‘why is it happening?’. At this point the task of the students shifts from ‘observation’
of the screen to predicting and theorising what is happening.
In asking the students to explain what is happening on the screen the teacher’s use of
language distinguishes between the ‘water’ in the pan and the liquid on the lid of the
pan. The teacher’s use of everyday and scientific terms to describe a liquid serves to
mark what it is that the students are being asked to explain and attend to in this
instance - that is, the liquid on the lid of the pan. The scientific word ‘liquid’ is
connected semantically with the word ‘particles’ in a way that the everyday term
‘water’ is not. The semantic distinction between ‘water’ and ‘liquid’ indicates the
specific but everyday character of the water in the saucepan in contrast to the
generalised character and ‘scientific potential’ of the ‘liquid’ on the lid of the pan.
The multimodal sequence displayed on the screen, together with the talk of the
teacher, enables the students to theorise that something is happening that cannot be
seen. At this stage the students draw on their everyday knowledge of boiling water in
the home to understand that the unseen entity is steam and that the process that they
are observing is condensation. In the ‘Hide Particles’ viewing option the gas
‘particles’ are not visible and they therefore need to be talked into existence - a
narrative overlay is needed to explain the representation of the empirical phenomena
that is displayed on the screen.
A student offers such a narrative in her explanation of condensation. In explaining
condensation the student speaks of the water and the steam as unconnected entities,
she does not link one to the other as in a process of transformation. She suggests that
the steam ‘comes up’ through the water - that the steam exists separately in the water,
that it is what makes the water ‘bubble’ and that the steam comes out of the top of the
water. The student’s spoken representation of the relationship between the gas
‘particles’ and the water is an accurate re-presentation of the visual representation of
the transformation from gas to liquid that is shown in the ‘View Particles’ viewing
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