Hello! So today I’m going to talk about my favorite subject chemistry, and how everything in the world is made of elements, which are assembled into molecules, and then set in motion by chemical reactions.
Elements are the pure substances, from which everything else is built. You can’t divide an element into anything simpler, and when you put them together, you get everything. Every element is unique. Every element has its own story .But first a little bit of my story.
I first became interested in elements about 15 years ago for a completely silly reason.We needed a table for my office. In English you can make a joke about the periodic table, because in English the word “table” means both the thing that you sat at maybe you have dinner, and it also means when you write a bunch of numbers together on paper. So you see “periodic table”, that is funny in English, not in Chinese, but, you know.
So it was a joke, I made a “periodic table” table. And then I thought, well, you know, I have a periodic table table, I should put elements on it. So I started collecting elements and I just kept going.
And it became unreasonable. I had too many elements, I didn’t know what to do with them all. So I thought I’d better take a picture of everyone, and I should write a little bit about a little story about where these elements come from, because otherwise I’ll forget what they are.
So I wrote all these descriptions to the pictures and I made a website, where I put up all the pictures and all the stories. And then just a month or two later I got a phone call from the editor of Popular Science Magazine which is the largest circulation science magazine in the US.
And they said, “Do you want to write a column every month about elements?” I thought, “I don’t know. I’ve never done that before.” I have no idea, but you know, whatever.”
So I spent the next ten years every month writing something about some element or something to do with chemistry. Basically because we needed a table in my office, that was the only reason. So that became two books, Mad Science, Mad ScienceⅡ, Both which are available in Chinese, which is very nice.
Then I made a better website, periodictable.com, and it looks nicer and better URL. Eventually I wrote a book about elements, because I figure out that I have enough stuff now, I’ve written enough about different elements and I could make a book. That was 8 years ago? So that book has now been translated into 25 languages, which I just can’t believe that! It’s amazing!
Including Chinese, something like 6 years ago. When you write a book, you are forced to learn a lot about many things. So I learnt a lot about elements in the process of writing this book. And I also learnt a lot about myself.
For example, iron. You know, there’s not that much to learn about iron. Iron rusts. Everybody knows that. You don’t have to study it. But what took me a long time to realize is why iron makes me so sad all the time. I don’t like iron. The reason is because of rust.
Rust is death, and dying, and decaying, and the end of things. Every car, every bridge, every iron fence … everything made of iron is dying slowly, is rusting away. And this is very sad.
Actually there is a very nice song by a popular folk singer in America named Arlo Guthrie that has beautiful line about iron in it, about iron rusting. So I’m gonna play you a little bit of that song. So there is “the graveyards of rusted automobiles” exactly like in the song, very sad.
I love that song because it is a song about the train, and the name of the train is City of New Orleans. That train goes right about mile away from my house. That train goes right about mile away from my house. You really can get on that train and it will take you a thousand miles south to New Orleans, and the whole time you will see rust everywhere.
So a rusty hammer, this to me is a sad thing. A titanium hammer, on the other hand, that is a wonderful thing. Titanium is a beautiful element, it’s strong, it never rusts. It will last forever. And it will be beautiful forever. These are crystals of 99.999% pure titanium, grown from the gas. I mean, just look at it! There’s no more beautiful element!
In fact people often ask me, what is my favorite element? I don’t really like this question, but everyone wants to know. Sometimes I just say, “well, titanium, because it doesn’t rust. And it’s beautiful, it’s shiny and it’s strong.”
But really, the fact is that every element has some reasons why it’s nice and good and beautiful. So for example, sodium. Sodium also is shiny, right here, but that’s not why sodium is interesting. What’s really cool about sodium is that you can throw it in the lake.
This is some video from a sodium party that I had a few years ago, where basically I invited a bunch of people, sometimes there is sound. And basically when you throw sodium in the lake and it explodes, and that’s great.
One thing is nice about it is that it is a way of sort of bringing people together and showing them the power of chemistry. What you can do if you know a little bit about the chemistry. And that’s fine. So I like sodium because it is a way of bringing people together and which brings us to the next part of my talk, which is bringing elements together to the next part of my talk, which is bringing elements together.
Let’s say we start with four elements. We have Hydrogen, which is an explosive gas, burns very fast. We have Carbon, which is diamonds or graphite. We have Oxygen, which is another gas that we need to breathe, we die without oxygen. And we have Chlorine, which is a gas that will kill you painfully and quickly, very dangerous stuff.
What do you think we get if we combine all four of these elements together? Well, you get a molecule. That is what’s called when you make chemical bounds between elements. There’re millions of different molecules that you could get by combining those four elements. Some of those are poisonous molecules and some are very boring and good for anything. Some of them are harmless. Some of them taste good.
This happens one of them taste good. It’s sucralose. Sucralose is an artificial sweetener, a synthetic chemical. That tastes sweet to us. It’s used in many baked goods, in chocolates as an artificial sweetener. It’s interesting because it is completely synthetic and doesn’t exist in nature, yet it tastes very good to us.
Here’s another example that chemical tastes good to us. This is sugar. Ordinary table sugar that comes from sugarcane, sugar beets. It’s a natural chemical, and it’s sweet. But actually it is not very sweet by standards. This is about 45 kilograms of sugar. And it’s 170000 calories, 14000％ of your recommended daily energy in take.
But you see the little thing on the very top. The tiny little dish up there in the yellow zone. So this is four and a half grams of neotame, which is another synthetic chemical. It is the most intensely sweet, commercially available artificial sweetener. That four and a half grams is as much sweetness as the entire 45 kilograms of sugar. How intense is that！
Here’s a comparison that I really love. Suppose the neotame were as poisonous as the most poisonous-known synthetic chemical, which is VX nerve gas, a chemical specifically designed to be as poisonous as we could possibly make it. If you were to use that, you know, incredibly poisonous version of neotame, and sweeten a cup of coffee with it to a reasonable level of sweetness, and drink it, you will probably be fine.
It’s well below the lethal dose, because even it’s as poisonous as the most poisonous-known synthetic chemical, poisonous-known synthetic chemical, you still don’t need enough of it to be sweet enough that it will actually be likely to kill you.
I think that’s amazing and one reason I don’t worry about artificial sweeteners because they are so little used when you put them in your food, that it actually will be difficult to design one that will be harmful. So that’s the example to molecule.
I find molecules very interesting, and I think something is interesting, apparently I will write a book about it. So I’ve written a book about molecules, which is also available in Chinese. I’m going to talk about a couple of molecules, here’s one of my favorites, because how useful it is in my other projects. And because it helps understand how molecules work in the world.
This is cotton. If you pull a fiber off a piece of cotton off a cotton plant, it’s about 2 or 3 centimeters’ long. It’s very short. This is five kilometers of cotton thread on a commercial spool. All the fibers in there are still only 2 or 3 centimeters long. This is five kilometers of cotton thread on a commercial spool. All the fibers in there are still only 2 or 3 centimeters long. They are not glued or knotted or tied or anything like that, they are just twisted around each other.
And if you untwist cotton fibers, you can actually take it apart, without breaking any of the fibers. You just untwist them and they come apart. This turns out actually to be quite a good way of thinking about the way certain polymers a certain kind of plastics work. Plastics are made out of long thin molecules. Just like cotton fibers that are made out of long thin fibers. You can actually sort of understand how plastic behaves by thinking about the way that thread behaves.
So this is an ordinary grocery bag, like you get from the store. You can pull it apart pretty easily. It just separates. And when you do this, you’re probably not breaking very many of the molecules. Just like when you untwist the cotton thread, you are not breaking the fibers.
You’re just separating them from each other. But if you instead pull it and sort of stretch it until it gets longer, it kind of becomes like a fiber almost, you will feel, you should try this at home sometime, you will feel a certain point, that’s the point of which molecules all become elongated and line up with each other.
And they are sort of twisted around each other and they can’t slide any more. When you reach that point, you actually feel a bounce. It’s sort of a little bounciness to it. That’s the carbon-carbon backbone of those long molecules pushing back at. Those bounds are very very strong. They are much stronger than the bounds, the forces, that are holding together the polymer molecules. So it is a very nice way of seeing a sort of molecular level of thing that you can actually feel.
So cotton again, cotton, it’s made of molecules called Cellulose. Like all polymers, there’s many units repeated over and over again. This is one unit there. So what is the molecule that repeated many many times in cellulose? Well, we’ve seen that before, just a minute ago. The unit is actually Glucose, it’s sugar. Cotton is made of 100% sugar. So why doesn’t cotton taste sweet? Why don’t we eat cotton?
Because if you want to get the sugar energy out of it, you have to break it up into individual sugars. We don’t have any way of doing that. We don’t have any enzymes in our stomach that can break up cotton. Only certain bacteria can do that.
So if you want to get food energy from cotton, you have to feed it to cows. And then eat the cows. This form of chemical processing is that we called cattle ranching .So now you’ve learn something. This is two kinds of cotton. One is regular cotton. The other is cotton candy. They are both made of 100% sugar. It’s just that sugar is bounded together in a different way between the two .So back to sweet things.
These are four examples of non-sugar sweeteners of high intensity sweeteners. Two of them are natural products from plants. And two of them, the two smaller molecules are synthetic chemicals. They taste better than the plant extracts.
But what people usually worry about is whether they are healthy or not. Should I eat them? And I think this is really the wrong question. It’s not a question of synthetic verses artificial you should be asking. You should really be asking is that is this a good chemical or bad chemical, not where did they come from.
The fact is that there are good and bad synthetic chemicals, and there are good and bad natural chemicals. This is an example of bad synthetic chemicals, lead acetate. It’s terrible, poisonous. It was used as an artificial sweetener by the Romans. And it poisoned them with lead. It was not a good idea.
This is an example of bad natural chemical. It’s Gycyrrhizin. Apparently black licorice is not popular in Chinese. But this is a very popular candy in the US. The taste of licorice is gycyrrhizin. And it’s very poisonous.
If you eat 100 grams of black licorice a day, which is a lot, but not impossible, for a few months, you can have irreversible liver and kidney damage, heart damage. It’s very poisonous. If it were synthetic, it will never be allowed. But because it is natural, there’s no regulation and people can put as much as they want in their food. Because natural verses artificial is the wrong question and what we should be looking at was poisonous or not poisonous.
The fact is that of the four most poisonous-known chemicals, three of them are natural. It’s only the fourth-most poisonous VX nerve gas, that’s synthetic. Nature is much better at making poisonous chemicals than we are. The other thing to remember is that all of us like the taste of chemicals. The other thing to remember is that all of us like the taste of chemicals.
If you like asparagus, that is favorite of mine, I really love asparagus. And if you like asparagus, those are the chemicals that you like the taste of, and that you enjoy eating. All food is made of many many many chemicals. Some of these are poisonous, some of them are not. Some have flavor, some are for killing bacteria, or fungi, whatever.
You know, we really want to evaluate each chemical in its own right as a good or bad thing without really worry about where they came from. So at the beginning of this talk, I promised you the whole story of chemical, of chemistry. So we have elements, we talked about molecules, now it’s time for reactions.
I’m gonna show you a somewhat random collection of different reactions. This is one of my favorite reactions of all. We start with two main ingredients, aluminum powder, which is a pure element, and iron oxide, which is a compound of iron and oxygen. You mix these things together, you pour them in a concrete pot, and you light it, and then this happens.
So what’s happening here is that the aluminum atoms are stealing oxygen away from the iron atoms. You are getting a lot of heat released, a lot of heat released. At the end the result of this reaction is aluminum oxide because the oxygen is moved over to aluminum from iron, but not just any iron, what you get is white hot liquid iron. And just in a few seconds if you watch the bottom down there, you’re gonna see the iron come out.
That’s liquid iron. It was produced by the reaction and is now pouring out the bottom of that pot and here it’s going into the mold ,So why are we doing this?
It’s fairly elaborate procedure and a lot of energy is released. The answer is…so this is what that looks like after the mold has been removed. The thing you see in the left and right side there are two ends of train track. This is what it looks like after it’s cooled down and it’s been ground and polished. This is actually how high speed train tracks are joined to each other.
All around the world, they use this chemical reaction as a way of creating enough liquid iron to fuse, not just weld together, but actually melt together two ends of train tracks. When you go on a high-speed train, and it’s very smooth when you’re going on. You don’t feel any bumping. It’s because all the tracks has been melted together into one continuous piece. So it’s a very useful chemical reaction.
But really the reason that I like it is because it is the exact chemical opposite of rusting. Rusting is iron combing with oxygen to form iron oxide. Thermite is iron oxide being pushed back into iron. So it’s unrusting the iron, which is cool.
This is another example of metal burning, rusting very fast. In this case, lithium metal combines with oxygen, the same kind of reaction as rusting, but faster. You can actually make iron rust that fast. This is just an ordinary steel wool, you can buy it in the store .If you light it, it will burn!
And the reaction that happens is exact the same reaction slightly different mechanism but same reaction as rusting. It’s happening so fast that the heat makes the blow up like a glow like that. The key to burning is always oxygen. So you can do fun things with liquid oxygen that this is just ordinary charcoal with drops of liquid oxygen dropping into it until it flares up. A particularly beautiful demonstration of that is if you drop charcoal powder, this is a glass that’s filled with pure oxygen gas, so when the charcoal falls into it, suddenly it will brighten up because it is getting more oxygen.
But even the oxygen in the air is plenty to burn rapidly like that, if you have very very fine powder. The powder that we’re seeing here, is lycopodium powder. It was the favorite of the alchemists, the ancient magicians, that you will have a handfull of it, throw it in the fire, and there is big fire balls. And the emperor will be very impressed and think you are powerful wizard.
And really it is just actually the spores of club moss, it’s a moss spore. But it’s so fine that it makes beautiful fire balls. I like this particular sequence because we got several very nice photographs to use in the Reactions book.
I’m showing you a bunch of them because lycopodium is my favorite powder, and the kid was great in the photo should also…Beautiful powder, very much recommended.
So here is an example of a beautiful chemical reaction that it looks like burning but there’s no oxygen involved. It’s a reaction of aluminum and bromine to form aluminum bromide. But really I’m showing you because I think it is the most beautiful reaction that I’ve ever filmed.
It’s not really that interesting as a reaction, but it is very pretty. Here’s another very beautiful reaction, which is not burning. Your chemistry teacher may have done this for you students, that it’s a reaction between potassium iodide and lead nitrate. The result is lead iodide which is a beautiful gold color. This demonstration is sometimes is called the golden rain demonstration.
If you do in the beaker, because it looks like golden rain drops falling down. But it will be a very bad idea if that sort of “rain” would have fall on your farm, for example. Because it’s lead iodide, it will poison your farm field for generations.
So, really, when I think about chemistry, what I think about is fire, and that’s mainly because fire is so interesting. And human have always be drawn to fire. It’s everywhere. It’s even in an orange peel.
Look at that. I mean, you get an orange peel and squeeze it and you get a beautiful fire ball. The best fire, of course, the best chemical fire, is what in my Reactions book, I refer to as the ancient Chinese art of chemical arranging, which is of course, fireworks.
Fireworks are just different chemicals, gun powder, flash powder, stars, with different elements, for color, arrange just right carefully by a master. You get things like this. And you know, this is chemistry.
This is what chemistry is about. This is beautiful explosion of fire and beauty, which we see everywhere around us, but quite literally in the art of fireworks. So thank you very much for coming to see what I have to say.