Undercooled: A Materials Education Podcast

[MUSIC]

Hello. Welcome back to another episode of

Undercooled and

Materials Education podcast.

Today, Tim and I are going

to talk about demonstrations,

mostly because this was Tim's life for

quite some time before

he became a lecturer.

Sure was.

Let's start with having Tim tell you what

he used to do. Go ahead, Tim.

Sure. Once upon a time when I started at

MSE, my first job in MSE

was being the support guy.

So part of that was helping out with lab

classes. But another big part of it was

developing and implementing the classroom

demos for mostly for our intro classes,

a couple advanced classes as well. So it

was a great learning experience for me.

Hey, what is all this stuff? It was a

good way to get into the field. But

working with different

faculty to come up with ideas for demos

that they wanted to do in

their classes, then trying to help

make those real was a really interesting

bit of work that I did and

something I would definitely

recommend to anyone who wants to figure

out a little bit more

on the teaching side.

Great. So why demos? What do you think

the value of the demonstration is?

You know, I could see three main

arguments in favor of having classroom

demos. One of them is

engagement. They're fun. That's in its

own right. There is some

value to that. That's not going to

be enough by itself. But sometimes you

just want to say, hey,

let's do something different and

interesting to bring the students back to

life a little bit. So

that's fine. And for that, almost

anything works. The second aspect and the

one that I'd argue is the

most important out of these three

is the fact that you can have students

make and test predictions in

real time live while they're

learning the content and to have a much

faster, much faster

feedback response than what you get

in a real lab when you're doing

experiments or when you're doing

simulations. You know, that can be a

year's effort to find out whether your

prediction was correct.

So to find out in minutes,

do I understand this? Am I thinking about

it correctly? That's very powerful.

And then the third aspect is that demos

can be used as a launching point for a

further investigation

on the student side. So that can be a way

to develop into an out of

class assignment, like a

homework, for example. And that can be a

nice way to say, okay, we're learning

this stuff in class,

but now go out and connect it to the rest

of the world. That's

pretty good. So of course,

I've been teaching intro to materials for

a very long time, and I

don't think I could do it without

doing demonstrations. Otherwise, it's

just us talking, you know,

yap, yap, yap in front of the

class, and they don't really believe that

anything I'm saying is

true. So at least the demos show

that there's some real life thing going

on. And I tend to far

prefer physical demonstrations

to all the virtual demonstrations that

have been coming up. I've

seen a lot of them. And I,

you know, in my opinion, I just don't get

it. They seem like very black box

modules, where you have

little sliders to change parameters, and

you just look how the math

changes. And that just kind of

leaves me kind of flat. And there's no

connection to the real

physical world when you do that.

Whereas when you try a real physical

demo, you know, you eat

something up, you stretch something,

you bang on it, you do something to it,

you actually see it

respond. And it's hard to deny

that that's a real thing that just

happened. And so to me, physical

demonstrations are so powerful,

besides all the three things you just

mentioned, I think they're

just powerful because they

expand a student's everyday experience.

And I don't think everyday

experience should ever be

discounted. It's what we are, you know,

we grow up, we fall down and

it hurts, we run into a wall and

it hurts. And it's a real thing to

anybody who's experienced any of those

things. And unfortunately,

everyday experience doesn't always serve

us well. And that's kind of our job as

educators to explain

to students that, yeah, you know a lot,

and we really value what you

know. But there's a lot you

probably don't know. A lot of things you

haven't quite experienced

that we want to make you aware

of. Because if you can understand these

concepts and these ideas that we're

trying to teach you,

and start to believe it and start to fold

it into your everyday

experience, you're going to develop

a really high quality intuition that will

help you design things using the

fundamentals of material

science. It's kind of what we do. And so

doing demonstrations, I

think is just a critical part

of teaching material science. So at least

that's how I feel. I

never cared much for these,

the physics FET demonstrations or

JavaScript things because,

yeah, they're kind of cool, but

they illustrate certain things, but they

don't really add to that

individual experience. And I

think that's really special. Yeah, I

definitely have to agree on how important

students' individual

experiences are, both what they bring to

the class as well as what

they experience in class.

And this is where the right demo at the

right time can be so

powerful because of students from

their everyday life and from their prior

experience, if they have one expectation

about how a material

should behave and then they see it in

real time live in front of their eyes

behaving in a different

way, that's not what they expected. That

can be a really powerful

catalyst to get them to

evaluate how they understand the content

that we're trying to teach.

Right. Now, of course, the kind of demo

that you would choose

depends pretty much entirely on who

the audience is. So, you know, we've kind

of just been talking about

intro to materials courses,

because that's what you and I do the most

of the time. But there's a

lot of other audiences that

I think you have to tune the demo to the

audience to make sure they'll

be able to receive it and get

something out of it. You know, for

instance, when you go into a K through

six class doing outreach,

you're probably not going to show them

the zinc aluminum system

where you get this metastable

state and you smack it and it gets hot.

They would have no chance

of really understanding that.

On the other hand, liquid nitrogen ice

cream. Wow. That's a fun

thing for little kids to do. And

it connects with their everyday

experience with eating ice cream. And now

you can talk to them

about how you can change the texture of

that ice cream by changing

the kinetics of that experiment,

which is kind of cool. I love that

example, because that is

one that really does work at

all levels exactly as you described, even

for a young child, it's

ice cream. But then that can

go all the way up to an undergraduate or

even a graduate kinetics

course where you're looking at

the nucleation and growth of ice crystals

and how this is affected by

the cooling rate and by the

ratio of, you know, nitrogen to cream and

these other factors, it can

become very complex or not

as you want it to be. And that's

something that I think we should try to

aim for with all of our

demos is that they really do work at

multiple levels so that

we're not trying to create

entirely new suites of content for every

separate audience. And that's

great if we can pull it off,

but sometimes it's hard. You know, so

like a silly putty. Yeah, we do use that

to show viscoelastic

behavior at any level, but it's a really

simple concept, at least the

silly putty part. So that's

more amenable to K through six or high

school students, even

intro material students. But I

don't think we want to be pulling out

silly putty for a graduate course and

polymers. I think they

know that. But the other kinds of demos

that we do all the time, a lot of us go

into high schools to

try to get students excited about

material science so that they might

choose a materials career.

And so I know you've done a lot of this.

I've done some. And I think the most

exciting tool that we

can bring to high schools is the portable

scanning electron

microscopes. Maybe you can talk a little

bit about how we do that. Sure. The

future is an amazing place. You can just

take an SEM and carry

it around in the back of your car now.

And there are tabletop models made by a

variety of manufacturers

now that we've taken to classrooms, to

museums, to public

science centers even. And

you know, the power of that, this will

also connect back to your point about

virtual demos, I think.

One of the things that really makes

materials science special

is how we work across so many

length scales. And to be able to zoom in

real time from 10x to 100

to 1000 to 10,000 to 50,000,

and to see a single object at so many

different length scales

can really be a mind-blowing

experience and get people to think, "I

didn't even know that

existed." So I am very glad that

we have the ability technologically to do

that now and to bring that to people

instead of having to wait until they're

already in the university.

Especially when you show them things like

shark skin, because they

hear about the Olympics and

athletes wearing these shark skin bathing

suits for swimming, which

are outlawed now because they

work too well. But to show them what

shark skin actually

looks like, to show them how

butterfly wings are really diffraction

gratings, and that's why

you get all those weird colors

off the wings when they shimmer. Even

just showing them the width of Lincoln's

leg on a Lincoln penny,

because his leg is 100 microns wide, and

you can just barely see

that on the penny with your

naked eye, but you can really see it in

the SEM. And it just gives a way to

connect with real life

at all these different length scales. And

I think that's really

important for high school kids,

because they haven't really appreciated

that yet. Whereas college

kids and certainly graduate

students, they have. They understand all

that. But you can use the

same tool to do other things

for the graduate students, looking at

twinning and all this other neat stuff.

And then the other place we use

demonstrations is when we go to career

fairs or majors fairs,

where we bring things to try to get

people to come to our

table to come to talk to us.

So we have a shot at convincing them how

cool material science

is. And those are a little

different. I mean, I think the demo I've

always liked the most is

the one with the CD that you

squish in there, you spray that stuff, it

slams out. Things that

blow up or explode really get

the students excited. Maybe as soon as

there's a crowd, a crowd of

people with everyone wearing

safety glasses and loud noises happening,

and the whole room wants to

know, well, what's happening

over there? That must be the cool kids

table. So it can certainly be

a good way to rope people in.

That particular demo, how it works is you

have to acquire these

legendary artifacts known as

compact discs, they come from a previous

age. And if you can get

enough of them in one place,

what you do is you put the CD under some

flexural stress. So have a

mount that you can clamp it into

and squeeze it a little bit and spray it

with furniture polish.

And what will happen is that

the furniture polish will change the

cross linking between the

polycarbonate chains in the CD,

and it will reach the point where the

strength of the polycarbonate

changes, but it's still held

under this constant stress and eventually

it fails. And so the CD

will snap and jump out of

the holder into usually a few pieces. And

it's a really great way

to illustrate that chemical

stresses and chemical processing of

materials alongside mechanical stresses

are really important

to understanding processing and materials

properties. Yep,

that's a cool one. And then

finally, another really important kind of

demonstration for the materials community

is what we do with our teachers camps.

And you've been involved with the

teachers camps for years,

Tim, and maybe you can talk about, they

have a different set of

boundary conditions, right?

Things have to be cheap and they have to

fit into lesson plans. And

that's been pretty much the

hallmark of the whole ASM Foundation

teachers camps is showing

these teachers how to do these

demonstrations in class as part of the

curriculum. And so maybe you can describe

some of those for us.

Yeah, the ASM teachers camp, anyone out

there who's listening to

this, if there is one in your area

and you haven't interacted with it, I

would absolutely recommend

that. It's a great experience.

It is a good way to build relationships

within your community as

well. And also a good way to

pick up some good tips for your own MSE

classes. Here's a couple

examples. Many of them are quite

chemistry oriented. A lot of the schools

where these teachers are

teaching don't have a material

science class. They might have a

"engineering course." Some

have physics classes, but mostly

they're teaching chemistry. And so

they're approaching really material

science from the view

of what can a high school chemistry

student engage with. So they're looking

at crystal growth and

single replacement reactions. For

example, there is a demo that they do

where students take a

galvanized nail. They immerse it in a

copper, I believe it's a

copper chloride solution, and they

grow metallic copper off of this nail as

the copper replaces the zinc atoms on the

surface of the nail.

So that's a really great one. And another

example that we use all the

time at the college level as

college level is the iron wire. It's

truly one of the classic greats of MSE

demos, I feel. And Steve,

I know you use the iron wire in your

classes as well. So can

you talk us through that one?

Yeah, I love that one. This is of course

where you take a piano

wire, which is a very,

very low carbon steel, almost zero

percent carbon, and you stretch it out

and you do something you

tell the kids, "Don't do this at home."

And you take the two ends

and you plug it into a variac

and you just crank it up. And as the wire

gets hotter and higher,

of course you get thermal

expansion. But it's two effects that

you're trying to teach.

One is thermal expansion,

of course the other is the BCC to FCC

phase transformation of

iron. And so as it's heating,

it starts to get hot, red hot, and it's

sagging. But right when it hits the

transition to FCC iron,

because FCC is more close packed than

BCC, it's a volumetric phase

transformation. So it shrinks.

So it goes down, then it goes up, and

then because you're still

heating it, it eventually

expands and goes down. And it's really

obvious when you cool it.

So once it's glowing hot,

all the way down above, it's an

austenitic material, you just turn off

the variac and it comes back up

and then it drops down and then it goes

back up again. And most

students get the thermal expansion

part, but very, very few remember about

the volumetric phase

transformation, because that's

kind of a new concept for most students.

Most students, they come

into college and they've

heard of phase transformations. They know

you can go from liquid to

solid to gas, and that's it.

That's all you learn in high school. And

now we tell them that a

phase can be different

crystal structures. And that is kind of

very disturbing to them

because it's challenging what

they thought they understood. And now we

tell them that there's

more to it. And so what is a

different crystal structure? Well, there

are, you know, you can show them x-ray

diffraction patterns,

but I don't know if they're going to

believe that. But if you show them a

volumetric change and how

it's reversible, it goes up and down. And

then I tell them how when

I was a graduate student,

I used single crystal iron samples that

had to be very expensive

because you can only make them

with something called strain annealing.

So my little tiny sample

was like 800 bucks. And once

I made the mistake when I was sputter

cleaning it, you know, I had

two wires spot welded to it,

right? So I would heat the wires and it

would get hot. Well, I took

it up too high. I took it up

above the BCC and FCC phase

transformation. And yeah, it came back as

BCC, but it wasn't a single

crystal anymore. It was a mess. And my

advisor was very kind to me and said,

don't worry about it.

Just don't do it again. And he bought me

a new one. That's very nice.

But it's, you know, you get,

you know, those of us who do these things

in research, we get burned

all the time by our demos,

which brings up a really interesting

point about demos. You kind of have to

have a sense of humor,

because they don't always work. In fact,

it's very easy to have them not work.

Yes, they will betray you when you need

them the most. Right. And a

lot of that has to do with

the person who sources the materials,

puts it together, trains

the graduate student that's

going to run the demonstration. And often

the only way for that

person, namely you, to really

know that you have a handle on this was

for you to actually come to

class and do the demo yourself.

So you felt extremely comfortable that it

would work. Then you

would be in a position to show

somebody how to do it. For example, the

iron thing, it doesn't always work,

right? And it doesn't

always work. Because if you use one piece

of wire too many times, you

get all these green boundaries

and nano crystalline material, and it

just messes everything up, because those

green boundaries pin

the transformations. And so the trick for

that is to always

start with a fresh wire.

And so, you know, where do you learn

that? Well, by experience,

by doing it a few dozen times and seeing

when it works and when it

doesn't, and finding out what

the stopping points are another one, I

use this to get graduate

students all the time, because

another factor is how quickly you turn up

the temperature on the

wire, because you're feeding

at current, that's your heating mechanism

is dual heating. And the

resistance is a function

of the temperature. But often a novice

implementer of this demo won't be

considering the fact that

the resistance of the wire is changing.

And so they crank up the

current, and then it blows the

fuse in the variac, and then nothing

happens at all. And I did everything

right, what went wrong?

Well, you forgot that the resistance is

lower when it's colder, and

you fed it too much current,

and the fuse couldn't handle it. But if

you ramp it up slowly and let that

resistance go up as well,

then so there are so many little

subtleties like that that, yeah, you

should if you're bringing a

new demo into your class, I would no

kidding recommend

practicing at least a dozen times

before doing it in front of the students

if you want to have a

good chance of success.

If you want to model is how to handle

things going wrong, oh, yeah, jump right

in and give it a go,

something will go wrong for sure. But

usually we want more than that.

Another favorite demo when you want to

show strengthening of

metals, you take a pretty much

pure aluminum bar, and you anneal it. And

then when you anneal it

pure aluminum is very soft,

you can bend that bar very easily. And

then hopefully when you

bend it, you've introduced

enough dislocations that it's very

difficult to bend it back. And so it

sounds great in principle.

But I can't tell you how many times that

demo hasn't worked.

Either the bar wasn't annealed

enough. And I could barely bend it to

begin with. You'd like to do this by

asking someone who thinks

they're really weak, but would like to

demonstrate they can bend metal, they

have them come up. And

if they can't bend it, oh my god, it just

ruins the whole thing. Yeah.

And but the other problem is

if it's too annealed, yeah, it's easy to

bend. But then the strong

people in the class can actually

bend it back. And that again, takes your

thunder away because you

want it. I mean, I'll never

forget. I had one bar that was perfect.

This very weak individual

was able to just bend it.

It made them feel great. And then I said,

anyone think they're a

really big strong guy,

you know, guy or girl, and this Marine

came up. Oh boy. And he

just, he couldn't bend it back.

And I thought he was going to kill me. I

thought he was going to,

because he was so embarrassed

that he couldn't bend back and he was a

Marine. And so I was like a little

fearful, but that was

exactly what you want to happen. So how

do you hit that just right?

And the only way to really do

that is to have enough bars so you can

try one. And so if I've

learned anything about demos,

it's all the things that can go wrong

with a demo and it's going

to happen. And you're just

going to have to explain to the students

that this is real life,

you know, it's complicated

and lots of different things happen. And,

but luckily the

something you said earlier is so

true. What really is important is that

students make a prediction

before you do the demo. And I

believe Eric Mazur has written some

education research papers

demonstrating this and showing

that if the students can predict what's

going to happen before it

happens, it doesn't matter if

they get it right or wrong because

they're roped in. Once they've made a

prediction, they've got

skin in the game. They want to know

what's going to happen. They

want to see if they're right or

wrong. And so they end up paying much

more attention and then

they want to understand why.

And so as long as you can produce a good

reason why, even if the

demo doesn't work, if you can

tell them why it didn't work, they'll

actually learn a lot. And

ultimately our job isn't to make

the demos go great. Sometimes it's good

they see that we fail all the time

because that's normal,

not the other way around. But what really

matters is that they

learn the concept and bring

something into their everyday experience

that they didn't have before

to give them the ability to

think about how more complex things might

happen in the future. I

couldn't agree more. What are

some other greatest hits that we have?

We've talked about a few metals ones. Oh,

a lot of polymer ones.

Yeah. I know one polymer demo that I

really like because it also brings in

functional properties

a little bit is making polarizers. That's

something that's very low

cost, very easy to do, and looks

really cool, but also reminds students,

"Hey, there's more to life

than strength and Young's

modulus and things like that." Right. So

which one do you like? So I've

tried it a couple of different

ways. I've found the best results with

garbage bags actually.

Polyethylene garbage bags. Yes,

polyethylene garbage bags to be clear.

Well, also to be clear. But the trick

with those is getting

the strain rate right so that you can

strain them far enough to

get some good alignment of the

polymer chains to build in that

anisotropy. So they become polarizing

without actually tearing

them. And that can require a little bit

of a delicate touch, but

it's one of those things

you practice it. And as soon as you get

it right the first time, you

say, "Ah, that's what I have

to do." And it's pretty repeatable after

that. But it's also something you can

have a whole class to

buy a box of garbage bags. No big deal.

Right. But you know what I find the most

challenging part of that is to demo that

in front of the whole

class. They got rid of all

the overhead projectors. Right? That was

the perfect place to demo

it. So if two people held

polarizers, right, show that when you

cross them, it goes black and

open it up. And with those two

people holding those, another person

would come in and stretch the

polyethylene garbage bag and

then rotate it. And while it's not as

even as a polarizer, you can

definitely see all the changes

in the intensity on the screen. But they

got rid of that. And

document cameras don't quite cut it

because not enough light goes through.

And so it's a little harder to do. So I

wish they'd bring back

some overhead projectors just for that

demo. Those things were

great. The other one I really like

is how you can have students feel

entropy. And that of course is

the rubber band one. Have you

seen that one, Tim? Oh, yeah. And so it

turns out that your

forehead is very, very sensitive to

temperature. So if you take a rubber

band, you pull it, stretch

it. And then you know, if you

pull it really quickly and put it to your

head, it feels hotter. And

why is that? Because all those

elastomers are sliding along each other,

creating friction, and

it's getting heated, just dual

heating, right? But then if you take your

stretched out polymer and

you release it very quickly and

put it on your head, it is noticeably

cold. Cooler. Yeah. It's

colder than your ambient was.

And why is that? That's because all those

ordered chains have disordered

and entropy and temperature are

intrinsically related. And so you can

feel entropy. And what

I like about this one is every single

student gets to do the demo

themselves, which is ideal.

Unfortunately, with large classes, we

can't always do that. But

with rubber bands are so cheap,

you can pass them all around. Then you

see everybody pulling

these things and it's just

clicking it on the floor. And you know,

entropy is a hard concept to understand.

And hopefully this will give them some

insight into it. And the

very fact that polymers are

these big chains that are either ordered

or disordered, it should

work. And that's one that

almost always works. The other demo I

really like is when you

teach fatigue. So fatigue is

very statistical in nature. It's not

very, what's the word? It doesn't, oh,

there's a word for this.

It doesn't follow from first principles,

right? It's not

reproducible in the way that,

you know, the number of dislocations when

you strain something might be. And

it's, there is a lot of noise and it's

because the origin of fatigue

is a flaw. And you don't know

what the flaws are or how they're

distributed in the material.

So when you stress, even though

you're doing it well below the yield

stress, you're still accumulating defects

and accumulating and

changing internal flaws, cracks, all of

this stuff. So finally,

when you do it too much,

it catastrophically fails. And that's why

fatigue is so dangerous. So

little things like when, you

know, you teach mechanical properties,

you want students to

understand how to calculate an

appropriate safety factor. And it's

usually pretty easy. You

choose at least two, maybe 10,

and you just multiply, you know, the

expected maximum yield

strength and stress that you're

going to have on it and you're done. You

can't do that with fatigue because for

fatigue, you need to

understand the probabilistic nature of

how it fails. So those SN

curves, those are just the 50%

line curves. What really matters is how

all the data is collected

and how it distributes. So the

90th percentile, how far away from that

50% line is that? And

that's going to be different for

different materials, different processing

conditions, it's complicated. So to try

to illustrate that to

students, we give them paperclips and

make a quarter of the class

bend at 90 degrees and back,

that's one cycle, and they keep doing

that. And each person reports

their own number of cycles to

failure. Then the next quarter of the

class does 180 and back, 180 and back.

The next one does 270,

and the last group does 360. Well, the

360 group, of course, those

are going to fail much earlier.

But you're also going to get a much

bigger spread of the data. And when we

look at the raw data,

we can show the students using the class

collectively how much

spread in the data there is

and how that spread changes for each of

these different, well, we

call them loadings. It's

really not quite fatigue, but it's a

strained version of it.

And I think that's a really

valuable thing. And it helps them

understand that. The other demo we do,

it's gotten a little,

what's the word? It's what we used to do,

we don't do anymore, because

some people get embarrassed.

We used to do ask everybody to report

their weight in pounds. And

even though it was anonymous,

people got upset about it. So now we do

height. We ask everybody to

report their height in inches.

And then we show the height average and

the number average

difference of those sets to talk about

polymers with different lengths of

change, just to show them

that you get different results,

depending on how you count and why it

might be important. So

those kinds of demonstrations,

those are still participatory, they might

not be physical, but you're still

illustrating a point.

That's important. One demo I'd love to

do, I don't know if we can pull this off,

but it's the DaVinci demo. Do you know

which one that is? No,

what's that? So Leonardo DaVinci,

way back when he was alive, he did

experiments and he proved

that ropes that were longer

were weaker than ropes that were shorter.

And this usually

blows our students' mind,

you know, the ropes are the same. But of

course, it was because

of Weibull statistics.

And Weibull statistics is just weak link

theory. So the longer a rope is,

statistically, you're

going to have more flaws in the longer

rope, bigger flaws, leading to it

failing, because you'll have

a better chance of a weak link and a long

rope than a short rope.

And DaVinci did that. That's

pretty cool that he did that. And so it'd

be really fun if we had

like some really long ropes

and enough heavy weights to actually see

them break. It would

probably get expensive and take

a lot of space up. But it's kind of a

cool thing that he did that well before

Weibull did his Weibull

statistics. Yeah, that would be an

interesting one to try to turn into a

full class activity,

it'd be a matter of testing out different

types of ropes, different

amounts of weight, so on to

figure out what gives results that are

sort of messy enough, but

still work. And we kind of do

that with one of our projects we do in

our MyIntro class, because I

don't give exams, I have a lot

of time, and because I don't lecture, I

have a lot of time. So for

the part of the class where we

cover mechanical properties, my project

is to build a mechanical testing

instrument out of garbage,

you can't spend more than five bucks. And

so students are

constantly, you know, taking thread,

or taking a laffy toffee and clamping

things to them and looking how it

stresses or strains or

breaks. And it's a lot of fun. And that's

another way to have students

come up with their own demos

is a really fun way. And then of course,

they have to explain to

experts walking around the room,

why it happened. But it's just more

engagement, and it's more

physical. And again, it just

helps the student understand in a

different context than just reading a

book and doing homework

problems, how these phenomena actually

work, so that they can

use the concepts that we're

trying to teach them for whatever they do

in the future. So what other demos?

You've worked on a lot

of demos. I don't know if you have the

list I just gave you, but you can talk

about some of those.

Yeah, I suppose we should round out with

a couple of ceramics

oriented ones. So the first one that

comes to my mind, I love this. This is

also one that requires a

little bit of finesse. But it is

glass the conductor, I learned this one

from the ASM teachers camps,

actually, I've gotten several

demos from them over the years. And the

way you have this set up is

that you've got a light bulb,

and you have an open switch, essentially

in the circuit feeding the

light bulb, and you bridge

that switch with a glass rod. And of

course, the light bulb

doesn't light up because glass is an

insulator, allegedly. But what people

often forget is that

processing is really important.

And the the demo, what you do is you heat

the glass rod with a blowtorch.

And as it gets hot enough, the mobility

of the sodium ions in the

glass, so you do want to use

soda lime glass for this, it'll have a

higher density of sodium

ions in it, they get enough

mobility to where they can actually carry

enough current to light the

light bulb. And if you really

nail it just right, you can actually get

it to self sustain as well

where you take away the torch,

and the resistive heating from the

current passing through the glass will

keep the glass hot enough

to keep the mobility high enough that

current can keep flowing. And

the the ASM master teachers who

have done this a zillion times, I've seen

them keep one going for

something like 20 minutes before it

finally petered out. But yeah, conducting

electricity through

glass with the application

of just a little heat, that's always a

winner for me. Well, and it's also really

important to explain

to students that it's not just electrons

that transport charge,

right? Many things can transport

charge, it's a charge carrier, not an

electron. Some things are

holes that are the dominant

carrier. Some things are ions, like in

the example you just showed,

sometimes they're solitons,

you know, double bond flipping, that make

things move. So it's

the fact that the ideas of

conductivity and resistivity are very

general, and they span across many

different kinds of charge

carriers. And that's a really important

thing to get students to

understand. So it's great for them

understanding glasses, but it's also

great for them

understanding electrical properties.

Yep. What about the making copper for

malachite? That's another ceramics one.

Oh, yeah, rocks are ceramics after all.

There's this is one that is

so fun to do with students,

partly, of course, it involves smoke and

fire. And so that's

exciting. But it's a really great

illustration of this very, very old

process of turning rocks into

metal. This is, I don't know,

5000 years old technology at this point,

and still quite relevant

today. So how it's set up

is that you get a piece of charcoal, not

like a brick hat, but a

good lump hardwood charcoal

large piece. This is your carbon source.

And you can carve or drill a

well, you're making a crucible

right in the charcoal, and you load it up

with some flakes of

malachite. And you heat it. Again,

I use a torch. And as you heat it, you're

going through a series of

chemical reactions, where

you are making carbon monoxide and carbon

dioxide as you as you make

the charcoal react with the air.

And then you have the reactions between

the malachite, which I'm

trying to get this from

memory, I think it's a copper carbonate

hydrate, maybe. But you are you're

dehydrating the rock,

and you're also de carbonate thing.

That's not a word. But you're

pulling the carbonate out of

the rock, as it reacts with the, the

carbon monoxide, and the

oxygen in the air in this

hot air that you're making. And what you

end up with is nothing left

but the copper. And the way

it looks visually, it's hard to describe

this in words, but you

start with this green rock,

and you heat it, and it gets glowing hot.

And students are like,

Okay, is anything happening,

you're just making the rock glow because

it's hot. But then

after a couple minutes,

you take away the flame, and you let it

cool down. And it's

still red. And they're like,

Why is it red? Well, you tell me, you

took high school chemistry, what is a

color change indicate,

and they're like, Oh, chemical reaction.

So we go through this. And

then I pull out these little

red rocks that I've made, hit them with a

hammer, and they don't break. They're

ductile, they smoosh,

they smear. And so then it's just another

one of those, huh, I

thought ceramics were brittle,

what happened? And eventually someone is

like, Oh, it's red because

it's copper, you turned it into

a metal. Yeah. So wonderful demo. Love

that. I learned that from

Kevin Jones actually props to

him for being my inspiration on that one.

But yeah, I love that for

sure. I even like if you

watch carefully, once it turns to copper,

the flame from the

blowtorch, you start seeing little

bits of green green, because you may

remember from your inorganic chemistry

lab course, that the color

of the gases tell you something about

what materials are

there. So it's kind of cool.

Anyway, there are tons more demos. I

think we're out of time. I

just realized this. We're at the

45 minute mark. Oh, my goodness. So talk

about demos all day, but I

won't, we should wrap it up.

So we'll wrap this up and let me play our

outro music. So with

that, thanks for joining us.

And we'll see you next

time. See you next time.