6.8. The ‘Fuel-Oxygen System’
This additional section will present some cases where I specifically led conversations
about fuels to consider the fuel-oxygen system as discussed by e.g. McClelland (1989),
Ross (1993). This expands the discussion made in the theme on the ‘Nature of Energy’.
For T3, energy was consciously and firmly located in the fuel. This was acknowledged as
a simplified, idealised model. T6 had the same view, emphasising that it was a good,
operational model for young children. However, when T3 was probed on where the energy
came from in combustion, he readily acknowledged that ‘half of it could be in the
oxygen’.
T10 did spontaneously mention that a fuel was not 100% the source of the energy of
combustion, because it combined with oxygen. However, he struggled to think about the
energy associated with oxygen:
I mean oxygen molecules, are bonded together, they’re two atoms bonded
together so they do have some energy in them but; just trying to think now;
(long pause) hmm; … I mean the oxygen itself you can’t actually burn the
oxygen itself.
Further conversation revealed that he reinforced the role of oxygen strongly with KS3
pupils – usually saying something to the effect that although we have to buy food and fuel,
we equally need the oxygen. The final conclusion was to emphasise that energy is released
when the two are brought together:
RI: … because the way I like to think about it / what if you take your fuel
to the moon, does it have any energy then?
T10: So you can’t burn it you’d have to take your oxygen yes exactly.
RI: But then it’s a matter of what is appropriate for the kids?
T10: Yes I think they could / if it was consistently explained in that manner
if you were saying, er, it’s bringing the two things together that gives you
the energy on its own it doesn’t have it. Em I think they’d be perfectly
happy / they’d take on far more stuff than that so I think that’s not a
problem. But I think it isn’t explained, and there’s a sort of everyday, you
know from the calories point / your kilojoules on your packet of biscuits to,
you know –
RI: – yeah which is locating the energy solely within the food or the fuel.
T10: I have explained that just because we don’t pay for the oxygen that we
don’t appreciate it, it’s er, it’s just as much part of it.
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