Hello everyone, my name is Dr. Feiler and I'll be your professor for this course, Chem 151. And what you can see here is the slides that I'll be using to give these lectures. This is from a textbook called Introductory Chemistry by Nivaldo Tro. And it pretty much... covers the same material that is in your free text which you can have online.
But both the free text of course is available to you as well as the slides. These slides are on Canvas. Okay so let's get into chapter one and what it talks about.
So turns out that chemistry the way we defined it is to understand what matter does by studying what matter is made up of, which is atoms and molecules. And so by doing that, we can understand pretty much everything around us. Okay, so everything, including me, you, the tables, books, things like that, they're all made out of the one or more atoms or combination of atoms and all those atoms can be found in what's called the periodic table so this is a periodic table of the elements and you can see there's about a hundred different kinds of elements so we have carbon here nitrogen there oxygen and so on okay but all the known elements are found in this table and like I said everything including you and me are made up of one or more of these elements okay but where did all these elements come from okay turns out let's see let me start drawing here okay about 13.8 billion years ago there's something called The Big Bang, you probably have heard of it.
There was a popular TV show named after it called The Big Bang Theory. And what that theory says is that 13.8 billion years ago, the universe was very small, maybe the size of a grain of rice. And there was a Big Bang where particles, which...
I'm simplifying this a lot, but we'll just call them hydrogen atoms for now. So in the beginning, the universe was nothing more than hydrogen atoms, and I'm writing H for hydrogen. And what happened then, after some period of time, gravity, which attracts atoms to each other, started clumping all these hydrogen atoms.
into one location, so maybe that would be like this one over here. And when you have a bunch of hydrogen atoms in a very small space, well, it's not a small space, but it's a very large space, but they're very close to each other, that becomes what we know as a star. So, for example, our sun is a star, and in the center of our sun, There are a bunch of hydrogen atoms that are being crushed together under the force of gravity.
And when that happens, they're being turned into heavier atoms like helium. So you could take two hydrogen atoms, make a helium, heavier helium atom. And then you could take helium atoms and make carbon atoms, oxygen atoms. nitrogen atoms and so on.
Okay, so in the center of these stars, the hydrogen atoms are being fused together to make the other heavier atoms that we find in the periodic table. But then what happens, eventually the star, you know, after billions of years, will explode, okay? And when it explodes, it spits out all those...
heavier atoms that it made in the center of its in the center of the star, like the nitrogen and carbon, into the space around it, and then those atoms can accumulate to form things like planets. Okay, so our planet, planet Earth, we'll get into what it's made out of mostly in a second here, but things like silicon, oxygen, iron. and magnesium, okay?
So that could be found in, for example, our planet Earth and other planets as well. And then on those planets, life started evolving, and over, you know, millions and millions of years, eventually humans were able to evolve, and now we find... This is where we find ourselves on this planet. And what a chemist wants to do is to study all these different elements, find out what their properties are, and how they interact with each other.
So basically, in a nutshell, that is what chemistry is all about. Okay, so let's look at some... Objects like I said the planet our planet Earth Even though okay, so even though there are like hundred different elements All these elements are not found in the same abundance depending on where you're looking. So for example our planet Earth We can find all those elements in the periodic table, but the majority some of them are much more Abundant than others.
So for example and they're in our Planet Earth, the most abundant element is iron, found at 34.6%. And you might wonder where that is. It turns out that's in the center of our planet. The core of our planet is mainly made out of iron.
And then you may not know this, but rocks are made out of primarily silicon dioxide, which contains both silicon and oxygen. So that explains... those large abundances, and then rocks also contain magnesium.
Okay, so just those four elements make up about 92% of the planet Earth. Okay, and you might wonder about, you know, there's a lot of water in the oceans, H2, which is the formula for water is H2O. The hydrogen is very light.
So because of that, it doesn't, you know, rank too high in this list. Okay, and as far as the universe, because it started out as all hydrogen, it's currently about, you know, almost 74% hydrogen by weight and 24% helium. So we're just looking at the universe as a whole. You know, it's still mostly just hydrogen with some helium. Those two elements together make up about 98% of everything out there in the universe.
What about the human body? Okay, so it's very different. It has a very different makeup from either the universe or planet Earth. As you know, you know, we're made up of a lot of water, H2O.
So that's why we have a lot of oxygen in us and a lot of hydrogen. But also, we're carbon-based. Our DNA has carbon. Our proteins have carbon, fats, things like that, muscles.
So that makes up 18%. Nitrogen can be found in our DNA. That makes up 3%.
Phosphorus. Also found in our DNA, but only at 1% and in our bones we have calcium But that only makes up 2.4% so just these six elements make up almost 100% of what the human body is composed of So you can see it's very different from Planet Earth or the universe and many other things. Okay, so You don't have to know any of this for the exam.
I'm just trying to... you know, explain to you what chemists do and why we do it and, you know, hopefully pique your interest. And again, it's everything around us that's made up of atoms, including our cells. Okay, so now we're going to move on with the other slides in the Text and what I'm going to do is just you know jump around and go over what I feel is important and You know so I may not cover every slide, but I will cover Most of the slides okay, so atoms are very small.
You can't see them with your Naked eye you need very sensitive instruments And, yeah, two or more atoms bonded together make up what's called a molecule, okay? So we'll look at some examples, like right here. Okay, so here we have two examples of molecules, okay? This is a water molecule right here, okay?
So this is... This red sphere is an oxygen atom, and these two white spheres are hydrogen atoms. So it kind of looks like a Mickey Mouse head.
Have you ever been to Disneyland and you've seen these Mickey Mouse balloons? They kind of look like this. So that's what a water molecule looks like.
And you put enough of them together and you get this clear liquid that we know as... water at room temperature. Okay, and over here, this is a molecule of carbon dioxide. This black sphere is a carbon atom, and these red spheres, again, are oxygen atoms.
Okay, so we're being consistent with our colors. Every red sphere is an oxygen atom. Every black sphere, carbon atom. white spheres, hydrogen atoms.
Okay, so for example, Coca-Cola, mostly water, so H2O, but also that fizz and the bubbles in soda come from carbon dioxide, which is a gas at room temperature. So that's why it forms those bubbles. Okay, of course you have other things in the Coke, like sugar and...
caffeine but those are bigger and more complex molecules that we'll talk more about later okay let's see so i'm going to skip a few slides here okay so here's some more examples just showing that you know everything around us is made out of molecules and atoms and again here's a glass of like soda contains mostly water some carbon dioxide for the bubbles okay now this molecule is kind of big that's a molecule of caffeine the blue spheres are nitrogen black spheres carbon red spheres oxygen white spheres hydrogen And, yeah, this molecule here is a molecule of sugar, where it has carbon, you can see those black spheres underneath there, oxygen, and hydrogen, okay? But yeah, mostly just water. In the pencil, if you're using a pencil, it's made out of graphite.
I mean, the thing that you use to write is made out of graphite. These are all carbon atoms and in the graphite form they can slide easily over and under each other and be transferred to the paper leaving whatever you're writing on the paper. And then of course this is showing a strand of DNA which can be found in the nucleus of all your cells. And here we have one new color. That light blue, those are phosphorus atoms.
The dark blue... It's nitrogen, carbon black, oxygen red, and hydrogen white. Okay, alright, so let's move on.
Okay, so, yeah, this is Richard Feynman, and he said that one of the... Most important ideas in all of human knowledge was when we realized that all things are made out of atoms, which we didn't know until not too long ago, maybe only a hundred years ago. And now that we know that, that helps explain a lot of what we see going on. We're going to talk about the scientific method.
We use the scientific method to learn everything that we currently know. So the scientific method involves conducting experiments where we make observations or recordings, then coming up with a hypothesis, which is a tentative interpretation of what we observed, and then from that... we can come up with these laws, which only can happen if a hypothesis proves true over and over after many repeated experiments.
Okay, then it becomes a lot. And then what a theory does, it tries to explain what's actually physically happening. That's making that law true.
Okay, so let's look at an example. Okay, so let's take the zeroth law of thermodynamics, which says that heat is only transferred from a hot object to a colder object, and never the other way around. Okay, so if you have like two pieces of metal, that are the same size and same mass, made out of the same material, and you put them next to each other, and let's say, well, I tried to make them the same size, but let's say they were each at, well, let's say this first one was at 50 degrees Celsius, and this second one was at 100 degrees Celsius, and you put them next to each other, what you'll find is that the heat always moves from the hotter object to the cooler object. Okay, never from the cooler object to the hotter object.
So when you put them together, you don't find that, oh, this one moved down to 25 degrees C and that one moved up to 125 degrees C. You would never see that. Instead, what you see is that, yeah, this one will get cooler, this one... will get hotter and they're the same size material and if you leave them in contact for a while eventually you can probably guess that both of them would reach um yeah 75 degrees celsius okay which is just the average of both of them okay so that's called the zeroth law of thermodynamics he always moves from a hotter object to a colder object Okay, so you can conduct an experiment where you make an observation.
In this case, what was the observation? Recording the temperature. How could you record the temperature? Well, there's a few ways, but obviously with a thermometer.
There are different kinds of thermometers, optical, etc. But that would be how you could conduct this experiment, right? You could record the temperatures before you put them into contact with each other and their temperatures after you put them into contact with each other.
And that would be your experiment. And then you can, from the result of that experiment, you can come up with a hypothesis. Oh, the hypothesis would be that heat always flows from the hotter object to the colder object because that's what you saw. And then you would repeat similar experiments.
you know over and over again and then if you found that You know, that was always the case, that the heat moved from the hotter object to the colder object. You could promote that hypothesis to a law, okay? So the law, and that's actually what this is. This is the zeroth law of thermodynamics.
The first law is the conservation of energy. And then there's a second law, which has to do with... Entropy always increasing, but don't worry about those.
And you don't even have to worry about this one. This is just an example. But now what is, so let's go back to this slide here.
So we covered observations. That's the recording of a measurement during an experiment. A hypothesis is a tentative interpretation, and then a law is what a hypothesis is. hypothesis will be promoted to if after numerous experiments you see that hypothesis always being true.
But now what is a theory? Okay so the theory tries to use a model to explain why that's the case. Why does heat always move from the hotter object to the colder object?
And in this case we have to remember that you know everything is made out of atoms. So these blocks of, you know, let's say they're pieces of iron. They contain iron atoms. And depending on the temperature of the object, they're going to be kind of shaking around, jiggling around in place. Okay.
and the higher the temperature, the more that they're going to be jiggling. So it's true with this other piece of iron, but now it's at a higher temperature. So because it's at a higher temperature, its iron atoms are going to be jiggling around more violently.
And so then when you put them into contact, these guys are going to bump into these guys, and it's going to make them... start vibrating faster and then they're going to start bumping into their neighbors, make them start vibrating faster. So what happens? The temperature goes up and over here because these atoms are giving their energy to these atoms, the temperature here is going to go down.
Okay, so eventually after time, if they're the same size in material, they will equilibrate. Okay, so that's this is the theory that explains how these how this law actually takes place. Okay, so that's a theory.
It's a model explaining why this happens. None. Okay, the the law itself doesn't tell you anything about why that happens. It just says heat will always move from the hotter object to the colder object, but the theory explains why that happens.
Okay, so you should know. So all these things together are what's called the scientific method, where we have conduct experiments, make observations and measurements, come up with a hypothesis, promote them to laws, and then come up with a theory to explain that law. Okay, that's the scientific method, and that's the way we learn everything that we know. And then we can publish these ideas into journals and then other people can read about them. That's the way we spread the information Okay, so let's move on Okay, so the rest you can read on your own But yeah, that's those are the main takeaways from chapter one.
So, okay, that's it for chapter one, and I will see you in chapter two. Bye.