Chuck's comment, "I fear that they are mainly arguing as to what a correct Multiple Choice Test would include," seems to be the operative one for me. There have been too many occasions where I blame our elementary, middle and even high school educational systems for wanting only to label things so they can be memorized rather than emphasizing the models of how the universe works.
So, to add to the list that others have already created, I'll mention the distinctions between mixtures and compounds that our children had to learn (and one of our sons now has to teach to middle school students) and the definition of mixtures as things that can be separated. So where do glasses fit into this scheme? And are neutrons mixtures of electrons and protons since under the right conditions one can separate electrons and protons from a neutron sample?
Richard Bowman
Dept. of Physics
Bridgewater College, VA, USA