what she observes. The students who work with the ‘View Particles’ option are
engaged with the scientific explanation of the phenomena. Their task is to relate the
visualised particle theory to her everyday experience and knowledge - her work is a
matter of interpretation of the explanation that she is presented with rather than one of
prediction. The different viewing positions offered by the CD-ROM bring forth
different discourses of what is being represented: the former is in terms of, for
example, ‘water boiling’, while the latter is in terms of the arrangement and
behaviour of ‘particles’.
The Interaction of Modes on Screen
In reading the different modal resources and in specific ensembles as they appear on
the screen the students can privilege one mode over another, more specifically they
privilege image and colour over writing and movement.
In the case of the transformation from a liquid to a solid, the students that I observed
‘read’ the visual representation of a liquid to be a solid even though the writing and
the movement of the ‘particles’ indicated it was a Liquid. This incident is interesting
as it shows how the students engage with the modal representations on the screen
differently to make sense of the representation. In particular it shows the modes that
the students privilege or foreground for them as being the most ‘reliable’ modes in
their reading of the screen at this moment. The multimodal sequence that the students
are watching on the ‘screen within the screen’ is clearly labelled in writing in the
‘frame’, however, and through the use of the yellow highlighted key as being ‘liquid
to solid’. The movement of the ‘particles’ indicates that in the opening screen the
‘particles’ are moving more freely and faster than they are in the final screen in which
the ‘particles’ move slower ‘hardly at all’ and are compactly arranged. The direction
of the line plotted on the graph shows the temperature at the top of the graph as being
‘higher’ than the temperature at the bottom of the graph - that is the directionality of
the graph represents a decrease in temperature. The students’ talk demonstrates that
they understand the temperature is being decreased - that the substance is being
243