What students in school learn from a model experiment depends on how similar the model substances look to the originals. This was reported by a team led by Prof Dr Katrin Sommer from the Bochum chair of Chemistry Education in Rubin, the science magazine at the Ruhr-Universität Bochum.
As part of a carousel activity with various experiments, the scientists had 234 pupils from the 7th grade perform a model experiment on the subject of dust explosions. They then ascertained to what extent the pupils were able to link the experiment to the actual occurrence of a flour dust explosion at the Roland Mill in Bremen. One group performed the experiment with the original substance wheat flour, a second group with similar-looking corn flour and the last group with black toner.
Acquiring abstract knowledge
The students recognized the link between the real context and the model experiment better when the model substance looked more similar to the original: 96.5 per cent of the wheat flour group made the link, as did 86 per cent of the corn group, but only 56 per cent of the toner group.
However, the data from the Bochum team suggests that children in the toner group could acquire a more general concept of the mechanisms behind an explosion; the researchers now want to look at this idea more closely. "Which substance one should use for a model experiment -- one similar to the original or one unlike the original -- thus depends on what you want to teach the children," says PhD student Christina Toschka.
New apparatus for dust explosions
At present, the dust explosion is only rarely performed in lessons using the original substance wheat flour as the experiment is often unsuccessful. To give teachers the freedom to choose between the various substances in the future, Dr Hennig Steff and PhD student Thomas Philipp Schröder have developed a new apparatus for the experiment.
This ensures that the dust explosion is successful with various powders and sources of ignition. They have replicated the apparatus in a workshop with around a hundred teachers, so it is already being used in practice in North Rhine-Westphalia, Germany.
Detailed article in Rubin
You can find more information in a detailed article in Rubin, the science magazine at the Ruhr-Universität Bochum (http://news.rub.de/english/2016-10-21-chemistry-education-learning-model-experiments).
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