How do you make science real? Chemistry Edition

Homeschool means that I need to know what I am talking about, at least most of the time. I feel like I have a handle on history, biology, writing, PE, civics, and grammar. Middle school chemistry, not so much. I took chemistry in grad school so I get the concepts (mostly), but I have no clue how to teach this stuff to a 12 year old, not even a really smart one. Thank goodness for the interwebs and amazing teachers that create really cool curriculum. We have been having fun with understanding how molecules react to heat. This is a simple home experiment we did so we could see that air does expand (and the molecules speed up) when heated and contracts (the molecules slow down) when cooled.