Fountains of Chain: Science Take: The New York Times

I've never tried to demonstrate the bead chain demonstration (available from Educational Innovation for about $20, though I'll admit that I'm looking for longer, cheaper beaded chains) from more than a couple of feet off the ground. That height gives a jump out of the beaker of about five inches or so. Supposedly, though, a longer drop (from a balcony, a second or third story, even) will provide an even higher jump out of the container.

Why, however, does it provide that jump above the lip of the container? That's a little more complicated.

The video above says it explains that jump, but I got a heck of a lot more out of the video below.

Where to buy a kiln

At the ASM teachers camps, we use kilns from Seattle Pottery Supply.

We like the front loading kilns and lean toward the 120 volt versions with the digital controllers because they're programmable - allowing for particularly ramp rates, hold lengths, and delay starts. If you ever get stumped, the digital controller looks like this, and its manual can be found online here.

The 120 volt kilns do require breakers with at least 20 amp capacities. You'll know if your circuit has that if it looks like this.

There are other kiln sellers, of course, but make sure to check that your electrical circuits have the right capacity for what you're ordering, that you're getting a front loader (that's the side-swinging door, not the up-and-down guillotine option), and that you're getting a programmable, digital controller. All of that should add up to a good raku experience.

Oh, and while you're at it, throw a piece of Fiberfrax paper on the bottom to protect your kiln from any dripping glaze.

Compound Bars

The bimetallic strip is a tried and true demonstration of thermal expansion. It's available from all sorts of sellers (Flinn, Arbor Sci, bunches of other places). Invariably, though, the bimetallic strip (also known as a compound bar) is exactly the same from every seller. Yeah, the handle changes, but the metal strip is exactly the same - brassy on one side, silvery on the other, curving toward the brassy side.

This summer, though, I went searching to see if there were other bimetallic strips available, other combinations of metals to demonstrate.

It turns out that there are...sort of...

The four bars above are available from Arbor Scientific, but they come with a bit of a warning.

Of the three customer reviews on the Arbor Scientific page, one is pretty solidly and simply negative, "These pieces are just poorly made, and do not work at all. They are riveted together and tend to buckle instead of bend."

Yup, you can see clearly that those four compound bars are riveted together not smoothly joined as the more common bimetallic strip is. Clearly there's some reason why the cheap and omnipresent bimetallic strip is so omnipresent. It works. The two metals are - assumedly - easily and permanently joined.

Has anybody bought or used the four-bar set? If so, what are your experiences?

If anybody wants to see a couple of nice videos explaining the compound bar, check these...

Shape It! Sand 5lb

We don't all have access to a local beach on which to do our metal casting. If you do have access to a beach, go for it, have a blast, just don't send us photos. Nobody else wants to see your beach photos while we're sitting at home in a landlocked state. Just quit it, Amanda.

If, however, you're nowhere near a beach, you're going to need to get yourself some nearer sand for metal casting. In particular, I like the Shape It! Sand (available under a few different brand names). Shape It! stays nice and moist thanks to some polymer additives that stay permanently moist, letting the sand pack together well into whatever little butter tub (or similar container - maybe something metal just in case the molten tin - because that's what I use in class) you're going to be pouring your metal.

And the best price around for Shape It! Sand is at Fat Brain Toys, $24.99 (link and price updated 7/5/18) for five pounds of the stuff in just about any color you could imagine (as long as you don't imagine orange.)

Where to buy ice cube trays & periodic tables

In our summer, teachers camp, we compare the workability of various metals based on their crystal structure, particularly the number of slip planes and amount of empty space ('gappiness') within the crystal.

I won't go all spoiler on you, but I do want to point out where we can get three of the tools that we use in the teaching of that topic.

First, there's the Sargent Welch student periodic table. The reason we particularly like this periodic table is that each square on the table shows the crystal structure (body centered cubic, BCC; face centered cubic, FCC; hexagonal close packed, HCP; etc) that each element takes in its solid form. I like to ask the students (or teachers if it's summer) which metals they already know are workable (usually gold, silver, aluminum, copper). We then check those metals' crystal structures to find them all FCC. From there, it's to the opposite end of the spectrum, to the least workable metals (titanium, cobalt, sometimes magnesium) which turn out to be HCP. (Check out the table in a large, printable form.)

Those periodic tables are available from Sargent Welch in all sorts of formats (8.5" x 11", 11" x 17" - even in French if that's what you need) or as a 50" x 38" poster.

While teaching that same topic, we also use a couple of types of ice cube trays for water bottle ice cubes. The first type of tray has very little empty space between the individual water reservoirs. This relates to the crystals with very little 'gappiness'. These trays can be found from time to time in the summer (sometimes on endcaps at WalMart in the summer, garden section). They can also be found reliably on Amazon, though, and the best deal I've found is a rainbow set of four, two-part trays for $9.99 (as of June 2015, anyway).

The other type of trays have more empty space between the water reservoirs, so they allow us to demonstrate the fact that crystals with more empty space within the slip planes. These tend to be more rigid, more fragile, and less easily found in stores. I don't know if that's because they require more plastic to produce or what, but I do know I haven't been able to find them anywhere in person for a few years. Amazon, however, has a bunch of options to buy them, the best of which gets you four, white plastic trays for $7.99 (again, as of June, 2015). (These are getting harder to find, but here's a link as of July, 2026.)

Where to buy a variac?

The iron wire demonstration is brilliant for showing an application of a solid state phase change, an allatropic phase change, and an real-world application of the idea that different crystal structures do, indeed, affect the properties of a material.

The biggest to that hurdle, however, is finding a way to adjust the AC current traveling through the iron wire, itself. It is possible to do so using very unsafe methods (I've seen it done with a split cord, two copper wires, and a trough of water to which an increasing amount of salt was added, but I do NOT recommend that method), but the best method is a 20-amp variac.

A couple of master teachers swear by the variacs that come from Parts Express, but they're $200, or alltronics, still $170. Recently, however, I found what looks to be the exact, identical variac available for $109 from Circuit Specialists.

Has anybody ever ordered from Circuit Specialists? If so, what was your experience - especially as to the quality of their product?

Crystal growing kits (like teacher camp activities)

I really like that nearly perfect cube of NaCl (Does anybody know why would you need KCl in the solution?) I may make that a task from one of my student aides this year.

Or I may try a few different crystals that come in a crystal growing kit (item 15114) from Flinn Scientific.

Every year in our material science course, the students grow copper (II) sulfate crystals, so I'm familiar with the pretty blue crystals (shown above in the video, too), but I haven't tried the other chemicals (alum, chrome alum, nickel sulfate, and sodium chlorate) that come in the kit and which, I assume, grow via the same procedure. I should know what they look like and will post photos after this year.

Yes, I'm quasi-endorsing the purchase of a Flinn lab kit (though not this one). They're a nice way to get and try a lab once, but I will fully endorse buying the resupply chemicals separately because the kits are always more expensive than the raw materials.

Sculpting with polyurethane foam

We're big fans of Flinn Scientific.

By we I mean the teachers of the summer teacher camps because Flinn cuts us a slight discount with our ordering for the camps, but I've been a Flinn fan for far longer than my involvement in the ASM program. Flinn is a company that provides outstanding service to teachers, offering free workshops on safety and teaching around the country as well as at NSTA and ACS conferences.

Ok, enough gushing, to the material science stuff.

The two-part foams that we use in our summer workshops actually comes from IASCO (the flexible foam is FF-5Q and the rigid foam is RF-4CFCQ in their catalog), but Flinn does sell the rigid foam as C0335.

The video above is neat because it shows the more artsy applications, turning the foam into cute creatures with the addition of googly eyes and pipe cleaners. I also like the giant tower of foam that's behind the presenter. Anybody wanna make me one of those?

Iron wire demo and where to buy the supplies

Update (12/1/24): You can order the wire online from Ace Hardware now - either in 50 ft lengths or in 1540 ft lengths.

For some ridiculous reason, one of the hardest supplies for material science teachers to procure is the iron wire for our iron wire demonstration. It should be the simplest thing in the world to get because it's one of the least complicated things to make, but - for some of us - it's amazingly hard to find just the right wire. Though the TruValue near Chillicothe, MO seems to stock it in bulk, my local TruValue doesn't understand what I want with it and doesn't have it on hand.

Here's (above) a picture of the iron wire (anchor wire, stovepipe wire, black wire) that is exactly what we use in the summer camps, and here's a video of the demo as we perform it, too. That's Master Teacher Caryn Jackson there on the right. She has a nice variac (and some 15-amp fuses) to use. Some of us envy her for her awesome variac.



...and the same as narrated by Beth Eddy...

Thermite Reaction - Smash! Bang! Boom!

There's so much science hanging here in this remarkably simple-to-perform demonstration.

Steve Spangler - former elementary science teacher - her explains that the kinetic energy from the ball bearing's banging together turn into thermal energy - enough to burn holes in the piece of construction paper. He then goes on to show the far cooler - to me, anyway - reaction of iron oxide (the rust on the outside of the ball bearings) and aluminum. Most folks - if they know that reaction - know it as thermite (check a few thermite reactions here).

Typically, though, the thermite reaction involves mixing aluminum and iron (III) oxide powders in a flower pot or some ceramic vessel. The reaction is then started with a separate reaction (it has high activation energy) and then produces molten iron and a huge pile of sparks. It's outstanding to watch FROM A DISTANCE. That whole FROM A DISTANCE and the need for some second reaction means that thermite is typically reserved for high school and college chemistry classes.

Spangler - who didn't come up with the idea, by the way - brings the reaction into far more manageable form by taking a rusty ball bearing (covered in iron oxide) right up against one covered in aluminum foil. Same reactants...good energy to start the reaction (from the KE of the ball bearings)...great sparks.

Yeah, it takes a little practice to get the technique down right, but it's way safer than the big thermite reaction that throws molten iron all over the place. Plus, you get to clean up the rusty ball bearing in the process.

Al _(s) + Fe₃O_{4 (s)} --> Al₂O_{3 (s)} + Fe _{(s or l)}

We can look at this for...

• activity series - aluminum more active than iron, so oxygen goes to aluminum
• energy transfer - kinetic energy becomes thermal energy becomes chemical energy becomes light and heat energy again
• corrosion - We're un-corroding the iron in favor of the aluminum.
• electrochemistry - electrons are leaving the aluminum (so it's the anode) and going to the iron (so it's the cathode)

I am so happy that I just got myself a pair of these rusty ball bearings myself.

First day of awesome AP chemistry, here we come.



Update: If you're looking to buy yourself a set of these, Flinn Scientific offers a slightly larger version of these rusty steel balls (AP 6256) for (as of April, 2013, anyway) $26.60. Plus you get a couple of sheets of aluminum foil, which are easily worth like a thousand dollars or something. They also have a video on their site (that I can't figure out how to embed here)