Subtitles section Play video Print subtitles For us, life unfolds on human scales. Miles...feet...inches. But beneath the surface of things is another realm a billion times smaller than we are. A dimension that holds the secrets to understanding our world. What makes steel strong... ...why ice cream is delicious... ...what makes life possible. Secrets that help us create what we imagine. "The human creativity of chemistry. There's just nothing more beautiful than them." This is the realm of chemistry and these are it's greatest discoveries. Ancient Greek philosophers believed there were just four elements; earth, air, fire and water. And that air was the underlying element. A single substance responsible for the make up of everything in the world. Centuries later Leonardo Da Vinci was among the first to suggest that instead of being an element, air might consist of two different gases. It remained a mystery until our first great discovery. England, the latter part of the eighteenth century, clergymen and sometimes scientist Joseph Priestley conducted a series of experiments searching for new 'airs' what today we call gases. To find out more about what Priestley was up to, I paid a visit to Arnold Thackray. President and historian at the Chemical Heritage Foundation in Philladelphia Pennsylvania. "Priestley wrote and wrote and wrote on every subject that you've ever thought of. He wrote about history, he wrote about religion, he wrote about politics, he wrote.. "Science?" He wrote about science endlessly and Priestley was the man who knew everything. He would tell you the practice of it, the history of it, the theory of it and he was quite literally the man who knew everything." But along with everything else Priestley did this famous experiment right? "That's exactly correct, and there are two things that go into that experiment. The one is Mercury. This strange substance that's simultaneously a liquid and metal. And that's just crazy. Who ever heard of a liquid metal and so it was really puzzling. What is this thing? People were fascinated by it and so they wanted to explore it. Of course the other thing that went into it was the technology to deal with gases and here in Priestley's experiments and observations on different kinds of air we have the technology of collecting gases over liquids. "In tubes that you can see through." Exactly, so you can see the gas, you can see what's happening to the gas and now you really are in business. What Priestley does is he takes a burning glass to give it heat, a lens. He focuses it on this orange powder, the mercuric calx, he heats it, it changes into this metal mercury and a gas comes off. But Priestley doesn't really realize what it is that he's found." The answer would emerge in 1774 after Priestley paid a visit to Paris and shared the story of his discovery with another scientist... Antoine Lavoisier. "Paris is a marvelous place for Priestley to visit because Antoine Lavoisier is in Paris, talk of the town, doing the work that will end up as his elementary text on chemistry. And Lavoisier who is also mucking about with gases, hears what Priestley has done, is fascinated by the report of this new air, decides he'll repeat the experiment. He has lots of apparatus, better apparatus. He's a meticulous experimenter. And among other things he weighs things. Lavoisier, by weighing says something is being emitted. He calls the thing emitted oxygen. He rewrites a whole script of chemistry and he creates a list of elements that we still use today; Oxygen, Hydrogen, Sulfur. You can correctly say Priestley discovered Oxygen but Lavoisier invented it. So with Priestley's experimental work on gases, with discovery of Oxygen, with Lavoisier's articulation of a system of language, we have the whole conceptual scheme in which Nineteenth Century academic work is built. Twentieth Century industrial innovation. We have pharmaceuticals, we have biotechnology, we have cell phones. "Plastics?" We have plastics. That's exactly right. And all these things begin with the discovery of Oxygen. That's where it starts. "That's a lot to breathe in". In the early Nineteenth Century a British school teacher named John Dalton was hard at work pursuing his fascination with chemistry which would lead to our next great discovery. Dalton's experiments showed that the known elements such as Oxygen, Hydrogen, and Carbon combined in definite and constant proportions. From his calculations he hypothesized that the elements must be made up of smaller invisible pieces of matter with relative and distinctive weights. He called these pieces of matter atoms. "So, what did Dalton discover?" Dalton's great discovery was what he called the 'relative weights of ultimate particles'. "Ultimate particles." That's what he called it. It's a lovely phrase. Later on when he went public it becomes atomic weights. We know it as atomic weights. but it was ultimate particles. "So he used the word atoms?" He used the word atoms, the idea of an atom of course goes back to Democritus, the problem is, it's an idea. Is it any use? And Dalton was the man who made the idea useful. That was his great contribution. "From his work, Dalton developed what came to be known as his Atomic Theory. A revolutionary new system that defined the relationship between atoms and the elements. And it's an enormously simple system and Dalton thinks very simply, very visually. Here are the elements, here are the weight of the elements. Here are the complex molecules, and it's a wonderfully effective system. It connects the thing that chemists can do, weigh things in balances with the things that you can't see; the ultimate world of atoms and that's genius. How important was Dalton's discovery? His Atomic Theory helped generations of scientists further unravel the mysteries of the atomic and molecular world, including our next great discovery. In the early 1800's French Chemist Joseph Gay-Lussac was conducting a series of experiments designed to study Dalton's Atomic Theory when he observed something odd. When he combined equal volumes of different gases, and measured their reactions, the gases often produced twice the volume than he expected. How was this possible? The answer was provided in 1811 by Amedeo Avogadro; a physics professor at the University of Turin in Italy. While studying the results of Gay-Lussac's research, Avogadro had an insight. At the time, it was believed that gases were made of single atoms. Avogadro realized this assumption was wrong. The gases were made of multiple atoms. What came to be known as molecules. The realization that atoms could be rearranged to form molecules was the breakthrough that enabled scientists to move out of the chemistry dark ages and begin systematically creating new compounds. Our next great discovery occurred in the Nineteenth Century when many chemists believed that organic substances from organisms or living things were somehow different from inorganic substances from non-living things, but that was about to change. In 1828 Friedrick Wohler was working in his lab when something caught his eye. Wohler had placed two inorganic chemicals in a beaker; Potassium Cyanate and Ammonium Sulfate. Now when he looked at the beaker it contained a grams worth of small white needle shaped crystals. What made this remarkable was that Wolher thought he had seen these exact same crystals once before, but with an important difference. Those crystals had been organic. He had crystalized them while studying the chemistry of various substances found in urine. To make sure he wasn't mistaken, Wolher analyzed the new crystals. There was no mistake. These crystals were the same as those he had isolated before. He had made urea, which was something that had come out of a living thing. He had made it out of inorganic substances. Later he said in a personal letter not in the paper that he wrote about it that I have made urea without a kidney. He knew what he had done. "Meet Roald Hoffmann, winner of the 1981 Nobel Prize in chemistry for developing a theory to explain organic chemical reactions. So why is this discovery of artificially making urea? Why is that a great discovery? You know there comes a time when you need a discovery and it's sometimes a single one to cross a border, to break down a wall. This is what this discovery was. It's not that it was so important in and of itself but at the time that it came, the simple making of urea out of two inorganic chemicals. When it came, it caught people's attention. The whole story of the discovery is about the underlying basis, the building blocks of all matter, organic and inorganic being the same; atoms. If these lego bricks had existed in the early part of the Nineteenth Century, chemists could have used them to help illustrate something they were seeing in their experiments. A phenomenon that led to our next great discovery. The atoms of particular elements such as Sodium and Chlorine seemed to combine with each other according to fixed ratios. It was this combining power of atoms that inspired German chemist August Kekule to develop a system for visualizing the chemical structure of various molecules. Kekule represented the atoms by their symbols, then added marks to indicate how they bonded with each other. Like links in a chain. It was a simple yet elegant formula. Chemists now had a device for clearly illustrating the chemical structures of the molecules they were studying. There was just one problem. Benzene was the only known chemical that would not fit Kekule's formula. Benzene's chain of Carbon and Hydrogen atoms required more combining power than the formula would allow. "And all these organic chemistry professors are puzzling about it and offering different explanations. And one of them; August Kekule sitting by the fire one evening falls asleep and starts to dream about a snake. And if you think about a snake, what Kekule dreams of is the snake catches it's own tail. And if you think about this, maybe the thing is a ring and that gives you an answer to the puzzle. "The six Carbon atoms of the Benzene molecule weren't linked in a chain. Like the snake, they formed a ring. Each with a Hydrogen atom attached, with alternating single and double bonds. Within a short time Kekule's insight was confirmed and its effect was revolutionary. Chemists knew that all organic substances contained one or more carbon atoms and their molecules. With Kelkule's discovery they now had the underlying formula to explain how carbon combined with other molecules to form a world of chemical compounds. The modern era of organic chemistry was born. Now with this thing being so simple, that is to say the snake bites its tail. Why is this considered a great discovery? --Here's a recipe for new drugs, new medicines, new understanding. If you go back in time in Dalton's day couple of hundred compounds. Soon it's a couple of thousand, soon it's 10,000. Astonishing. Soon it's a hundred thousand. Last year 15 million new compounds were registered, all built on this simple template. This is a work of genius. In 1869, a Russian chemistry professor named Dmitri Mendeleev was writing a text book for his students, when he began to wonder how we could best explain to them the 63 elements that were known at the time. To help formulate his thoughts he constructed a card for each element. On each card he wrote the name of the element, its atomic weight, it's typical properties, and its similarities to other elements. He then laid the cards out like a game of solitaire and began arranging them over and over, searching for patterns. Then came the moment of discovery. Before him was something extraordinary. The elements fell into 7 vertical groupings. Each periodic grouping had members that resembled one another, both chemically and physically. Mendeleev had discovered the periodic table of the elements, a map showing how all of the elements related to one another. A map so precise that Mendeleev believed he could also use it to predict the existence and properties of three elements no one had yet discovered. One would be like Boron he said. One like Aluminum, and one like Silicon. Eventually the elements were discovered and Mendeleev was proven right. There was actually a little bit of controversy because a German chemist and Lothar Meyer had come up with roughly the same idea but Meyer didn't quite have as much courage. So that's actually an interesting thing. Here's this German who comes up with the same idea of periodicity of which there were hints already before, but he doesn't make the predictions that Mendeleev does. So here we see the power of a risky prediction in having people except a theory. There is nothing more powerful than making a prediction that's not obvious. --And then have it come true." And have it come true. The periodic table is our icon. I mean that it's what we associate with chemistry. You go into any chemistry room and you see it. Why is the periodic table of elements significant? it forever changed the way that everyone would learn and understand the elements. The periodic table of elements is to chemistry as notes of music are to a Beethoven sonata. In honor of Mendeleev, his name is now literally attached to the periodic table. The element 101 was named after him. It's called Mendelevium. It's not only chemists who like the periodic table, I hear you carry one around. --I do carry one, yes sir. --Show me! --You never know. And I seem to use it a lot." --Let's see. --It's a small one. --So I'm going to give you a test. Um what is under Nitrogen on the periodic table? --Nitrogen is 7. --Yes. --Well I have to think a second. "Sulfur." --No you're wrong. Close, you're one off. --That's why I carry it. --It's Phosphorus. --Oh Phosphorous, Phosphorus. 15. --Phosphorus is 15? -- Yeah, you have to add 8 at that point. See that's why I carry it. I can't remember. So it's seven plus 8. 15, Phosphorus. Okay. There's there's a pattern there. I get it now. At the turn of the 19th century, electricity was all the rage. people were busy making batteries and connecting them to just about anything to see the reaction. Electricity was like a new kind of fire. One of the great battery junkies of the day was Humphry Davy, the self taught English chemist. In 1807 Davey was performing a battery experiment in his lab. He melted some potash; a mineral found in the ground, that also forms in the ashes of wood. Chemists had speculated that potash was a compound of several elements, but had not been able to prove it. Davy wanted to see if electricity might provide the answer. He ran some wires from one of his biggest batteries to the melted potash. Pure Potassium began to emerge. Davy had discovered the power of electricity to react with chemicals and transform them. Eventually electrochemistry led to the rise of the aluminum industry, the production of semiconductors, solar panels, LED displays, even rechargeable lithium batteries. In the 1850s Robert Bunsen and his research collaborator Gustav Kirchhoff conducted a series of experiments to determine why substances emitted specific colors when placed in a flame. The color they determined, indicates what elements are present in the substance. For example, if Sodium is placed in a flame, they observe shades of yellow. Copper, shades of green. Strontium, shades of red. That was a good one. While watching the experiments Kirchoff was reminded of how a prism spreads light into a rainbow of colors. So, using a prism and the pieces of a small telescope Bunsen and Kirchoff built the first spectroscope, an analytical device they hoped would help them see the spectra coming from heated substances. And it worked. As an element was put into the flame of a bunsen burner, the light from the heated substance passed through the prism of the spectroscope where it then spread into a ribbon-like spectrum of colors, riddled with dark lines. The combinations of bright colors and dark lines were like barcodes, indicating what atoms were present. When burned, each element produced a completely unique spectrum. Using their spectroscope, Bunsen and Kirchoff were able to discover two new elements; Cesium and Rubidium. One day Bunsen and Kirchoff decided to test their invention with sunlight. It produced a spectrum that featured two lines that were identical to those in the spectrum produced by sodium. Bunsen and Kirchoff had discovered the presence of sodium in the sun 93 million miles away. Suddenly scientists had a tool to help them study the chemistry of the heavens. [Lift off. We have lift off.] Today the legacy of this great discovery lives on in the exploration of space. A form of spectroscopy is being used to study the atmospheres of planets, to search for signs of water. Signs of life. Our next great discovery is the story of Joseph Thomson and the electron. ["Here we are."] --So everything that we can see is made of chemicals. --That's right --What's the future?" --And they're all bonded through electron interactions. --Thank goodness. "To find out about it I paid a visit to Harvard University. Dudley Herschbach is a professor here and winner of the 1986 Nobel Prize in Chemistry... for his research into the dynamics of chemical elementary processes. --So Thomson discovered the electron. --Well it is of course said that way, but he didn't discover it in the sense that he said, "Eureka! I've got this thing. Here it is." He did an experiment that allowed him to measure the ratio of the charge, the electric charge, the mass and then later is able to get a rough measurement of the charge and therefore show the mass was very very small. It was about one two-thousandth's of the mass of the lightest known atom. The Hydrogen atom. So it showed that he could extract an experiment, a very small piece of an atom. Well that was a tremendous shock. --Pun intended. --Yes, yes...electrical piece from an atom. It was a very small part of the atom.