Let's all build molecules

You probably noticed the little construction of styrofoam and toothpicks that came home with your child.
The K class all built little water molecules (you only need three styrofoam balls) in what has become a perennial favorite science class exercise. Of course somebody eventually notices that the water molecule looks like Mickey Mouse, and hilarity ensues.
I figured the Silver Surfers needed a bigger challenge so we made methane molecules (CH4). Ideally these are built with perfect symmetry, so the molecular shape marks the vertices of a tetrahedron.

The K class rewarded me with a great heap of Questions in the Question Box. Rhinoceros, squirrels, fish, and the End Of The Earth were among the topics. Silver Surfers had kind of a slow start as far as the supply of questions.

Don't tell them I said so, but the worm that spent the week in K looked to me, uh, shall I say, health-challenged. It also did not appear to have eaten any of its newspaper (for all I know they need the paper to soften for a month or something before they can really devour it). The interesting thing was that the students dutifully recorded day after day (on the observation log) that some of the paper had been eaten. This case of observation-by-wishful-thinking reminds me of Langmuir's discussion of pathological science. That's not a topic for lower elementary, where we do better to apply positive reinforcement to the right sort of enquiry rather than deep critique of error; so I simply smiled and thanked them for their diligence, and brought the long-travelling worm – who perhaps should be named Laika -- home for a decent burial.

I had tried to build a sort of trough or channel to help visualize electricity (balls rolling in a circular path) for my deep-fundamental-question-asker in SilverSurfers. This apparatus showed, to be charitable, sub-optimal functioning. In a way that's a lesson too - - or it will be, if I can figure out how to build a better one (for under ten dollars and in less than four hours). "We tried this in the laboratory several ways and at last were rewarded with success". Also nice would be a way to show energy being captured out of the stream of (balls) (electrons). I tried to build a sort of water-wheel and it was so miserable I didn't even bring it in. (The trough was made of paper-towel tubes. I know, not so great – but the price is unbeatable).
Hmm… with a milling machine I could make an excellent trough in under an hour and under ten dollars. But I'd need the thousand-dollar tool first. Or a router. Yeah. "Honey, I really have been needing a router for a long time anyway".