Much of science teaching involves teaching about models: scientific
models ,or curriculum models of scientific models. theories,
principles, or using teaching models designed to introduce ideas.
Often, as John implies, these models do a good job as a first
approximation, or a starting point for understanding, or as useful
heuristics in limited ranges of application etc.
Sometimes, however, teaching models are just misleading.
e.g. why do some teachers give pupils the impression that chemical
change occurs because atoms want/need to fill their electron
shells/obtain octets. Complete nonsense of course, but at secondary
level we do not provide a good physical explanation. (Why? they learn
about charge and force?)
Other models are useful, e.g. a shells model of the atom, although
limited. I've strongly argued that the problem here is that pupils
get the impression they've been taught things that are wrong that
they then need to unlearn. (Which of course is not actually
possible.) We should be teaching these ideas explicitly as models,
which have uses, but sometimes need to be adapted or supplanted:
rather than giving pupils the impression that what they learnt before
was wrong and a waste of time (or is that just a UK tendency?) That
would be truer to the nature of science and less frustrating. It
might help them make sense of why the quanticles in a solid are close
packed to explain its properties (hardness, fixed shape, rigidity
etc) AND YET in explaining thermal expansion the quanticles in a
solid move further apart!
Teaching models which aim to get across ideas by analogy, but are not
actually even approximations, are more tricky: and again I think we
need to teach students to appreciate the role of metaphor and analogy
in learning, and then be explicit about these models when we use them.
e.g. does anyone here teach about the change of direction during
refraction in terms of ranks of marchers (e.g. a marching band) or
vehicles with spatially separated wheels moving from one surface to
another (gravel to tarmac etc)? Can a ray of light really be
considered analogous to something with a definite broadness as needed
for that analogy to work?