Matter is atomic ("Skeletal chemistry" 1 of 9)
"This provides the currency of all chemical discourse. Richard Feynman once remarked that if he were to have to leave a message carved in stone that would put survivors of a nuclear holocaust on the fast track to our current scientific understanding, then he would scratch 'matter is atomic'. Without this fundamental understanding of the composition of matter, chemistry would be intellectually amorphous, so it must lie at the bedrock of our subject."
The Three Basic States (Phases) of Matter
This is a nice kinetic model that was developed for blind students, but can be useful for all students. Try using a plastic bag with a constant number of marbles, instead of plastic plates and a changing number of marbles.
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Sweetly Balanced Equations
Using candy to represent atoms of different elements is a fun way to get at the idea that the heart of chemistry is the rearrangement of atoms.
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Balanced Budget Chemistry
And from candy-as-atoms to coins-as-atoms, the values of the coins can be related to the masses of atoms.
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"Skeletal chemistry" article
This is one of the nine central ideas that Peter Atkins lays out in his 2005 article, "Skeletal chemistry." Each of the other ideas has its own list in SMILE.