Particles’ representation of the transformation of gas to liquid. The water in the pan
is realised as an ‘everyday’ representation of water bubbling in a pan. In contrast the
water that has condensed on the lid of the pan is represented as ‘particles’ moving
against a pale-blue background - that is, only the water labelled ‘liquid’ is realised
visually as ‘particles’. In this way the visual display on the screen draws attention to
(visually foregrounds) the specific transformation that is to be attended to, that is the
change from a gas to a liquid rather than the change from a liquid to a gas.
The focus in this sequence of the CD-ROM on only one of the two transformations
actually being shown demands that the students imagine the movement and the
arrangement of the ‘particles’ in the water and the transformation from a liquid to a
gas.
Making Visual Links and Patterns
The teacher starts the episode by drawing attention to what is not visually present on
the screen - the ‘particles’ in the boiling water. Using the resources of the CD-ROM
he works to ‘compensate for’ the limitations of the CD-ROM in showing the process
of transformation from a liquid to a gas and from a gas to a liquid. He does this by
moving between the representation of ‘a liquid to a gas’ and ‘a gas to a liquid’ and in
doing so he visually links (making a visual comparison) between the two screens.
Teacher selects the Gas to Liquid screen with the ‘View Particles’ viewing option
Teacher: Now Margaret’s got a tough job here because I can’t really see my
‘particles’ down here
Points at the water in the saucepan
But if I know that I’ve got a liquid boiling.
Teacher selects the Liquid to Gas screen with the ‘View Particles’ viewing option
I know if I go back to my original one.
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