Chemistry Reference
In-Depth Information
show the big volume of gaseous butane compared with the volume of the liquid: the
drop of butane fills the whole pump with gaseous butane.
Structure of matter
. It is possible to take up the natural philosophers' discussion
from 2,000 years ago: do you get to an end when you divide a sample of a substance
again and again? At the end of all divisions, are there smallest particles of the
substance? Since students do not have experience with particles of matter, the
continuity hypothesis is more obvious to them. After teaching the particle model
students were asked, if they could imagine water particles. They spontaneously
said: “no, because you can spread a drop of water as wide as you want.”
Even when young pupils accept the term “particle” in a discussion, difficulties in
their imagination still arise: they do not use the particle concept consequently.
Pfundt [
12
] demonstrated the dissolution of a blue copper sulfate crystal in water
and asked students about their mental models. The answers were not only variable
regarding a continuity or discontinuity concept, but also the possibility that
particles may appear during the dissolution process (see Fig.
1.7
) or that existing
particles disappear: they “melt together,” and the new substance forms crystals
without any particles - students prefer the continuity theory if they are not sure.
Fig. 1.7
Part of a questionnaire concerning the particle concept of the solution process [
12
]
