Source: Journal of Science Teacher Education, Vol. 24, Issue 4, p. 763-787, (June, 2013).
(Reviewed by the Portal Team)
This article presents a study, which examined the effectiveness of a specially designed intervention on chemical changes.
The study took place in the wider context of an in-service training course where the key feature was an innovative approach based on the concept of a substance and its transformations, physical and chemical.
The participants were one hundred and thirty Greek primary school teachers.
Teachers answered a written test at the end of Part I, where ‘basic’ substance particles had been introduced, before the start of Part II.
For chemical change, the test consisted of four tasks: a burning candle, hydrogen combustion, iron oxidation (rusting) and heating sugar (thermal decomposition of sugar).
In each one of the tasks, there was a general description of the experiment and in three of the tasks this was aided with a diagram.
Teachers were asked to say what happens at a macroscopic level and what the substances at the end of the experiment are.
At a second level, teachers were asked to imagine magnifying a huge number of times each substance involved, before and after the experiment and draw what would be seen in a submicroscopic view.
The study addresses to the following two research questions:
• To what extent did this course and particularly Part II, improve primary teachers’ understanding of chemical changes?
• How did the particular characteristics of each one of four phenomena and the development of a deeper level of particle ideas affect the teachers’ understanding of chemical phenomena?
The results of this study show that pre-intervention, teachers were found to have a relatively limited ability in explaining chemical changes, which depends on the characteristics of the particular change.
The teachers also held a number of misconceptions similar to those of pupils.
It seems that a vicious cycle appears to be operating allowing misconceptions to persist from generation to generation.
In this intervention, the authors tried to break that cycle by using a new conceptual approach.
First, the understanding of the concept of a substance in terms of particle ideas is established and then, the conditions under which substances can be transformed through chemical changes into others.
Post-intervention, teachers’ descriptions and explanations were found to be significantly improved.
Moreover, the intervention seems to address important ideas, which teachers could apply to new chemical phenomena further to those they had studied during the course.
It seems therefore, that the intervention shows promise towards breaking the cycle.
However, although there was progress, it wasn’t equally spread across all phenomena.
Post-intervention, teachers seemed better able to manage the combustion of hydrogen and the heating of sugar, than the burning candle which had been studied in the course.
This supports the distinctiveness of each instance of chemical change, which contributes to the challenge of teaching chemical phenomena in a systematic way.
This distinctiveness means some chemical changes are probably more appropriate for the introduction of the idea of the chemical change, than others.
A burning candle, which features so prominently in school science, seemed to present more challenges to the primary teachers.
The simplicity of hydrogen combustion or the (plausibly) convenient appearance of the substances involved in the simple version of the sugar heating, seem to have better possibilities for a successful teaching outcome.
However, the effectiveness of such a teaching approach depends also on the overcoming pupils’ known problems concerning ‘invisible’ substances in gas state, such as hydrogen and oxygen.
Further to the selection of the most appropriate case for the introduction of chemical changes in primary school, the development of particle ideas appears to be helpful, if not requisite.
The analysis explicitly indicates that the teachers who showed a better understanding of the particulate nature of matter are more likely to understand and therefore explain chemical changes at the macroscopic level.
The authors would recommend continuous and long term inservice training programs, where duration, timing and frequency of programs are very important.
Together with also enhancing other components of pedagogical content knowledge, the development of such courses for the improvement of primary teachers’ content knowledge could help towards more understandable primary science for both pupils and teachers.