WEBVTT

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What would you say

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is the most important discovery

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made in the past few centuries?

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Is it the computer?

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The car?

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Electricity?

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Or maybe the discovery of the atom?

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I would argue that it is this chemical reaction:

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a nitrogen gas molecule

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plus three hydrogen gas molecules

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gets you two ammonia gas molecules.

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This is the Haber process

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of binding nitrogen molecules in the air

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to hydrogen molecules,

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or turning air into fertilizer.

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Without this reaction,

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farmers would be capable of producing enough food

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for only 4 billion people;

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our current population is just over 7 billion people.

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So, without the Haber process,

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over 3 billion people would be without food.

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You see, nitrogen in the form of nitrate, NO3,

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is an essential nutrient for plants to survive.

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As crops grow, they consume the nitrogen,

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removing it from the soil.

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The nitrogen can be replenished

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through long, natural fertilization processes

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like decaying animals,

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but humans want to grow food

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much faster than that.

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Now, here's the frustrating part:

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78% of the air is composed of nitrogen,

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but crops can't just take nitrogen from the air

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because it contains very strong triple bonds,

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which crops cannot break.

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What Haber did basically

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was figure out a way

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to take this nitrogen in the air

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and put it into the ground.

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In 1908, the German chemist Fritz Haber

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developed a chemical method

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for utilizing the vast supply of nitrogen in the air.

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Haber found a method

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which took the nitrogen from the air

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and bonded it to hydrogen

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to form ammonia.

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Ammonia can then be injected into the soil,

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where it is quickly converted into nitrate.

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But if Haber's process was going to be used

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to feed the world,

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he would need to find a way

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to create a lot of this ammonia quickly and easily.

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In order to understand

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how Haber accomplished this feat,

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we need to know something

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about chemical equilibrium.

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Chemical equilibrium can be achieved

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when you have a reaction in a closed container.

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For example, let's say you put

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hydrogen and nitrogen into a closed container

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and allow them to react.

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In the beginning of the experiment,

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you have a lot of nitrogen and hydrogen,

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so the formation of ammonia proceeds a high speed.

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But as the hydrogen and nitrogen react

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and get used up,

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the reaction slows down

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because there is less hydrogen and nitrogen

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in the container.

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Eventually, the ammonia molecules reach a point

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where they start to decompose

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into the hydrogen and nitrogen.

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After a while, they two reactions,

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creating and breaking down ammonia,

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will reach the same speed.

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When these speeds are equal,

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we say the reaction has reached equilibrium.

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This might sound good, but it's not

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when what you want

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is to just create a ton of ammonia.

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Haber doesn't want the ammonia to break down at all,

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but if you simply leave the reaction

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in a closed container,

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that's what will happen.

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Here's where Henry Le Chatelier,

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a French chemist,

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can help.

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What he found was

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that if you take a system in equilibrium

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and you add something to it,

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like, say, nitrogen,

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the system will work

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to get back to equilibrium again.

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Le Chatelier also found

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that if you increase

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the amount of pressure on a system,

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the system tries to work

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to return the pressure it had.

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It's like being in a crowded room.

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The more molecules there are,

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the more pressure there is.

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If we look back at our equation,

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we see that on the left-hand side,

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there are four molecules on the left

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and just two on the right.

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So, if we want the room to be less crowded,

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and therefore have less pressure,

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the system will start combining

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nitrogen and hydrogen

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to make the more compact ammonia molecules.

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Haber realized that in order to make

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large amounts of ammonia,

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he would have to create a machine

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that would continually add nitrogen and hygrogen

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while also increasing the pressure

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on the equilibrium system,

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which is exactly what he did.

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Today, ammonia is one of the most produced

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chemical compounds in the world.

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Roughly 131 million metric tons are produced a year,

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which is about 290 billion pounds of ammonia.

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That's about the mass

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of 30 million African elephants,

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weighing roughly 10,000 pounds each.

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80% of this ammonia is used in fertilizer production,

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while the rest is used

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in industrial and household cleaners

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and to produce other nitrogen compounds,

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such as nitric acid.

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Recent studies have found

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that half of nitrogen from these fertilizers

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is not assimilated by plants.

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Consequently, the nitrogen is found

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as a volatile chemical compound

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in the Earth's water supply and atmosphere,

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severely damaging our environment.

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Of course, Haber did not foresee this problem

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when he introduced his invention.

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Following his pioneering vision,

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scientists today are looking

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for a new process of the 21st century,

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which will reach the same level of aid