 Hey everybody, if you've ever taken an introductory science class there is a point at the beginning of the course where your teacher basically drones on and on about what the subject is. I took biology and my bio teacher said what is biology and then he went on this five minute more festival about what biology was, my chemistry teacher did it, my physics teachers did it. So I'm going to do it to you. So this is probably the point where you're going to sit there and tune out and start texting your friends. So get your phone ready. All right. So what is chemistry? Apparently it has to do with this spilled bottle of table salt down there. It doesn't really, but I don't know, I left it there. Okay. This is taken from your book. It says chemistry is the study of the composition, structure, properties and reactions of matter. If that makes sense to you, great. It's a little bit stuffy to me. So I'm going to try to pick it apart in plain English. So let's move to the next slide. Chemistry studies matter. That was a word that was in the earlier definition, what's matter? Matter is the material world, physical things, things that we can touch and feel. So chemistry is interested in the stuff that we can touch and feel in the world. Chemistry studies the composition of matter. So what that means in English is what material objects are made of. As an example, what are different things made of? If you have a computer mouse sitting next to you, chemist might be interested in knowing what types of plastics went into it, what types of electronics went into it. If you have a cup of coffee, chemist might be interested in knowing what things go into making a cup of coffee. Obviously, there's a lot of water, but there are other things that go in there, too. So chemistry is interested in knowing what things are made of. Let's see. Chemistry also studies the structure of matter. Structure is basically a fancy word that means how things are assembled or how things are shaped. So chemistry is interested in how material objects are put together, how they assume certain shapes. An example of that is with water. Water at very cold temperatures turns into a solid, so it's shaped in a certain way. If you warm it up, if you look at water under the conditions that we usually live at, water is a liquid. So chemistry is interested in understanding why things have certain shapes under certain conditions. And obviously, if you heat up water enough, it turns into steam, turns into a gas, completely different shape. Another example of this might be why do snowflakes, which are made of water, why do they typically have six sides to a snowflake? Again, that is probably a feature of what water is made of, and chemists are interested in understanding how certain materials assume certain shapes. So that's called the structure of matter. Chemistry studies the properties of matter. That basically means that's, generally speaking, any feature that you can measure of a material object. I already told you that, basically, water is a solid at certain temperatures, and we usually call it ice. Water will melt, usually at about zero degrees Celsius. That's a temperature. If you're not familiar with degrees Celsius, we'll get to it later, but that is a feature of water. It usually melts at about this temperature. Water will boil, typically at about 100 degrees Celsius. Those are features of water. You might have an explosive object that might explode. That's my cartoon for explosion. I'm not sure why that's the cartoon, but there might be an explosive material that explodes at a certain temperature, or explodes only if you hit it with a certain amount of force. That might be a feature of an explosive object that chemists are interested in. So chemists are just interested in properties or features of material objects. And finally, chemists are interested in what I'm going to call reactions of matter. And reaction was, in the earlier definition, a couple of slides back, too. And basically, what a reaction is, is when you mix two different materials together, every once in a while, you might get a completely new material made. And when that happens, when two materials mix together to make you something new, that's called a chemical reaction. And we will talk about that in a little more detail as well. Basically, a chemical reaction is getting something new out of two materials when you mix them together. An example of that is shown in this picture over here that I'm circling. Here's a clear liquid in this cylinder. It's being poured into another clear liquid in this container down below. You would think that if you mix clear liquid number one with clear liquid number two, you would probably get just more clear liquid. But that doesn't happen. Little bit of a surprise, you get this yellow gunk that gets made. And because you get something maybe you wouldn't expect, you get a new material. I'm going to call that a chemical reaction. So chemists are interested in trying to figure out how different material objects interact or react with each other to make new things. Another example of that, just to bring something more realistic into the situation, is an iPhone. There's a lot of chemistry that goes into making an iPhone. I'll just focus on the front glass for the moment. The glass actually contains materials that make it harder for you to get your greasy fingerprints to stay on the glass. So in other words, to make the front of your iPhone look a little bit nicer, there are chemists who are involved in minimizing the amount of grease that ends up getting grease or oil that ends up getting stuck to the front face of an iPhone because of your fingerprints or because of the oil on your skin on your cheek when you press it up against your cheek to have a phone conversation. So there's chemistry there. Believe it or not, the glass on the iPhone is relatively difficult to break compared to traditional glass. So I know that a lot of you out there were successful in breaking the front glass on your iPhone. So you can give yourself a pat on the back. You defeated the chemists who were involved in making relatively difficult to break glass. But believe it or not, that glass is actually pretty difficult to break compared to traditional glass because it's so difficult to break it. Sometimes it's given the cutesy name of gorilla glass. And I guess the reason for that is if you are a gorilla and maybe if you're in a good mood, it might be difficult even for you to break the glass a little bit. But I'm sure if you tried, you'd still be able to break it because I've broken one or two myself over time. So that's it. That's what chemistry is. You can tune back in now. You can stop texting your friends, fold up the phone or turn it off or whatever, and I'll see you in a little bit.