into clusters (drops of water) and fall back into the pan of boiling water. The
‘particles’ are not shown in the boiling water; that is shown as having ‘bubbles’ in it.
Several students made comments like the following one that a student, Kylie, wrote
on her worksheet:
I have decreased the temperature and the particles go up singularly but
come down in clusters.
This observation focuses on the number of ‘particles’ and directionality; while the
observation is accurate, the student’s comment highlights a difference to the point at
hand, that is, that the single ‘particle’ represents ‘a gas’ and that the ‘clusters’
represent a liquid. That is the word ‘particle’ is used to signify ‘molecule’ in a gas
and ‘droplet’ in water. The representation serves to foreground the transformation
that is to be attended to - the transformation from a gas to a liquid. The
transformation of a liquid to a gas is represented by the use of a bubble texture which
‘stands for’ ‘a kind of particle’. This representation of ‘Particle’ is problematic as in
the attempt to foreground the transformation of a gas to a liquid the representation
visually separates the gas ‘particles’ from the boiling water. As a result some students
‘read’ the particle rising from the water as ‘steam coming up through the water’
reading the particle and the bubble texture of the water as visually separate entities.
This separation serves to construct gas and liquid ‘particles’ as different kinds of
‘particles’, rather than as different arrangements of ‘particles’: as such the move from
a specific representation of a ‘liquid’ to a generalised one of ‘states of matter’ and
‘transformation’ is difficult for these students to realise.
Within the CD-ROM it is the visual representation of the transformation from a liquid
to a solid that appeared to be most problematic for some of the students to ‘read’ and
to make sense of. The difficulty these students found in ‘reading’ this image is, I want
to suggest, a consequence of the designers’ of the CD-ROM’s use of the modal
resources of colour, texture and shape, clashing with the students’ principles for
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