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6.4. Energy Dissipation and its Perceived Importance
It will first be shown that dissipation was not a prevalent concept used spontaneously.
Next will be some isolated instances where teachers used the concept spontaneously. This
will include an analysis in terms of energy transfers or transformations. One prominent
case of a teacher consolidating her knowledge of dissipation will then be presented. This
will be followed by discussion on teachers’ awareness of the usefulness of dissipated
energy. Prevalent instances of mixing vernacular and technical language will then be
highlighted, similar to the law of conservation. The final subsection details direct probing
for views on how important the concept of dissipation is perceived to be.
6.4.1. Dissipation not Spontaneously Talked About
When teachers were exposed to situations on the PSTS replication interview, in general
they would stop their spontaneous explanation before mention of the ‘end’ where energy
was dissipated. Similarly, most teachers did not include any mention of energy dissipation
on their spontaneous concept maps.

Several methods were used in this study to draw out information about energy dissipation.
They were justified in terms of not wanting to leave the study with a blank on the topic of
dissipation. The first was a set of leading statements on the PSTS interview schedule. The
second was a leading question of the type ‘what has happened to the energy at the end?’ If
considered appropriate, this would extend to asking participants to probe deeper to try to
see if they understood about the notions that:
1) energy is spread out during and at the end of processes / phenomena
(dissipation);
2) this energy is usually not useful (degradation).

The following PSTS interview statements led participants to think about energy
dissipation/conservation:
Q11. The energy the toboggans had while moving down the hill has
disappeared when they have stopped at the bottom.
Q21. Some of the cars’ energy of movement goes into the surrounding air.
Q41. When the battery is flat, its energy has been lost forever.
Q43. When the battery is flat, its energy has been spread out through the
atmosphere.

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