Making ULTRA-BRIGHT GLOWING GOO

Barnaby Dixon is an impressive puppeteer that I first heard about probably ten years ago. If you haven't checked out some of his work, do yourself a favor and spend a few minutes there first.

In this instructional video, Barnaby explains how he uses a thermoplastic polymer - a polymer that becomes flexible when it's heated above some temperature but is rigid below that same temperature. It's a great example of the polymer's glass transition phase change. Because polymers are mixtures, they don't necessarily have definite melting temperatures as pure substances like elements or compounds do. Instead they have ranges of temperatures during which they aren't quite solid or liquid but are flexible and moldable - think of hot glass being shapeable but not liquid.

I have some of this at school. It used to be available from Educational Innovations. That's where I bought it, but they sadly don't carry it anymore. Of course, just about anything is available at Amazon if you search for pcl moldeable plastic.

How to Make a Matchbox Rocket Launching Kit

I made paperclip-rubber band bows and arrows when I was in high school. They would launch paperclips maybe ten feet and with absolutely no consistent aim at all.

This is a few quantum leaps better than my amateur armory.

Be safe out there and launch these outside and not at people...but do make them.

World's Roundest Object!

Be careful when discussing this video with your students. This is about the world's roundest sphere...sphere. It's not a ball. It's a sphere.

Just saying.

'Cause I know I've said ball in front of my high school students, and it took me a while to get the boys' attention back.

(In a related aside, my wife is listening in as this video plays. She lost control at 6:22 when the narrator said "Newtons, Joules". To quote her: "heh, heh...Newton's jewels...heh, heh".)

This 'world's roundest object' is more about the basis of our metric (now the systemé international d'unités or SI) than it is about materials science. There are, however, some serious challenges involved in making a material that won't decompose, that won't get dirty, that won't wear away, that won't change over time.

Here they have created - according to the scientist at 7:25 - a single crystal of silicon with 'no voids or dislocations' and containing only one isotope of silicon, making the material just slightly less valuable than absolutely, perfectly, priceless.

Complete History of the Avogadro Number

Around 0:50 into the video, our meandering narrator mentions that he wasn't able to find a single source with correct, complete information on the history of the Avogadro Number...which makes me wish he'd provided sources for his information. Otherwise, how do we know that what he's telling us is correct?

(As an aside, I've always called it Avogadro's Number. Maybe the the and lack of possessive is a British thing. I'll admit that I don't remember how my professors at the University of Aberdeen referred to it.)

I will say that this is an amazingly thorough and likely correct history of the development of the concept and number of the moles. It goes through from Democritus through the Karlsruhe Congress and all the way to the modern measurement of Avogadro's number via a nearly perfect sphere of silicon.

I need to watch this video a few more times until I'm more familiar with all the steps in this development so I can tell the story to my students.