Abstract
Ammonium chloride (NH4Cl) and its aqueous solution have been used for observations of recrystallization in science classes to learn physical and chemical properties of aqueous solutions. So far teachers have often demonstrated such recrystallization phenomena, while students have rarely carried out the experiments individually. We therefore developed a small-scale experimental kit for learners to practice easily and individually the experiment on recrystallization of NH4Cl. We used this teaching material in a science class, a science workshop and a research activity. We evaluated its usability and educational effects on learners based on responses from learners and teachers in these learning activities. We also discussed the usefulness of the experiment in terms of the variety and multiplicity of teaching materials in chemical education. This teaching material is easy and safe to operate, and it allows learners to clearly observe the recrystallization phenomena and heat of reaction. Using this teaching material for the science workshop, the learners were interested in the recrystallization phenomena. Moreover, upper secondary school students enhanced their scientific thinking and expression through their research activity with the teaching material. This teaching material can be useful for more systematic learning about variety of substances if it applied to various substances and improved for various learning activities.
