Keith S. Taber
Mohammed was a participant in the Understanding Science Project. When Mohammed was near the end of his first term of upper secondary science (in Y10) he told me that in his chemistry lessons he had been studying atoms and ionic bonding. When I asked him what an atom was, he suggested it was "the smallest amount of matter you can get" as well as being "it's the building block of all matter". It is not unusual for students to suggest that atom is the smallest thing that one can get, and then go on to report that it has smaller constituent parts when asked about atomic structure! Mohammed justified his suggestion that an atom was "the smallest amount of matter you can get" by excluding individual subatomic particles from being considered matter:
I: So – if I ask you, what's an atom?
M: It's the smallest amount of matter you can get, it's the building block of all matter.
I: So you can't get anything smaller?
M: No. If, if you – if I, let's say, took the electrons away, then it wouldn't be matter any more.
I: What would it be then, then?
M: It would just be a nucleus.
I: So, if we have got an atom, and you take the electrons away, that would seem to be smaller than the atom? But you are saying it is not really matter any more, it does not count as matter.
M: Yeah.
I: So how do we know what's matter? What's matter?
M: Matter is something that is built out of protons, neutrons and electrons.
I: Ah, so it has to have all three?
M: Yeah.
So from Mohammed's perspective it would not necessarily have been inconsistent to suggest that an atom was the smallest particle of matter possible, despite it having structure, if the definition of matter included suitable criteria. However, Mohammed did not suggest that, for example, matter had to have overall neutrality, and his suggestion that matter is something that is built out of protons, neutrons and electrons had to be amended when it was then tested out. He maintained, however, that if you take all of the electrons off an atom, then you would stop having matter.*
