In the case of the transformation from a Solid to a Liquid, for example, the visual
resources of the screen provide the students with a representation of the arrangement
of the ‘particles’ in a solid and a liquid. As the students’ comments below show, the
students’ interpretation of the relationship between the ‘particles’ and the background
representation of the water leads them, however, to see the ‘particles’ as being ‘a part
of’ a liquid rather than to understanding the ‘particles’ as an alternative representation
of a liquid. (The transcripts in this chapter include punctuation to draw attention to
the hesitation, re-phrasing and reformulation of the students and the teacher, as these
contribute to their work of constructing the entities in the lesson. A comma is used to
indicate a short pause, and a full stop is used to indicate a longer pause, and an
exclamation mark is used to indicate a high volume and pitch of voice.)
Lucy: You’ve raised the temperature so the particles form into a
liquid. The particles now have more space to move freely
Kylie: So they can move more?
Lucy: Yeah they can move more freely, ‘cos in a solid they’re tightly
compacted, so in a liquid they’ve got so much more space to
move, ‘cos its all like jelly.
The student, Lucy, sees the ‘particles’, as ‘held in the water’ like jelly rather than
representing the water itself. This student’s reading does not distinguish between the
visual resources of background or foreground (overlay) and as a result her
construction of the entity ‘particle’ is of something that ‘exists within’ a liquid, a
solid or a gas rather than the thing that constitutes it.
The visual representation of the transformation from ‘a gas to a liquid’ in the ‘View
Particles’ option raises the question of what is to be attended to for several of the
students that I observed working with the CD-ROM. The representation shows gas
‘Particles’ ‘coming off’ of a saucepan of boiling water (in which the ‘particles’ are
not shown); these ‘particles’ collect on the underside of the saucepan lid and form
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