Chemistry Reference
In-Depth Information
6.3 Learner: Experience with Models
Students come to chemistry lessons with their experience of models in three
areas: their own toy models, for example, soft toys, car or ship models. They also
know concrete models of other school subjects like biology or geography, in
mathematics they may even be used to mental models: most graphs can be shown
by mathematical terms or formulae.
Toys
. Children like to compare their dolls with themselves or others. They find
out that many characteristics are the same in model and in the original: for example
place and form of mouth, nose, eyes and ears. They also realize that there are
functions, which the doll does not have: the doll does not eat or breath.
This experience is contrary to the understanding of scientific models. If young
students take a structural model, they cannot compare it to the original: they are not
able to look into the salt crystal, to recount the coordination number 6/6 of ions in
common salt crystals. They find coordination numbers only in structural models.
Due to the learners experience of concrete toy models the scientific model has to be
developed and defined step by step.
Fun with models
. The fun that children have playing with their dolls or car and
ship models can be used for working with models of the structure of matter
in chemistry. It has to be connected to an activity-oriented introduction to the
scientific world of models, for example by building close-packed sphere models
or crystal structure models.
If you show the packing of spheres for the sodium chloride structure to students
(see Fig.
6.3b
) and ask them to build this model with white and red spheres from
cellulose (diameter: 30 mm and 12 mm, respectively), they have a lot of fun and
proudly present this model at home. They might even discuss this model with their
parents and siblings and might explain to them what it is a model for: now they are
the experts, who explain chemical ideas to others! Instructions for model building
exercises can be found at the end of this chapter.
If you show a model of the sodium chloride structure (see Fig.
6.3a
) and ask them
to rebuild this model with tooth picks and soft candy of two colors (for example red
and black “strawberries” from sweety producers) they like to do this - and after the
hard work and explanations of the coordination number 6 they may eat their model.
Older students, prospective teachers or even teachers at meetings for teacher
training also like to work with structural models of all kinds, according to our
experience. They convince themselves of the number and kinds of isomers in alkane
molecules or special alcohol molecules, by building molecular models with the help
of molecular model kits. If you offer even spheres of foam, of styrofoam, or of
plexiglass to teachers, they like to build the different sphere packings (see the
modeling course at the end of this chapter), and even like to build difficult models
of unit cells (see Fig.
6.3c
). At the end of the course they can take their self-built
models to the school collection and use them in their chemistry lectures.
Models from other subjects
. Students have lots of experience with models from
other subjects.
Biology
: The school collection normally holds models of eyes, ears
