Joanne, a veteran of two of my summer institutes, writes in with this question. Before responding, I did a search for "thermal" and "expansion" in the curriculum guide.
Nothing shows up for "expansion." Lots of hits for "thermal".
My understanding is that that everything about "heat" in physics 2 is about energy transfer via heating -- transfer by conduction, convection, radiation (looks like nothing but qualitative for the latter two, maybe some semi-quantitative for the first). And then a bunch about energy transfer in gasses, with kinetic theory, the microscopic source of the ideal gas law, PV diagrams, etc.
Be very, very sure that students can describe and explain what it means, at a microscopic level, for energy to be transferred via heating. They've gotta be able to say more than a vague "the molecules move around more." Manipulation of equations, and rote problem solving techniques with PV diagrams, will not be of any particular use on the AP Physics 2 exam. The understanding has to be deep and thorough.
But no thermal expansion, as far as I can tell.