To answer the question that was asked: There are N factorial
possible sequences, and most of them (if not all) can be made
to work satisfactorily.
If you have a theme to the course, or a particular objective
that you want to get to as soon as possible, you should let
that guide the choice of what comes first.
As one possibility -- certainly not the only possibility -- consider
teaching somebody how to fly an airplane. In this case, I start with
energy. People's lives depend on getting this right. "Energy" is
literally the first word in the title of chapter 1 of the book: http://www.av8n.com/how/htm/energy.html
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6. Energy ( even though I believe it does not really exist)
Clearly energy is an abstraction ... but the idea of "waves" is also
an abstraction. This does not make them unreal. It does not make
them fictional.
So the question arises, do you also believe that waves do not really
exist?
2a) Continuing down this road, I would add that it is more important for
students to understand what energy /does/ ... rather than to memorize
a definition of what energy "is".
In the celebrated story about Dennis and the blocks, Feynman talked at
length about what energy /does/ without ever defining what energy "is".
2b) On the other hand, at a more advanced level, if you really want a
definition of energy, that is available also. I wouldn't use this as
a starting point, but it is a good thing to have "in reserve". As part
of the spiral approach to teaching and learning, this is something that
gets mentioned on the Nth turn of the spiral. http://www.av8n.com/physics/thermo/energy.html