Chapter 2: Building Blocks of Materials

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Welcome to the Deep Dive.

And today, we are actually doing something a little different, a little special just for you.

Yeah, we're basically treating this as a personalized one -on -one tutoring session.

Just you and us.

Exactly.

Our mission today is to help you completely master the foundations of general chemistry.

So we are pulling strictly from chapter two of your textbook, Chemistry, Human Activity, Chemical Reactivity.

Right, the second edition.

And chapter two is all about the building blocks of materials.

Which I know sounds like standard textbook stuff.

But before we get into the math and the molecular models, we're actually going to look at how these exact foundational principles were used to take down one of the most famous athletes in human history.

Oh, this is such a great story.

It really is.

I mean, we're talking about Lance Armstrong, who had his seven Tour de France titles stripped in 2012 by the US Anti -Doping Agency.

And Floyd Landis, who won in 2006 and then lost his title right after stage 17.

Yeah, and the crazy part is the ultimate witness against these guys wasn't a hidden camera or an informant.

It was literally a microscopic variation in a single invisible atom.

Which is just wild to think about.

To catch these cheating cyclists, you can't just look at how fast they pedal.

You have to look under the hood at the chemical level.

Right, because anti -doping chemists have to constantly differentiate between two completely different sources of substances in an athlete's body, endogenous and exogenous.

Right, so endogenous substances, those are the ones produced naturally inside the human body, right?

Exactly.

I mean, your body is essentially a giant chemical factory.

It takes the food you eat and transforms it.

So testosterone, for example, is an endogenous hormone.

Your body naturally synthesizes it using cholesterol from your diet.

Okay, and then exogenous substances are the ones introduced from the outside,

like designer drugs synthesized in a lab somewhere.

Yes.

And if an athlete takes a purely exogenous drug, something that is totally alien to the human body, like that infamous steroid they called the CLEAR back in the day.

Oh right, THG.

Yeah, THG.

Well, catching that is relatively straightforward.

You take a urine or blood sample and you run it through a machine called the GCMS.

Which stands for gas chromatography, coupled with mass spectrometry, right?

You got it.

The gas chromatograph separates all the different compounds in this complex mixture of urine and then the mass spectrometer analyzes the structure of the molecules.

And it just compares them against a database of banned stuff.

Exactly.

If the CLEAR is in there, the machine just flags it.

Simple as that.

Okay, but let's unpack this for a second because this is where I always get tripped up.

What happens when an athlete takes a lab -made, exogenous version of a drug that is also endogenous?

Ah, right.

The testosterone loophole.

Right.

Because if testosterone is already naturally floating around in an athlete's body, how do you prove they took extra?

You can't just point to the vial and say, look, testosterone.

I mean, their natural baseline might just be super high, especially for an elite athlete.

And athletes definitely exploited that for years.

So initially, testing agencies tried to solve it by looking at ratios.

They looked at the TE ratio.

Which is testosterone compared to epitestosterone?

Right.

Epitestosterone is just another naturally occurring steroid.

In a normal person, that ratio hovers right around one to one.

So the agencies decided, well, if an athlete's ratio spikes over 6 .0, that's an automatic flag for doping.

But you know, athletes are nothing if not incredibly competitive problem solvers.

So they figured out, hey, if the test only cares about a ratio, I'll just take exogenous epitestosterone alongside my exogenous testosterone.

Exactly.

They artificially inflated both sides of the scale to keep the ratio perfectly balanced.

Which is so sneaky.

But it forced anti -doping chemists to abandon the fluids entirely and look significantly deeper.

They had to look at the atoms themselves.

And to understand how they trapped Floyd Landis, we need to build your foundation on how chemists view matter in the first place.

OK.

So this brings us to what the textbook calls the kinetic molecular model,

which, honestly, the name always intimidated me a bit.

It sounds complicated, but it's really just a way of explaining why solids are solid, liquids are liquid, and gases are gas.

It all boils down to two competing forces.

Right.

Because the model assumes all matter is made of unimaginably tiny particles that are constantly moving.

Right.

That motion is their kinetic energy.

But at the same time, these particles experience an electromagnetic attraction to each other.

So it's this microscopic tug of war between the desire to fly around and the sticky attraction pulling them together.

So let's use an ice cube as an example.

In a solid ice cube, the attractive forces are winning.

I used to picture the molecules in a solid just sitting there, completely still.

But they aren't, are they?

Not at all.

They are locked tightly into a regular array so they can't move past one another, but they are vibrating frantically right in place.

And then if you take that ice cube out of the freezer and put it on the counter, you are adding heat.

And heat is just a measurement of kinetic energy, right?

You're giving the particles more energy to fight back against those attractive forces.

Eventually they vibrate so violently that they break their rigid structure.

And they start slipping past each other.

That is the precise mechanism of melting.

The substance is now a liquid.

They're still held close together by attraction,

but they have enough kinetic energy to be fluid.

They can tumble and flow.

And then if you put that liquid water in a kettle and turn on the stove, you are pumping in so much kinetic energy that the particles finally just tear free entirely.

They fly apart, moving at breakneck speeds, colliding with each other.

Now it's a gas.

And a gas will expand infinitely to completely fill the volume of whatever container it's in.

Right.

But in the real world, whether we're talking about the air we breathe or a cyclist's urine sample, we're rarely dealing with just one pure substance.

We're dealing with mixtures.

Yes.

And the key distinction chemists make is how well those mixtures are blended.

If you can clearly see the different constituents like sand mixed with water, that is a heterogeneous mixture.

But if the blending is completely uniform down to the microscopic level, you have a homogeneous mixture.

Which chemists usually just call a solution.

And we naturally think of solutions as liquids, right?

Like stirring salt into water.

But air is actually a gaseous solution of nitrogen and oxygen.

Yeah, even a solid can be a solution.

Like brass, which is a uniform blend of copper and zinc.

Okay, so to navigate all this, to take a complex solution like an athlete's blood and figure out if there's synthetic testosterone hiding inside, chemists have to operate on three different levels of reality simultaneously.

The three levels of chemistry.

The first one is the observable level.

This is the macroscopic world.

It's what you can see, smell, touch, and measure in a lab.

So like knowing that pure testosterone is a creamy white solid that melts at exactly 155 degrees Celsius.

Exactly.

The second is the molecular level.

This is the realm of the invisible.

It consists of the mental models chemists build to understand how those particles are interacting and colliding.

So the observable level is me physically drinking a glass of water.

The molecular level is me closing my eyes and imagining those little Mickey Mouse -shaped H2O particles tumbling over each other.

A perfect way to visualize it.

And the third level is the symbolic level.

This is the language of chemistry, because we can't draw millions of Mickey Mouse molecules every time we write an equation.

Right, that would take forever.

So we write it down using symbols.

We write H2O with a tiny L in parentheses to communicate liquid water.

Or C19H2802 with a tiny L for solid testosterone.

A good chemist is basically a translator consciously jumping between all three levels.

So let's zoom in on that molecular level for a moment.

What are these particles actually made of?

This is where the textbook makes a really important distinction between an element and an elemental substance.

It's vital because people often confuse the abstract idea with the physical reality.

An element simply refers to a specific type of atom, like oxygen or bromine.

But nature is highly interactive.

Atoms of a single element rarely exist all by themselves.

Right, so the elemental substance is what you actually interact with.

If I take a deep breath, I'm not breathing in single lonely oxygen atoms, I'm breathing in molecular oxygen O2.

Exactly.

Bromine atoms pair up to form Br2, which is actually a dark red liquid at room temperature.

Phosphorus travels in little pyramids of 4, written as P4, sulfur is S8.

But the real magic happens when atoms of different elements combine.

When two or more different elements bond together in very specific fixed proportions, they create a chemical compound.

And when they form a compound, they don't just blend their traits like mixing red and blue paint.

They undergo a total identity shift.

This part always blows my mind.

The textbook uses iron and sulfur to show this.

If you take shiny iron chips and yellow sulfur powder and just stir them together in a bowl, you've made a mixture.

Right, and you could literally drag a magnet through that bowl and pull all the iron right back out.

Because in a mixture, the elements retain their individual physical properties.

But if you apply heat and force them to chemically bond, they form a compound called iron pyrite.

Fool's gold.

It forms these perfect beautiful golden cubes that look absolutely nothing like iron or sulfur.

And if you hold a magnet to it, nothing happens, it's a completely new substance.

That fundamental transformation is a chemical reaction.

And we track that at the symbolic level using chemical equations.

Like let's look at the combustion of natural gas, methane.

Okay, so the equation is CH4 gas plus 2 O2 gas molecules reacts to form CO2 gas plus 2 H2O gas molecules.

The substances you start with, the methane and the oxygen, are your reactants.

And the new things you create, the carbon dioxide and water vapor, are your products.

But notice what happens to the atoms themselves.

They aren't destroyed, no new atoms are created.

On the reactant side, we have one carbon atom, four hydrogens, and four oxygens.

On the product side, we still have exactly one carbon, four hydrogens, and four oxygens.

It is a strict ledger.

The atoms just got dismantled and snapped back together into new configurations like Lego bricks.

Which beautifully illustrates the difference between physical properties and chemical properties.

A physical property is something you can observe without changing the substance's identity, like melting ice.

It's still water.

But a chemical property, like reactivity or combustion, describes the actual reactions a substance can undergo.

To see methane combust, you have to fundamentally destroy the methane.

So we know elements combine to form all the materials in the universe.

But what fundamentally makes an atom of carbon different from an atom of oxygen?

To answer that, we have to look inside the atom.

Right, the subatomic particles.

Based on those early 1900s experiments by Thomson and Rutherford, we've got protons which are positive, neutrons which are neutral, and electrons which are negative.

And the scale of how they fit together is staggering.

The textbook asks this great question.

It says, if a potassium atom was expanded to the size of a massive 200 -meter football stadium, how big is the nucleus?

What are we talking here?

Like a beach ball on the 50 -yard line?

Vastly smaller.

If the atom is a football stadium, the nucleus containing all the protons and neutrons is about the size of a single glass marble sitting on the 50 -yard line.

Wait, really?

A marble?

But the protons and neutrons have almost all the mass of the atom.

Yes.

They are incredibly dense.

That tiny marble contains over 99 .9 % of the entire atom's mass, which means the rest of the stadium is overwhelmingly empty space.

That's a cloud of near -massless electrons whizzing around.

And they stay there because the positively charged protons in the nucleus act like an anchor holding the negatively charged electrons in orbit.

Exactly.

And in a neutral atom, the number of negative electrons perfectly matches the number of positive protons.

And that number of protons is the single most important defining feature in chemistry.

The atomic number, Z.

It's the ultimate ID badge.

One proton means you are hydrogen, period.

At a second proton, you are helium.

The protons dictate the element.

But this brings us right back to Floyd Landis and the doping scandal.

Because while every atom of an element must have the exact same number of protons, nature is a little more flexible with the neutrons.

Right.

Atoms of the exact same element that happen to have different numbers of neutrons are called isotopes.

And this was the smoking gun.

Every carbon atom in the universe has six protons.

But about 98 .89 % of natural carbon also has six neutrons.

That's carbon -12.

But a tiny sliver of natural carbon, about 1 .11%, happens to have seven neutrons.

That is carbon -13.

And an even tinier fraction has eight.

And what's fascinating here is that those tiny extra neutrons are exactly what caught Floyd Landis.

They don't change how the carbon reacts chemically, but they do make carbon -13 slightly heavier.

And here's why that matters.

The exogenous synthetic testosterone used in doping was manufactured using chemical starting materials from soy plants.

But human endogenous testosterone is built from cholesterol, which comes from a mixed human diet.

And because of biology, soy plants have a slightly lower concentration of that heavy carbon -13 isotope compared to a normal human diet.

So anti -doping chemists took the testosterone from the urine sample, burned it into carbon dioxide gas, and measured the ratio of carbon -13 to carbon -12.

And when they saw that abnormally low amount of carbon -13, it was undeniable proof that the testosterone was a synthetic plant -based drug.

The invisible isotope's literally testified against him.

It's brilliant.

But to pull that off, chemists needed an incredibly precise tool.

You can't put an atom on a bathroom scale.

You need isotope ratio mass spectrometry.

Which means using a mass spectrometer.

And I really want to understand how this machine works because weighing something that is mostly empty space sounds impossible.

It relies on momentum and magnetism.

First, you take a gas sample and shoot it into a vacuum chamber.

You bombard it to knock an electron off each atom, which ionizes them, giving them a plus -one charge.

And because they're charged, they react to a magnetic field.

Precisely.

You shoot this beam of charged atoms down a tube that curves through a powerful magnet.

The magnet pulls on the passing atoms, bending their flight path.

Oh, I get it.

It's like a sports car in a heavy semi -truck trying to take a tight corner at the exact same speed.

The lighter sports car, the carbon -12, gets pulled into a tight curve.

But the heavy semi -truck, the carbon -13, has too much momentum and swings wide.

Exactly.

And by measuring exactly where they hit the detector board at the end of the curve, chemists can calculate their exact mass and how abundant each isotope is.

Which is vital, because when you look at the atomic weight on the periodic table, you aren't looking at the weight of a single atom, you're looking at a weighted average of all the naturally occurring isotopes.

Right.

Let's look at worked example 2 .3 from the textbook.

It walks us through calculating bromine's atomic weight.

Bromine is basically a 50 -50 split in nature.

Right.

Between a lighter isotope and a heavier one.

Exactly.

So you take 50 .69 % of the lighter isotope, which weighs 78 .918 Mu.

Okay, that gives you about 40 .00 Mu.

And you add that to 49 .31 % of the heavier isotope, which is 80 .910 Mu.

Which is about 39 .90 Mu.

So you add those together and get 79 .90 Mu.

Which is exactly the number on the periodic table.

Yes.

But here is the thing.

Doing actual chemistry requires counting.

If you're making a pharmaceutical, you need billions of atoms reacting in exact proportions.

But we can't count microscopic atoms by hand.

We have to weigh them in grams.

So how do we translate a weight in grams into a count of atoms?

We use the ultimate counting unit, the mole, spelled M -O -L -E.

This is where it gets really interesting.

A mole is literally just a chemist's dozen.

When you say a dozen, everyone knows you mean 12.

The mole is the exact same concept.

It just represents a specific number of things.

It's just an unimaginably large number.

Amedeo -Avogadro's constant, 1 mole equals 6 .0221414 times 10 to the 23rd power particles.

That is a 6 followed by 23 zeros.

So a mole of carbon is 6 .022 times 10 to the 23rd atoms of carbon.

And here is the elegant part.

The mass in grams of 1 mole of any element, its molar mass, is numerically identical to its atomic weight on the periodic table.

Wait, really?

So if carbon's atomic weight is about 12 amu, 1 mole of carbon weighs exactly 12 grams.

Exactly.

It's a mathematical skeleton key.

The formula is amount in moles equals mass in grams divided by molar mass.

Let's do worked example 2 .4.

So you have 2 .50 moles of lead.

How much does it weigh?

OK.

So I look at the periodic table.

Lade's molar mass is 207 .2 grams per mole.

I multiply my 2 .50 moles by 207 .2 and I get 518 grams of lead.

Perfect.

Or going the other way, worked example 2 .5, if you have 36 .5 grams of tin, how many moles is that?

Tin is 118 .7 grams per mole, so I divide my 36 .5 grams by 118 .7 and I get 0 .308 moles of tin.

It's actually really simple once you see the pattern.

It is.

The textbook even takes it a step further with mercury using density.

If you have 32 .0 milliliters of liquid mercury and its density is 13 .534 grams per milliliter.

Ah, OK.

First I have to find the mass.

Volume times density.

So 32 .0 times 13 .534 is 433 grams.

Then divide that by mercury's molar mass, which is 2 .6, and I get 2 .16 moles.

You've got it.

And why do we care about all this math?

Because to make products safely and efficiently, we need exact ratios.

And weighing them in grams is the only way our observable hands can count those molecular atoms.

Which is why the periodic table is so crucial.

It's the ultimate cheat sheet.

It's organized into vertical columns called groups for elements with similar properties and horizontal rows called periods.

It also visually separates metals from non -metals with a diagonal line from boron to tellurium.

Metals conduct electricity, non -metals generally don't.

Though carbon in graphite form is an exception.

Right.

Right.

But there's a recent update to the table that IUPAC just made.

The periodic table of the isotopes.

Yes.

Because of those mass spectrometers getting so precise, chemists realized that for some elements the ratio of heavy to light isotopes isn't a universal constant.

It actually varies depending on where on earth you dig the sample up.

Exactly.

Elements with high variation like carbon, hydrogen, oxygen, and bromine are now colored pink on this table.

They show an interval of possible weights.

Elements with one stable isotope like fluorine are blue.

Which leaves you with a pretty provocative thought.

I mean, all the complexity in the universe from water to sophisticated doping rings comes down to just 90 or so elements defined by the number of protons in a tiny microscopic nucleus.

But if atomic weights aren't fixed constants,

what other fixed rules of nature might we have to rewrite as our instruments get more precise?

It's a fascinating question to ponder.

Thank you for joining us from the Last Minute Lecture Team.