Teacher: How do you know that by the particles?
Points at the particles on the pan lid
S4: When you lift up the lid there’s always water there
Teacher: Good yes.
S5: Or when you have a shower and you get out and you feel the mirror
Teacher: Good yes. But how do I know from these particles that Tve got a
liquid?
Points at the particles on the pan lid
In the ‘Hide Particles’ viewing option the teacher focuses the students on observing
the screen to identify the problem space and to make hypothesises based on their
everyday knowledge and experience of the world. In the ‘View Particles’ option the
teacher shifts the purpose of observation to a matter of a visual explanation of the
problem space. The teacher positions the visual display on the screen as a matter of
evidence. The student is faced with the question of what its is that she should attend
to - what is to be ‘noticed’. The student comments on the directionality of the
‘particles’ - they go up and ‘fall back’ down (as they collect and return to a liquid).
The teacher, however, wants the students to focus on the arrangement of the
‘particles’. His ‘hesitancy’ and ‘re-formulation’ in describing what can be seen
(e.g.,,0kay. The water’s bubbling. What can you see coming out of the/ out of the
um∕ saucepan here?”) ‘overrides’ the confusion expressed earlier by the students
which served to separate the gas particles from the liquid. By referring to the gas
particles coming out of the saucepan, rather than the water he bypasses the
transformation of liquid to gas.
Through his repeated gestures with the screen the teacher indicates that the students
should attend to the arrangement of the ‘particles’ on the saucepan lid. The teacher’s
repeated verbal and gestured demand that the students ‘look at the particles’ makes
clear that abstract theorising is no longer adequate: he wants the evidence. The
screen provides a multimodal realisation of particle theory. The change from the
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