Beyond the Elements: Reactions
From explosions to photosynthesis, chemical reactions transform our world.
Just about every solid, liquid, or gas in the world as we know it begins with reactions between individual atoms and molecules. Host David Pogue dives into the transformative world of chemical reactions, from the complex formula that produces cement to the single reaction that’s allowed farmers to feed a global population by the billions—a reaction that when reversed, unleashes the powerful chemistry of high explosives. (Enjoy this program with Audio Description.)
Beyond the Elements: Reactions
PBS Airdate: February 3, 2021
DAVID POGUE (Science and Technology Author): What’s it take to make our modern world?
Ah!
Dah!
That’s amazing!
I’m David Pogue. Join me on a high-speed chase through the elements and beyond.
Oh, my god.
As we smash our way into the materials, molecules and reactions…
AMANDA CAVANAGH (University Of Illinois, Realizing Increased Photosynthetic Efficiency [RIPE)]): It’s a really cool enzyme, because it makes life on Earth possible.
DAVID POGUE: …that make the places we live, the bodies we live in and the stuff we can’t seem to live without.
The only thing between me and certain death is chemistry? From killer snails…
MANDË HOLFORD (Hunter College): Just when you think you’ve heard of everything, nature will surprise you.
DAVID POGUE: …and exploding glass to the price a pepper-eating Pogue pays…
There’s got to be some easier way to learn about molecules.
…we’ll dig into the surprising way different elements combine together and blow apart.
Come for the chemistry, but stay for the bacon blowtorch.
The power of bacon!
Beyond the Elements: Reactions, right now, on NOVA.
Imagine that you’re about to take your first shot in a game of pool, the “break.” But when the cue ball hits the other balls they all turn into a rat. Or imagine you snap a pencil in two, and it becomes a flower and a fork.
That’s how weird and surprising some chemical reactions are. You can take something as dangerous as the element sodium, which explodes on contact with water, combine it with a lethal gas, the element chlorine, and end up with something utterly different: sodium chloride, table salt, for your fries.
Transformative chemical reactions are everywhere. They’re going on all the time. They put the bang in explosives…
That’s a reaction!
PEPPER-EATING CONTEST ANNOUNCER (Berks Pepper Jam): Round 2.
DAVID POGUE: …and the “heat” in hot peppers.
What am I doing?
Learning how to harness them has given us some control over our world and maybe even helped to make us human.
And few folks know more about chemical reactions…
THEODORE GRAY (Author): This is not normal fire.
DAVID POGUE: …than my old friend Theo Gray. Today, I’ve come to his mad scientist lair, in Illinois, to find out more about one of the most powerful weapons in our reaction arsenal...
Oh, ho, ho, ho!
…fire.
THEO GRAY: Fire is a chemical reaction, plain and simple. It happens to be the most important chemical reaction ever, times 10, bar none. When you think about the importance of fire to human beings becoming who we are, it’s kind of the start of civilization, almost, discovering how to control this amazing thing. It feeds us, chases away the bears, it lights up the night. There’s almost nothing you could name that’s more important than fire.
DAVID POGUE: So, what is fire, anyway? You may have learned this in school. To make fire, a kind of combustion, you need fuel, plus heat, plus oxygen. That formula is simple, but what’s happening isn’t.
THEO GRAY: And what’s actually happening here is kind of subtle. The wood itself isn’t really burning. You see the flames?
DAVID POGUE: Yeah.
THEO GRAY: Most of the reaction is happening up in the air, above the wood, because it needs to mix with air. Like, there’s no air in the wood. And what’s happening is the heat of the flames, here, are breaking down and evaporating compounds in the wood, bringing them up into the air.
DAVID POGUE: Those gases from the wood are complex molecules, made mostly of hydrogen, carbon and oxygen. When the rising gases enter the high temperature area of the flames, they’re joined by oxygen from the air in a swirling cauldron of complicated reactions.
The gases break down and their atoms rearrange. If the gases burn completely, they’ll form water and carbon dioxide. More often, incomplete burning produces a variety of other molecules.
Importantly, for us, the reactions also release energy, the light you see and the heat you feel. And that, at its heart, is what happens in chemical reactions, the breaking and making of bonds and the shuffling around of atoms.
THEO GRAY: You take two different things, you smash them together, they rearrange themselves, and then you get…something else comes out.
DAVID POGUE: And one of the big-time players in the game is oxygen.
THEO GRAY: You ready?
DAVID POGUE: With enough heat, it reacts with just about anything, as Theo soon shows me in his barn.
This powerful cutting tool is called a “thermic lance.” It uses pressurized oxygen fed through a metal rod. This one’s made of iron.
We don’t normally think of iron as something that can burn, but when lit in the flow of oxygen, it does, generating so much heat…
Wow!
…that you can cut through a brick or concrete.
Demolition crews use large thermic lances to slice up all sorts of big unwieldy things, from bridges, to ships, to machinery. But does the rod that burns in the stream of oxygen need to be metal?
I shudder to ask why you’ve got plates of bacon here.
THEO GRAY: Well, because bacon is the funniest thing that you can form into a tube and shoot oxygen through. Unfortunately, actual American-style bacon doesn’t hold together well enough. We need the engineering grade. This is Italian prosciutto.
DAVID POGUE: Theo has already baked some tubes of prosciutto. The next step is to wrap them in yet another piece, to create one large hollow tube, which he hooks up to his oxygen tank.
THEO GRAY: Okay, so now, what can we do with this? The same thing you do with any sort of thermic lance. You cut something with it. Uh, we’re going to cut steel because, why not?
DAVID POGUE: No. You’re going to cut steel with bacon?
THEO GRAY: Yes, a steel baking pan.
DAVID POGUE: Wow.
THEO GRAY: You just have to get it hot enough.
DAVID POGUE: The power of bacon! That’s amazing!
THEO GRAY: Yeah. I mean, that’s a good amount of cutting there.
DAVID POGUE: I’ve heard of steel-cut oatmeal for breakfast, but…
THEO GRAY: Bacon-cut steel?
DAVID POGUE: Gaining control over fire has had an immeasurable impact on human civilization. In fact, the most popular construction material in the world has its roots in one of the oldest pyro technologies: roasting a certain kind of rock.
We know it as concrete. Modern concrete is a mixture of aggregate materials like sand, gravel and crushed stone with a binder, these days, most often, cement. And that’s key, because people are always confusing concrete and cement.
Cement is the glue, concrete is the end product. Cement sidewalks? No! That’s concrete. Cement trucks? Uh-uh. They carry concrete. But cement is the key ingredient, and that’s why I head to the LafargeHolcim cement plant, the largest in the U.S., located outside St. Louis, Missouri.
JOHN GOETZ (LafargeHolcim): We shoot rock every day.
DAVID POGUE: My day with plant manager, John Goetz begins with a bang.
VOICE OVER RADIO: Fire in the hole!
DAVID POGUE: Is it safe to go down there?
JOHN GOETZ: Not quite.
How’s that for you?
DAVID POGUE: That’s a reaction.
JOHN GOETZ: That’s awesome, huh?
DAVID POGUE: Do it again.
Now that, my friends, is a lot of limestone.
JOHN GOETZ: That’s a lot of rock.
DAVID POGUE: Before long, this will be holding together America’s buildings and sidewalks and…
JOHN GOETZ: That’s right, we’re going to turn this limestone into cement.
DAVID POGUE: But what exactly is limestone?
It’s mostly calcium carbonate, a compound that, as its name says, has two parts. There’s a calcium atom that has given up two of its electrons, making it a positively charged ion. The other part is carbonate, made up of three oxygen atoms that are sharing electrons with a carbon atom. Sharing electrons is called “covalent bonding.” The two electrons from the calcium have joined the party, making the carbonate a negative ion. The positive calcium ion and the negative carbonate ion attract, forming—surprise—an ionic bond.
From the quarry, the limestone rock gets gradually crushed down, along with some clay and other ingredients, into a fine powder called “raw meal,” in preparation to enter the centerpiece of this whole operation: a rotary kiln, about 22 feet in diameter and about 100 yards long.
JOHN GOETZ: It’s a big kiln, largest in the world.
DAVID POGUE: Kiln, as in an oven?
JOHN GOETZ: Correct. The gas temperature inside the kiln right here is about 2,000 degrees Fahrenheit.
DAVID POGUE: Just before it enters the kiln, the powdery raw meal is dropped down through the kiln’s hot exhaust gases. By the time it reaches the bottom and the entrance to the kiln, the heat has transformed the calcium carbonate from the limestone into carbon dioxide gas and calcium oxide, also known as quicklime.
Normally the kiln rotates at a speed of about four times a minute. And ordinarily this whole thing would be turning, but it was shut down for maintenance…
Oh, man, the mouth of the dragon!
…giving us a chance to see it from the inside.
So the whole thing is turning.
JOHN GOETZ: The whole thing is turning over, four revolutions a minute. As the material comes down the kiln, there’s a burner pipe with a flame, right here, inside the kiln and heating the material to 2,600 degrees, and the flame temperature is about 3,000 degrees Fahrenheit.
DAVID POGUE: At this point it looks like dark baby powder?
JOHN GOETZ: At this point it looks like lava.
DAVID POGUE: Oh, it does?
JOHN GOETZ: Yes, it’s red hot lava.
DAVID POGUE: As the main ingredient, calcium oxide journeys down the kiln, getting hotter and hotter, it reacts with the other ingredients in the raw meal, creating complex synthetic compounds. By the time the whole mix reaches the end, it has a new name.
JOHN GOETZ: “Clinker.”
DAVID POGUE: This stuff is called clinker?
JOHN GOETZ: It’s clinker.
DAVID POGUE: You couldn’t call it something dignified…
JOHN GOETZ: Oh, I didn’t name it.
DAVID POGUE: …like “calcium carbonate” or “sulfur trioxide?” Clinker?
JOHN GOETZ: Clinker coming out of the kiln process, before it goes into the cooler.
DAVID POGUE: And clinker just refers to that limestone brew that’s been cooked.
JOHN GOETZ: Correct.
DAVID POGUE: But it still isn’t cement. In the final stage, they add a little more limestone and hydrated calcium sulfate, a common mineral known as “gypsum.”
Conveyer belts seem to really be a thing around here.
And the whole thing gets ground back down to a fine powder.
And here it is, at last; no more grinding, no more ingredients. This is the finished product?
JOHN GOETZ: This is cement.
DAVID POGUE: This is cement, from the virgin limestone bluffs of Missouri.
JOHN GOETZ: There it is.
DAVID POGUE: This LafargeHolcim plant produces up to about 4.4-million tons of cement a year. But that’s just a small percentage of the 97-million tons produced in the U.S. and the 4.5-billion tons produced internationally.
Virtually all of it ends up in concrete, that mixture of cement, water and rock that is second only to water as the most consumed resource on the planet.
That comes at a price though: a massive carbon footprint. In 2016, cement production emitted about eight percent of the global total of greenhouse gases, over half of that from the production of clinker.
Proposed solutions to this problem range from using wood to build high rises, like this 18-story one in Norway; to injecting CO2 back into concrete as it cures, like this company in New Jersey, making pavers; and even growing cement using bacteria, though scaling up those ideas remains a challenge.
Maybe the solution, or part of the solution, to greenhouse gas emissions and global warming will come from a breakthrough in chemistry. That may sound foolishly optimistic, but the discovery of a chemical reaction over a hundred years ago changed the trajectory of humanity, though few know the story.
At the start of the 20th century, farmlands like these didn’t look so verdant. And with populations rising, scientists wondered whether, in the near future, there would be enough food. The problem was nitrogen. Animals need nitrogen to grow. So do plants. But before the 20th century, farmers mainly depended on compost and manure to supply it to their crops, essentially recycling nitrogen from dead plants and animals. But there was only so much nitrogen in that cycle.
Eventually, the growing population would exceed the farmlands’ capacity to grow food, leading to mass starvation. But there was a solution in the air, literally.
Our atmosphere is almost 80 percent nitrogen, but that doesn’t do plants any direct good. That’s because it’s in the form of N2, two nitrogen atoms sharing in a triple bond. Three electrons from each atom are fully shared between them, which, as Ed Cussler, a chemical engineer and professor emeritus at the University of Minnesota explains, makes the nitrogen molecule one tough cookie.
So, the atmosphere is 78 percent nitrogen, why can’t the plants just take the nitrogen out of the air?
ED CUSSLER (University of Minnesota): Because you can’t break this little bastard in half.
If you take the nitrogen, you have to break this bond, this triple bond, between the two nitrogen atoms. It’s almost the hardest bond, the most difficult bond that we know. Basically, it’s almost inert.
DAVID POGUE: So, the scientific challenge was for someone to find a way to take that stubborn nitrogen molecule from the air, and bust it apart, to create something plants could use, to invent a synthetic fertilizer.
Around 1910, German chemist Fritz Haber and his team found the answer, which they demonstrated using this tabletop machine. From nitrogen gas and hydrogen gas, he could produce NH3, ammonia, a fertilizer itself and a starting point to produce others.
German chemist Carl Bosch brought Haber’s work to an industrial scale, which is why it is known as the “Haber-Bosch” process.
Ed and his colleague, Joe Franek, show me their tabletop version.
DAVID POGUE: Joe, maybe you can show us, a little more hands on, how the Haber-Bosch process works?
JOSEPH FRANEK (University of Minnesota): All right. We’re going to put a quantity of nitrogen in this syringe; then we’re going to put three times that amount of hydrogen in this syringe. We’re going to light our Bunsen burner, and we’re going to pass that mixture of gasses over what will be our hot catalyst, which is iron, in this case, and that will facilitate the conversion of the nitrogen and hydrogen into ammonia.
DAVID POGUE: Okay, so one syringe full of nitrogen and three times as much hydrogen, because the formula for ammonia is NH3?
JOE FRANEK: There you go.
DAVID POGUE: It all makes sense.
Joe passes the mixture over some steel wool heated by a Bunsen burner. The steel wool acts as a catalyst, a material that helps a reaction along while not getting consumed by it.
After six minutes, it’s time to see if it worked.
JOE FRANEK: So, we now have all of our gases, our unreacted nitrogen and hydrogen and the ammonia we produced, in this one syringe. And what I’m going to do is flush all of these gases through our indicator tube.
If we flush some ammonia through these yellow beads, they’ll turn blue.
ED CUSSLER: Bravo.
DAVID POGUE: I see blue.
So, how much ammonia do you think we got?
JOE FRANEK: Well, our indicator on the tube says that we have just slightly less than two parts per million of ammonia.
DAVID POGUE: Two parts per million? So out of every million molecules, we got two of ammonia? At room temperature, this process barely works and even with our burner heating things up a bit, nitrogen gas is so inert, the reaction isn’t much better.
Part of the problem is that this equation is a two way street. Some reactions are one way, “irreversible.” When you bake a cake, you can’t unbake it. But the Haber-Bosch process, like many reactions, goes both ways at the same time. So, while some of the nitrogen and hydrogen are forming ammonia, some of the ammonia is breaking down, into nitrogen and hydrogen.
The trick is to find the optimal conditions where that balance heads in the direction you want.
One tool is pressure. Bosch’s industrialized version compressed the gases to around 175-times normal atmospheric pressure. And that huge pressure cooker ran very hot, 550 degrees Celsius, around 1,000 degrees Fahrenheit, enough to make the hydrogen and nitrogen react with the catalyst, but not so hot as to break up a lot of ammonia.
Though the process requires extreme conditions, the discovery of a way to split apart that stubborn nitrogen molecule changed the world. It opened the door to the creation of artificial fertilizers.
And it’s hard to overstate the impact of the Haber-Bosch process on our ability to feed humanity.
What were the lasting effects of this introduction?
ED CUSSLER: Two-billion more people. If you lose this chemical fertilizer, you lose two-billion people. They starve. This is not a hypothetical issue. Haber-Bosch is the chemistry that you wish for, because it’s the chemistry that improves the amount of food that you can grow on our planet. And that makes an enormous difference to the stability, the health, the wellbeing of the people on the planet.
DAVID POGUE: So, one chemical reaction wound up radically changing humanity.
ED CUSSLER: Yeah, some people argue it’s the most important single chemical reaction.
DAVID POGUE: Wow.
But before you go out and hug your nearest ammonia-producing chemical plant, you may want to consider the downsides. Now that fertilizer is abundant, growers often apply too much. Runoff fertilizer has led to giant algae blooms and dead zones in oceans. Also, making ammonia uses a lot of fossil fuel. Annually, the industry as a whole accounts for one percent of global CO2emissions.
Ed Cussler is part of a team of scientists, at the University of Minnesota, working on a greener approach to producing ammonia. This is the industrial Haber-Bosch process, in a smaller package.
ERIC BUCHANAN (University of Minnesota): This ammonia reactor, here, is making about 25 tons of ammonia a year. A standard commercial ammonia plant is making thousands of tons a day.
DAVID POGUE: Oh.
ERIC BUCHANAN: So, this is a much smaller scale.
DAVID POGUE: It still depends on high temperature and pressure, but it’s powered by nearby wind turbines. You’re taking nitrogen out of the air, you’re making hydrogen out of the water, you’re making it out of nature.
CORY MARQUART (University of Minnesota): Yup. Right here in this room. The long-term vision is that small facilities like this pilot plant could make enough “green” ammonia for a county’s worth of farms: in this area, about 130,000 acres.
ED CUSSLER: We are making fertilizer from air and water, it’s just straight alchemy. You’re not going to get rich doing it in the new green way, but you can sure make a difference in the way the planet is.
DAVID POGUE: Scientists estimate that 50 percent of the nitrogen atoms in any person alive today, at one point passed through the Haber-Bosch process. Yet, Fritz Haber’s legacy is mixed. He won the Nobel Prize in Chemistry for his discovery but is also considered the “Father of Chemical Warfare,” having proposed and supervised its use in World War I by the German army.
Some historians believe the Haber-Bosch process itself may have extended that war by years, because it gave Germany a new source of nitrogen compounds, key ingredients in explosives.
What makes them “key?” It all goes back to that stubborn nitrogen molecule. Think of it like a spring. Pulling the atoms apart takes a lot of energy, and sticking them into nitrogen compounds keeps them separated. But in explosives, those compounds are designed to fall apart quickly, freeing the nitrogen atoms to spring back together and releasing the stored energy from pulling them apart.
It seems like a good place to blow stuff up without risking hitting anything.
TOM PLEVA (Energetic Materials Research and Testing Center, New Mexico Tech): Yeah, that’s why we like having our surrounding mountains.
DAVID POGUE: To better understand the role of nitrogen compounds in explosives I’ve decided to return to see some old friends, the engineers and scientists at the Energetic Materials Research and Testing Center at New Mexico Tech. We’ve had some fun in the past.
JONATHAN MYRKLE (Energetic Materials Research and Testing Center, New Mexico Tech): Well, this is the most fun tailgate you’ll ever come to.
DAVID POGUE: So, let’s see what ordnance tech Jonathan Myrkle and chemist Tom Pleva have in store for me today.
It’s cotton, cotton balls?
TOM PLEVA: That’s correct.
DAVID POGUE: Like, cotton balls?
TOM PLEVA: Yep.
DAVID POGUE: Now you might think that cotton balls don’t explode, and you’d be right.
JONATHAN MYRKLE: That was underwhelming.
DAVID POGUE: Cotton fiber is about 90 percent cellulose, a key structural component in green plants composed of carbon, hydrogen and oxygen but no nitrogen. So, our cotton balls will burn, eventually, though not explode.
The spores are erupting.
But back in the mid-1800s, chemists discovered that they could add, to cellulose, what are called “nitro groups,” each a nitrogen and two oxygen atoms. That turned it into nitrocellulose, also called “guncotton.”
Those nitro groups made something that burns like this, into something that burns like this: flash paper. But nitrocellulose is no joke. In a confined space like a gun barrel, it can be powerful. It was the propellant the military used to launch the shells out of these 16-inch guns on Iowa-class battleships, and it’s still a propellant today, in 155 millimeter artillery.
Our next test…
JONATHAN MYRKLE: Okay.
DAVID POGUE: …is 50 pounds of nitrocellulose propellant, the kind used in those large-bore guns.
We give you 50 pounds of guncotton. Since the sphere container isn’t sealed, it won’t explode.
But what will happen? After Jonathan wires it up, we head to a nearby bunker to find out.
JONATHAN MYRKLE: Here we go. Three, two, one…
DAVID POGUE: Compared to plain cotton, this is a show. The burning nitrocellulose generates rapidly expanding gases, including carbon dioxide, carbon monoxide, water vapor and, of course, nitrogen.
It’s pretty.
Packed behind a shell in the barrel of a gun, the pressure from the expanding gases would hurl the shell forward. In our open bowl, it’s more like fireworks, with the gases sending burning pellets up in the air.
TOM PLEVA: That’s just a propellant. That’s a low grade here. We’re going to move on to actual explosives, now.
DAVID POGUE: Oh, yeah? What’s first up?
TOM PLEVA: So, we’re going to start off with ANFO.
DAVID POGUE: ANFO?
TOM PLEVA: That is the biggest mining explosive that we have.
DAVID POGUE: Oh, cool!
ANFO is an industrial explosive used in mining and construction. It accounts for about 80 percent of all the explosives used in North America.
Probably no chemical shows better the intimate relationship between fertilizer and explosives. Though the name ANFO stands for Ammonium Nitrate and Fuel Oil, it’s over 90 percent ammonium nitrate, the same stuff as synthetic fertilizer.
Ammonium nitrate is built around nitrogen atoms, so it packs way more nitrogen than nitrocellulose. That means ammonium nitrate can be very dangerous.
This is the aftermath of the deadliest industrial accident in U.S. history: the explosion of over 2,000 tons of ammonium nitrate aboard a ship, in Texas City, Texas, in 1947.
In 2020, in Beirut, Lebanon, there was similar explosion. A waterfront warehouse containing thousands of tons of ammonium nitrate caught fire and detonated. The blast killed over 200 people, injured thousands, and left an estimated 300,000 homeless.
Our ANFO test will be just 50 pounds of the stuff.
JONATHAN MYRKLE: Fifty pounds.
DAVID POGUE: To get a reaction going, even one that will release a lot of bang…
Wow!
…you need to put some energy into it first, to get some of the bonds to break. That’s called “activation energy.”
This is nitrogen triiodide, an explosive whose existence is so precarious, minimal activation energy is needed, even just the touch of a feather.
In contrast, ANFO is hard to set off. So, Jonathan hooks up a booster, a smaller explosive.
Since much of EMRTC’s research and training involves explosions in human-occupied environments, they typically add a wooden dummy for scale and to demonstrate an explosive’s effect.
JONATHAN MYRKLE: You good? Okay, here we go. Three, two, one…
DAVID POGUE: Oh, ho! That, my friend, is a firecracker. That was like seven stories. So what just happened?
Jonathan ignites the booster.
That’s the black smoke you see. The pressure wave from the exploding booster, in turn, detonates the ANFO, breaking the bonds holding the ANFO atoms together. They rearrange into more stable gases: nitrogen, carbon dioxide and water vapor, along with some carbon monoxide and nitrogen oxides. The hot gases rapidly expand, creating a supersonic shockwave traveling at about two miles per second.
If you look at just the nitrogen atoms of the ANFO, it’s like the “un-Haber” process. Most of the nitrogens from the ammonium ions and nitrate ions reunite into their more stable preferred state, N2. In fact, about half of the power of the ANFO explosion comes from nitrogen atoms reforming into nitrogen molecules.
Here we are, what, a quarter of a mile away? And you could feel the ground shaking.
TOM PLEVA: Yup.
DAVID POGUE: And that’s 50 pounds.
TOM PLEVA: That’s only 50 pounds, yes.
DAVID POGUE: Next up, you’ve seen it in movies and you probably even know its name.
ACTOR 1 FROM RUSH HOUR: What’s that?
ACTOR 2 FROM RUSH HOUR: That’s C-4.
DAVID POGUE: And just one look at its active ingredient should tell you we’ve upped our game: Cyclotrimethylenetrinitramine, commonly known as R.D.X.
While it has three nitro groups, there’s even more nitrogen built into its ring. And even though the nitrogen triple bond is one of the strongest in nature, the single bonds between the nitrogen in the ring and the nitro groups are rather weak, often the first to fail when detonated.
Oh, my! The last one for the day for us.
JONATHAN MYRKLE: Ah, yeah. Fifty pounds of C-4.
DAVID POGUE: All right. Should I be offended that they’ve dressed him like me? Is there a hidden message in that?
JONATHAN MYRKLE: I wouldn’t take it personally, but you know.
DAVID POGUE: All right.
JONATHAN MYRKLE: Oh, wait, I’ve got to go do that.
DAVID POGUE: Oh, but it looked so cool.
JONATHAN MYRKLE: I know, I know.
Charging. Okay, here we go. Three, two, one…
DAVID POGUE: Oh, my god!
When the detonation pressure wave hits the R.D.X. molecule, the ring compresses and then flies apart. The atoms recombine into carbon monoxide, water vapor and nitrogen gas. Those reactions produce far more heat than ANFO does, which makes the gases expand much more rapidly, giving R.D.X. over twice the explosive power.
TOM PLEVA: So, we have more heat and energy in there.
DAVID POGUE: And there’s more nitrogen in there.
TOM PLEVA: Exactly.
DAVID POGUE: Does that mean that the future is just all nitrogen?
TOM PLEVA: That is the goal. We are trying to make entirely nitrogen-composed explosive molecules.
DAVID POGUE: Here’s one from the drawing boards with a great name: octaazacubane. Entirely made of nitrogen, it is predicted to have a faster velocity of detonation than any known non-nuclear explosive, if someone can just figure out how to make it.
I think that’s all that’s left.
And so ends our day of the un-Haber-Bosch process.
Much of the nitrogen in our explosives has returned to its happy, or at least extremely inert state, as N2 molecules, in the atmosphere, over New Mexico.
In chemistry, reactions tend to consume other ingredients, transforming them into something new. That’s the process that chemical equations are designed to explain. But in biology, molecules can sometimes bind to each other without consuming or producing anything new. They can act astriggers or messengers, or, as it’s sometimes described, like a key fitting into a lock.
To learn more about molecular locks and keys, I’ve come to experience them viscerally…
Mmmm. Oh, wow.
…Here, at the Berks Pepper Jam, in Bethel, Pennsylvania…
VENDOR: Smell that! Mmmm.
DAVID POGUE: …an annual festival of food, entertainment…
ANNOUNCER: Eat, eat, eat!
DAVID POGUE: …and contests, all centered on chili peppers.
“Reaper Evil Hot Sauce.” They do have an ambulance on hand, right?
VENDOR: They do.
DAVID POGUE: When it comes to peppers, I’m a novice. But the first thing you need to know is that the black pepper you see sitting with salt and chili peppers have different chemistries and histories. Black pepper is the dried ground-up fruit of a flowering vine native to Asia. Its kick comes mainly from the molecule piperine.
While one side of the world had black pepper, the other side had chili peppers, first domesticated by Mesoamericans, and then traded around the world by European explorers. The main active ingredient in chili peppers is the molecule capsaicin. More on that in a bit.
EMCEE: Three, two, one, eat!
DAVID POGUE: The Jam features a pepper-eating contest for kids, but they wouldn’t let me in. So, I plan on entering the one for adults, after I get some advice.
I’ve actually never eaten a pepper by itself.
VENDOR: Bow out when you feel you should.
DAVID POGUE: Really?
VENDOR: A raw pepper is a completely different deal.
VENDOR: I can’t do it.
DAVID POGUE: You can’t eat a reaper? Is there any way I can prepare?
ATTENDEE: You got your will made out?
VENDOR: You don’t have anything to do for the next three days, do you? You’re going to feel great Monday morning.
EMCEE: A round of applause for Lizzie. Well done! Woo hoo!
DAVID POGUE: Time to put my tongue to the test.
ANNOUNCER: Long hots, red Fresno…
DAVID POGUE: Here’s how the contest works. There are ten rounds of increasingly hot peppers…
ANNOUNCER: …Peach Copenhagen, Big Red Mama…
DAVID POGUE: …their spiciness measured on a scale invented, in 1912, by pharmacist Wilbur Scoville. It estimates the amount of capsaicin in each pepper. Contestants have to eat a pepper and then wait two-and-a-half minutes to allow the burn to grow. If they drink the milk in front of them, a popular way to douse a tongue on fire…
EMCEE: They are eliminated.
DAVID POGUE: …they’re out.
My competitors include some rugged looking characters, and Leah…
LEAH (Pepper-eating Contest Participant): I’ve never done this before. I figured this out two hours ago.
DAVID POGUE: …a 15-year-old who entered with the permission of her parents.
Woo hoo, bring it on!
ANNOUNCER: We begin with the long hots. Let’s turn up the heat! Eat!
DAVID POGUE: And we’re off! Zesty, with just a hint of poison.
ANNOUNCER: Round 2. We’re going to start with the red Fresno pepper.
Eat! Eat! Eat! Eat! Eat! Eat!
DAVID POGUE: There’s got to be some easier way to learn about molecules.
ANNOUNCER: All right, are we ready? Eeeeaaaat!
DAVID POGUE: That was not designed for human consumption.
ANNOUNCER: Round number 4, habanero peppers.
Eat, eat, eat, eat, eat.
DAVID POGUE: Parts of my body I didn’t know I had are on fire.
ANNOUNCER: Ten more seconds. You got this.
DAVID POGUE: I can’t. I can’t.
ANNOUNCER: No! Don’t do it! No!
The Orange Copenhagen pepper. Eat!
DAVID POGUE: What am I doing? Oh, man. Oh, my god.
I want it! Wherever you are, Scoville, I hope you rot!
Cheers!
ANNOUNCER: Oh, no!
DAVID POGUE: So, I’m the first to fall.
Thank you. Is there a porta potty?
But there’s a bigger mystery. How does a pepper’s capsaicin convince my mouth it’s on fire?
Not recommended.
I think I’ll find the answer here at Penn State University’s Department of Food Science.
JOHN HAYES (Sensory Evaluation Center, The Pennsylvania State University): We all study food, so, you’ve got psychologists and microbiologists.
DAVID POGUE: I’m here to see John Hayes. He knows a thing or two about the active ingredient in these.
JOHN HAYES: So, when you went and tasted them, what did you experience?
DAVID POGUE: Oh, man. My gut twisted, my tongue burned, my flesh burned. I cried, I got red, my nose ran.
It’s like putting your tongue on the stove and leaving it there.
JOHN HAYES: That was an “aversive” response. This plant has evolved a chemical called capsaicin. And the reason it makes that is to keep animals from eating the chili pepper.
DAVID POGUE: Oh, man, the chili festival people never got that message. And we’re just a really stupid species?
JOHN HAYES: Exactly. We’re one of the only species that learned to like that sensation.
DAVID POGUE: Ultimately, pepper plants are playing a pretty good trick on humans, as well. Capsaicin really is a “key” ingredient. It has a long spindly tail, attached to a ring.
JOHN HAYES: That ring end fits into a specific receptor that’s expressed all over your body.
DAVID POGUE: Not just our tongue?
JOHN HAYES: Not just your tongue.
DAVID POGUE: Oh, man.
JOHN HAYES: This receptor, this lock, is actually a heat pain sensor.
DAVID POGUE: Normally, the receptor, called T.R.P.V.1, activates when it comes in contact with something over 106 degrees. The result is a pain message to the brain: “Ouch! Something’s hot.”
JOHN HAYES: It’s a warning signal, to tell your body “danger.”
DAVID POGUE: And here’s the tricky part. When you eat peppers, those capsaicin keys fit into the heat pain receptors in your mouth, altering their sensitivity.
JOHN HAYES: And so, what the capsaicin does is it fits into this molecular thermometer, and it lowers the temperature at which it activates it.
DAVID POGUE: Like a changed thermostat, they now activate at body temperature, sending a false signal that’s identical to the one your brain would receive if you ate something literally burning hot.
It lowers the temperature at which we feel burning pain?
JOHN HAYES: Yes.
DAVID POGUE: But it’s not actually burning us?
JOHN HAYES: Correct.
DAVID POGUE: I’m not going to see scar tissue?
JOHN HAYES: No.
DAVID POGUE: No matter how hot it is, it’s all a fake-out?
JOHN HAYES: Absolutely.
EMCEE: Up next, the Yellow Seven Pot pepper.
DAVID POGUE: Back in Bethel, the pepper-eating contest is entering its final rounds.
ANNOUNCER: Eat!
CONTESTANT: That was warm.
CONTESTANT: Oh, it’s burning now.
CONTESTANT: I’m trying to think of a happy place. I can’t find one.
DAVID POGUE: Evidence that capsaicin’s working on the molecular locks of everyone’s heat pain sensors is easy to see, as they eat a Big Red Mama, rated at over a million Scoville heat units.
ANNOUNCER: Don’t tap out now! Don’t tap out!
DAVID POGUE: One more falls. We are down to the final four.
ANNOUNCER: I’m ready to leave. I can’t abuse these people anymore.
DAVID POGUE: This time, the organizer adds concentrated pepper extract. How long can this go on? Then, suddenly, a resolution that no one saw coming.
ANNOUNCER: Oooh! Leah beat them! Big round of applause. Big round of applause. Big round of applause.
DAVID POGUE: Leah, I am not worthy. You rock! What does a woman with that fortitude and strength want to be when she grows up?
LEAH: A fighter pilot.
DAVID POGUE: Why am I not surprised?
Ultimately, the Capsaicin molecule is an illusionist, able to trick my nervous system into thinking my mouth is on fire.
But what about the molecules that pose real danger, molecules designed by nature to kill?
Time to meet my first Professor of Venoms, Mandë Holford, of Hunter College.
Now, I couldn’t help noticing, there’s a huge, terrifying tarantula on me. Is she poisonous?
MANDË HOLFORD: No, no, she’s not poisonous.
DAVID POGUE: Oh, whew!
MANDË HOLFORD: She is, however, venomous and could still be lethal.
DAVID POGUE: Thanks for bringing that up. Poisonous and venomous don’t mean the same thing?
MANDË HOLFORD: No, no, no, not at all.
DAVID POGUE: Poisonous versus venomous: it all comes down to the delivery system. If you bite it and get sick, it’s poisonous, but if it bites you and you get sick, it’s venomous. In general, the source of their toxins is different, as well.
This poison dart frog becomes poisonous from its diet. If raised in captivity, on different foods, it can become non-toxic, whereas this rattlesnake generates its own venom. It’s built into its D.N.A. So, snakes, scorpions, spiders: which fearsome creature is the focus of Mandë’s work?
Killer snails? Is it accurate to say that you study killer snails?
MANDË HOLFORD: Killer snails are actually my affectionate term for venomous marine snails. And so, these are snails that live in the sea, and they have a venom, like snakes or scorpions or spiders, and the venom can be very lethal to humans.
DAVID POGUE: It’s true that the snail can kill you, but usually it’s just looking for dinner, a worm or a fish.
So, I’m a fish. What happens to me?
MANDË HOLFORD: Well, what happens is this guy will smell that you’re in the water, right? He puts out something called a siphon, and it’s a chemosensory organ, smells that, “Hmm, tasty meal in the water,” then it sticks out something like a tongue. It’s called a “false” tongue, “proboscis.” And, on the tip of the tongue, it has a little tooth, filled with venom that then will get injected into the fish. The fish instantly will become paralyzed, depending on what cocktail of venom gets injected into it. The snail will then open its mouth really wide, swallow the fish whole and have a really nice, tasty meal.
DAVID POGUE: The whole thing sounds so improbable.
MANDË HOLFORD: I love it. Just when you think you’ve heard of everything, nature will surprise you with something new.
DAVID POGUE: So, what’s in that paralyzing venom? To find out, Mandë and her team collect specimens from around the world. Back at the lab, they analyze tissue samples from the snail’s muscular foot and its venom gland.
JULIETTE GORSON (Hunter College): So, we’re eventually going to look at the D.N.A., so we can make a species identification. That, we can use the foot tissue for. And then the venom gland tissue we can use to look for the individual venom toxins within the venom duct.
DAVID POGUE: Turns out, the cone snail’s venom isn’t one thing but a cocktail of as many as 250 short “mini” proteins, also called peptides.
MANDË HOLFORD: So, if you think of venom, think of it not as like a single bullet, right? It’s more like, I like to describe it as a cluster bomb. It’s a series of bullets coming at you, and each individual bullet has a target in the physiological system.
DAVID POGUE: Each venom peptide has evolved to mount a very specific attack, often acting as keys that fit a cell’s lock-like receptors. In the case of the nervous system, that can prevent a specific neuron from transmitting an impulse or, conversely, jam the neuron open, generating a flood of signals.
In the wild, all those targeted attacks paralyze the snail’s prey, but the precision with which the venom peptides act also means that they may have another role as medicines.
MANDË HOLFORD: And so, we study these venoms to try to figure out novel medicines for treating things in pain and cancer. Actually, they make great drugs because they’re highly specific, very fast-acting and very potent.
DAVID POGUE: A venom curing instead of killing? Wouldn’t be the first time.
There are currently at least seven drugs on the market developed out of the study of venoms. They include an anticoagulant derived from medicinal leeches and a diabetes medicine from Gila monsters. There’s even one already from cone snails, an analgesic to treat severe chronic pain.
MANDË HOLFORD: And it’s the exact peptide that you would find in the venom. It’s not a derivative of it, it’s not a small molecule, it’s exactly as nature expressed it in the animal.
JULIETTE GORSON: And I’ll just run a simple D.N.A. extraction.
DAVID POGUE: Mandë’s team has already made some major breakthroughs.
TANYA NAPOLITANO (Hunter College): So, I could do a nano-LC-MS and see what’s inside of here.
DAVID POGUE: In 2014, they identified a peptide from another venomous snail that attacks liver tumor cells, inhibiting their growth. It’s cutting-edge work that’s reaping the rewards to be found at the intersection of chemistry and biology.
MANDË HOLFORD: Learning how the venom is used more in ecological settings helps to further us in terms of how we understand how it can be applied for medicinal or therapeutic applications. And so, right now, it’s a fun time to be a venom scientist, because those worlds are colliding.
DAVID POGUE: In both chemistry and biology, change is a story told through reactions. And understanding those reactions has given us new insights into both our world and ourselves.
ED CUSSLER: If you lose that chemical reaction, two-billion people starve. This is not a hypothetical issue.
DAVID POGUE: And with that comes a lesson.
Oh, man!
Just as a molecule can act as both a venom and a medicine, or one reaction can both help feed the world and blow it to bits, our scientific knowledge is a powerful tool.
The power of bacon!
But it is up to us to learn how to use it well, as we continue to go Beyond the Elements.
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