an authentic experience of science. This was partly due to logistical difficulties, but also the perception that students focus too much on procedure at the expense of scientific thinking. Experiments were often favoured as a middle ground;  appropriate structuring allowing students to engage in multi-level thinking, while permitting training in manipulative skills, without the problems associated with extended investigations.

Of particular interest were the many references to the ‘tetrahedron’ and the macroscopic domain in teachers’ responses, which illustrate the impact of the CPD programme on their practice.  Hence, the fact that these teachers actually were putting a great deal of thought into their choice of practical activities appears to be a result of their exposure to what was clearly an effective programme of CPD, providing lessons for jurisdictions where such provision is being eroded.