chemistry and matter that's what we're going to be discussing in this first lesson in my brand new high school chemistry playlist uh we're going to be releasing videos weekly throughout the 2020 2021 school year uh covering 16 chapters in what is typically presented in your average high school chemistry course so whether you're in high school whether you're being homeschooled whether you're doing online school in the middle of the pandemic i hope you find these helpful and if you'd like to be notified every time i release one of these uh subscribe to the channel and click on the bell notifications and if you're interested in the study guides that go with these lessons or practice materials for the course check out my premium course on chatsprep.com all right so let's dive right in and let's talk about what is chemistry so chemistry is really just a study of the interactions between matter and energy that's simply what chemistry is and it's a very simple demo you know definition here but it's much more complicated in this right so if you look chemistry is often referred to as the central science and what that really means is chemistry kind of connects biology with physics and you hear some people say that biology is really just a bunch of chemistry when you look down into it things of disorder chemistry is the foundation of all biology and that makes us chemists feel really good yeah you biologists you're just doing a bunch of chemistry it's really all about the chemistry so uh and there's some truth there you know biology the study of living systems and things of this sort if you look at it at the molecular level it's just a bunch of interactions and chemical reactions going on inside cells and things of the sort and so biology can be reduced to a bunch of chemistry so but then the physicists come along and they say yeah but chemistry is really at its basic levels just a bunch of physics and physics likes to look at everything in the context of four fundamental laws like gravity or the interaction between plus charges and minus charges and things of this sort well it turns out the vast majority of chemistry really can be reduced to the interaction of plus and minus charges which is really mind-boggling that much of it really reduces down to that simple principle and so in a sense chemistry really does reduce down to a bunch of physics so but we do study these disciplines separately and we're going to study this chemistry which kind of is right in the middle and connects the other sciences together so chemistry is the study of matter and energy and how they interact with one another and we can break it up into a number of different disciplines and stuff like this and for a typical high school or college freshman course we might call it general chemistry so but the truth is that's actually kind of a generic term for it it's actually would be called properly inorganic chemistry but for inorganic chemistry to make any sense we actually got to define organic chemistry first and organic chemistry is a course taken on the path to med school and things of this sort and it often is uh you know got some wincing with pain associated with it as well we call it ochem for short and organic chemistry has nothing to do with like not using pesticides and natural best growing practices or anything like that organic chemistry actually is all about the element carbon it turns out that the vast majority of living systems the fundamental elemental building block of all the lovely macro molecules involved in living systems are all based on carbon and so there's an entire branch of chemistry devoted to just looking at carbon-based compounds and that's organic chemistry and therefore inorganic chemistry is then all the other elements so the chemistry of all the other elements that's inorganic chemistry and you can take an advanced course in inorganic chemistry as like a senior in college so but when you're taking high school chemistry or general chemistry as a freshman in college you're really taking a course in inorganic chemistry now some of the other branches would be like analytical chemistry which is really looking at chemistry as like kind of an analysis tool like doing titrations to figure out acid content in a can of coca-cola or something like this so as an analytical tool so there's that there's also what's called physical chemistry and physical chemistry is a bad word just so you know so often called p chem for short there uh you'll see a bumper sticker here and there from different universities that says i survived peak hem because it's that bad so typically to take a course in physical chemistry you've got to have calc 1 cal 2 calc 3 a little bit of differential equations and linear algebra wouldn't hurt as well and maybe even some mathematical modeling software proficiency all those would be very helpful so it's very math intensive a little bit of a pain in the butt of the course truly fascinating truth be told but very math intensive and lots of students struggle with pcap and then the creme de la creme of chemistries at least in my book is biochemistry and biochemistry is the chemistry of living systems it is taking biology and looking it all the way down at like the molecular and atomic level and it is fascinating when you look at a little cell so that all living things are made up of that cell is actually a ginormous city so and there's factories in this city and and things of this sort and there's information processing going on the city it really does look like a little city when you look at it at that molecular level so and that study is actually what we term biochemistry and for me that's actually the most fascinating part now i like inorganic chemistry and i like organic chemistry but i love biochemistry it truly is fascinating mind-boggling when you see the complexity and the beauty going on inside each and every living cell inside your body so now we're really ready to bring begin this first lesson in high school chemistry proper so and to start this off we got to talk about what's the matter wait a minute wrong question my bad that's psychology what's the matter uh what is matter that's the question we're looking at and that's not the last lame joke you'll hear so what is matter so we talked about chemistry as being the interaction of matter and energy and you probably have a little bit of idea what energy is but what in the world is matter well simply put matter is anything that has mass and occupies space that's our lovely working definition so has mass now mass is a little bit of a technical definition but we'll kind of liken it to weight for the time being as long as you live on the surface of the earth you're probably going to encounter mass and weight as being equivalent now because all of us or almost all of us spend almost our entire lives or our entire lives on the surface of the earth why wouldn't we equate them because if you go to the moon you'd actually see a difference between mass and weight than how they were defined on earth things of this sort so but for now we're just going to liken it to weight it's definitely a very related to weight but not quite the same thing we'll see a better definition a little bit further down the road but matter is anything that has both mass and occupies space so that's matter and if you look at the fundamental level all of matter if you get small enough is made up of these little spheres at least we like to model them as spheres so called atoms so and these atoms come in 118 different types and those 118 different types are just types of different elements so these little atoms these little spheres so are just different types and these different types have different masses associated with them different sizes associated with them things of this sort so and basically we can take all sorts of different combinations of these different types to make the different substances compounds that exist uh in the universe and things of this sort so this is our study of chemistry so again it's matter so has mass occupies volume and at the fundamental level the basic building block of all matter is going to be the atom and these atoms come in 118 at least that's our current count so they keep discovering new elements but we're kind of reaching some you know somewhere near the limits but right now we've got 118 at the time of this filming that may grow a little more over time now in any discussion of matter we've got some vocabulary we use to describe the different properties of matter and so it turns out there's two fundamental types of properties for matter there are physical properties and there are chemical properties and if you change one of those physical properties we'll call it a physical change and if you change one of those chemical properties we'll call it a chemical change and so we've got to talk about what these physical properties are so a physical property is simply something about the physical nature of the matter you're looking at it could be the shape it could be the color it could be the size things of that sort so and most commonly the one of the big ones we like to talk about in chemistry is what phase of matter you have or sometimes what state of matter and the three most common examples of that are solids liquids and gases and i will assume that you actually kind of have a general idea what a solid a liquid and a gas are but we will explore those different phases in quite a bit of detail later on in this course now a chemical property on the other hand doesn't necessarily deal with kind of the physical features of it but the chemical behavior and so the chemical behavior deals with like undergoing chemical reactions and so when substances other undergo chemical reactions big thing you should realize is it produces new chemical substance the chemical substance you start with is different than the chemical substance or substances you end with when you undergo a chemical change and the properties associated with those chemical changes are called chemical properties and so good example this might be like flammability and so flammability is a chemical property how flammable something is and the reason that is is because burning something is actually a chemical change when you burn something you're actually combining it with the oxygen in the air around you to create new chemicals that you didn't start with so you're taking whatever you're burning plus oxygen and creating new chemicals so because they're changing their chemical identity that's a chemical change and so we might call combustion or burning something a chemical change and the property associated with that might be called flammability now if you look there's another example on there of a chemical change we've got oxidation and oxidizability might be the associated chemical property so now oxidation is something we'll cover a little bit later but involves the loss of electrons which we haven't even talked about which is why we're not going to really dive into it so but i did want to provide you with a second example there now again physical properties and physical changes we talked about you know shape and color and stuff like this so if i take this lovely study guide i'm doing here rip it in half so in that case that is a physical change i've changed like the shape of it and the size of it and stuff like this but the paper here is made of cellulose and that chemical identity still being cellulose has not changed so that is not a chemical change just a physical change all right let's get this lined up again cool so some of the physical changes then uh if if a state of matter or a phase of matter solid liquid gas is a physical property well again changing the phase of matter would be an example of a physical change so when i turn a solid into a liquid when i melt something or turn a liquid into a gas when i boil something those are examples of also physical changes i'm not changing the chemical identity of a substance i'm just changing the phase of matter in which it exists uh other examples might be like salt dissolving in water it turns out when salt dissolves in water you still have salt and you still have water their chemical identities have not changed and so we classify that as a physical change and i want to bring that up one up in particular because it's a little bit of a tricky example students are often kind of coerced into thinking that maybe that's a chemical change but it turns out it's just a physical change no substances have changed their chemical identities so another example i want to bring up of a chemical change and it actually goes hand in hand with oxidizability and that's when like a nail or a piece of iron or steel rusts and it turns out it's actually combining with oxygen to form a new substance iron oxide so iron combines with oxygen to produce iron oxide so your starting substances and your final substance are not the same and that's evidence that a chemical change has taken place so something rusting definitely turns out that's an oxidation it turns out and definitely an example of a chemical change that commonly shows up on a chemistry exam all right some more vocab here we've got to talk about elements and compounds and typically if you've got any substance in the universe it's either an element or it's a compound so any single substance so if it's an element it's really just a sample that contains only one element so all the atoms in that sample are just going to be the same element so you can have essentially i've got a several examples let's say pure sodium metal and so turns out sodium metal it is a metal but it turns out it's got a kind of a weak consistency and you might be able to if you've got a sharp knife slice it like butter not quite the consistency of butter but you'd be able to slice it with a sharp knife things of that sort that's pure sodium metal you might also have other examples but there are like silicon or hydrogen and i also put s8 a more complicated one so it turns out that some of those elements instead of coming one by one in a sample it turns out they they form what are called molecules combinations where they come two by two so like hydrogen here and hydrogen's an example what we call a diatomic and you're supposed to actually know those seven diatomic so i'm going to introduce them here but you will see them again somewhere along the way and so there are seven diatomics and conveniently enough on your periodic table six of them form a nice outline of a number seven so if you look you got nitrogen n2 oxygen o2 fluorine f2 chlorine cl2 br2 uh for bromine and i2 for iodine and they form a nice number seven on the periodic table and then hydrogen is the seventh one and again as a typical student you're expected to know oh most the elements come one at a time but those seven come as diatomics and they come two by two by two and we use that little subscript to identify that cool some people use a little mnemonic here to memorize that as well and they say never have fear of ice cold beer or something along those lines and personally i like just looking at a periodic table and seeing the number seven because you're always going to have a periodic table in front of you so you got one in your textbook you'll see them on the walls of classrooms you'll see them on socks you'll see them on ties you'll see them on tattoos it's terrible so but odds are you are going to have a pair of table accessible at all times and so if you can look at a periodic table and identify where those seven so diatomics are located great help you memorize them cool it turns out there are some that are like sulfur here that are even octatomic here so that's kind of rarity there's not like a bunch of these i can't name another one for you it just turns out like the most common form of sulfur is octatomic that's not usually something we make you memorize i just want to make you aware that coming one by one or two by two is not the only option but they are by far hands down the most common options so those are elements now a compound is still a single substance so but it is made up of multiple elements and so if you look at the examples on your hand out there so here we've got carbon dioxide the same stuff you're exhaling right now along with me so and it's a combination it's a single substance but it's got carbon and oxygen combined and it turns out it's in a set ratio a one to two ratio between carbon and oxygen atoms so but it is still made up of multiple different types of elements as a single substance that's what a compound is so some of the other examples i put on there are sodium chloride or sodium bicarbonate so water is another example not on your handout but we'll stick it up there h2o so any one of these is a single substance that's made up of more than one element and it could be two elements like these three or it could be like four different elements like sodium bicarbonate there and stuff like that so uh but again all examples of compounds well let's move on to the back side of this page so the next bit of vocab we've got are pure substances versus mixture and so again any substance in the universe is either going to be an element or a compound and so a pure substance is any single element or any single compound so if you look on your hand out there so we've got o2 here and i specially said o2 gas which we often represe represent the uh phase of matter here with a little slrg in parentheses to represent that solid liquid or gas so here's o2 gas and it is just a single element it's diatomic and that doesn't matter it's still just one type of element here oxygen and so that's a pure substance it's a single element but it could also just be any single compound as well and so notice the next one on there i've got water and as long as it's not got anything other than water present that's a single pure substance as well so any single element or any single compound that's a pure substance where as a mixture a mixture just has to have more than one substance and that could be more than one element like you see in air so the air you're breathing right now is like 78 percent nitrogen and 21 oxygen so mostly a mixture of two diatomic elements now technically there's a little bit of carbon dioxide in there because you're breathing that out and there's trace amounts of other gases there as well and so the truth is not just really two elements there's also a compound in there and there's even a couple of other elements and compounds that are again present really trace amounts uh in air but air is a good example of a mixture because it's not a single substance it's at least three substances plus even a few more another example would be salt water let's write that proper so salt water it has both salt which is sodium chloride it turns out and it has water and they're combined together so they're mixed together even the way we use that kind of belies the fact that it's a mixture but you've got more than one substance so in this case it's two compounds in the example above it started out as two elements but then even a third compound was in there but it doesn't really matter if you've got two elements or two compounds or one compound and one element or more than even two substances as long as you've got two or more substances together that is now a mixture so if you've got any one element or any one compound that's a pure substance but two or more elements or compounds that's now a mixture so now we've identified mixtures the next bit of vocab talks about the two different types of mixtures and we've got homogeneous mixtures and heterogeneous mixtures and you might already know that the prefix homo means the same and hetero means difference so and that's kind of at the heart of the definition here so a homogeneous mixture so it has uniform or the same comp composition throughout the entire mixture whereas a heterogeneous mixture has a different combina composition throughout the mixture so again a mixture means you have more than one substance and the question is is it uniformly mixed so it means if you take a sample of that mixture anywhere you take a sample if it would have exactly the same composition of the different components in the mixture well then that's going to be a homogeneous mixture so a good example here would be milk so when you've got a lovely bottle of milk oftentimes you'll even hear it called homogenized milk right and so it just belies the fact that it is a homogeneous mixture and so no matter where you take a sample of that milk the different components that are present will always be present in exactly the same composition that's a homogeneous mixture another good example would be salt water sometimes because we're going to find out when we get over to heterogeneous mixture here i'm gonna put salt water over here as well and so sometimes salt water mixture of salt and water can be a homogeneous mixture and sometimes it can be a heterogeneous mixture and you definitely want to understand in which cases is it one versus the other so again we're going to heterogeneous mixture here and here this is now a mixture where you do not have a uniform composition throughout and the simple example i'll give you is a pizza so let's say i give you a supreme pizza and are you guaranteed to get a piece of pepperoni in every bite or an olive in every bite or a sausage in every bite or a green pepper and everybody no some bites you'll get green pepper and sometimes you won't some you'll get an olive and some you won't the composition is not the same throughout that pizza so that's a good example kind of you know big macro example non-chemistry example of a heterogeneous mixture now one other way to kind of distinguish these is usually if you've got a homogeneous mixture it might be actually difficult to tell that you even have a mixture so oftentimes you'll see this used very commonly as a solution so in a solution is usually a mixture between a liquid and some other components in it and you can't tell even necessarily that there's other components in that liquid and so a solution is definitely by far the most common example of a homogeneous mixture now a heterogeneous mixture you can totally tell that you've got multiple components in there and stuff like this so if you look on your hand out there we've got vinegar oil salad dressing that's a great example now if you've got vinegar oil salad dressing so note that the vinegar is dissolved in water so but the oil is a whole separate layer and notice let's say you just take a bottle of vinegar oil salad dressing and you take a straw and you sip it take a little sip from the top and then you put the straw all the way down to the bottom and take a little sip they're going to taste very different those two samples so because in one you're going to get more of the vinegar side of things and one you're going to get more of the oil side of things and that's why every time you want to use that vinegar oil salad dressing got to shake it up really good to make sure it's mixed but notice what happens as soon as you stop mixing it well those two layers separate back out and that's one of the hallmarks or one of the ways to kind of identify a lot of heterogeneous mixtures is that they will separate out and form you know separate layers and that's definitely an evidence that you've got a non-uniform composition throughout the mixture and stuff like that a can of paint would be another good example and for the same reason if you notice when you go down to home depot or lowe's or something to buy some paint so they put it in this big fat mixer and it's going to stay good and mixed for a little while but even then you still got to take a stir home and once you open it stir it real well because just like the vinegar oil salad dressing it likes to separate out the different components that are in that paint because it is a heterogeneous mixture and so before you use it you got to mix it up because as soon as you stop mixing it will slowly start separating back out again betraying the fact that it's got a lack of uniformity in the composition cool so let's go back to that salt water example now that we've got listed under both so turns out salt's pretty soluble in water that means you can put a whole lot of salt and water and it'll all dissolve but only up to a point and again you can put a lot of salt in water at most temperatures and get it all dissolved now as long as you're got all that salt to dissolve in the water that's going to be an example of a homogeneous mixture and it turns out when you reach that maximum level that could possibly dissolve we call that a saturated solution and before you reach that point we'll call that an unsaturated solution so if we've got salt water and it's what we say unsaturated so there's no salt sitting on the bottom or anything like that it's all dissolved that would be an example of a homogeneous mixture however if you go past the saturation point and keep adding more salt all that could be dissolved in the water has been then when you keep pouring more in it actually will just sit on the bottom this happens with sugar as well and if you uh if you eat cinnamon toast crunch you know this so when you get to the bottom of bowl of cinnamon toast crunch there's just sugar crystals all over the place that would be another example sugar mixed with milk uh and not dissolved completely of another heterogeneous mixture so the same thing could happen in salt water if you've got some salt on the bottom so if you've added so much salt that you still got some crystals sitting on the bottom that is now an example of a heterogeneous mixture because you've got a certain amount of salt in the composition of the liquid part and then you've got a greater amount of salt down below and so you don't have a uniform composition again good example of a heterogeneous mixture all right the last little bit of vocab here is intensive versus extensive and these are descriptors of properties you can have an intensive property or an extensive property for matter so and it really all comes down as does the size of the sample of whatever substance you have does it matter does the size of the sample matter so if the size of the sample doesn't matter then it's an intensive property so however if the sample size totally matters that's going to be an extensive property and so hopefully this uh uh i shouldn't say hopefully but this probably seems a little bit vague right now but we'll definitely make this concrete and so a good example of an extensive property might be something like mass and so let's say i've got like a glass of water versus a whole swimming pool full of water um well one of them is going to be far heavier than the other the swimming pool full of water and will definitely have a greater mass and so the size of your sample totally affects mass mass is an example of an extensive property so lining up right up with that would be volume and volume is pretty much how much space a substance occupies or your sample occupies and again the swimming pool full of water has a much greater volume than the glass full of water and so volume is totally again another example of an extensive property now intensive property again is a property that the sample size itself does not matter and a good example of this would be melting point and so the melting point of a substance the just the temperature where it undergoes the phase change from solid to liquid and for water this occurs at zero degrees celsius or 32 degrees fahrenheit but we'll use celsius a lot more commonly in this class so zero degrees celsius that is the melting point and it turns out it doesn't matter if you have a glass full of water or a whole swimming pool full of water it's gonna undergoes that phase change from solid to liquid at 0 degrees celsius and so any of your phase change temperatures those are good examples of intensive properties so but i want to put one other on here that commonly shows up in this context and that's density we'll study density a little in a little more detail here in the next chapter but technically density is simply the ratio of mass to volume for a substance so it turns like if you have water it turns out that one milliliter of water weighs one gram and so we'd say it has a density of one gram per milliliter and those units shouldn't make a whole lot of sense now but it turns out that it doesn't matter if you have a glass of water or a swimming pool full of water its density would be one gram per milliliter in either case and this is not very intuitive here because mass by itself is an extensive property the size of your sample affects the mass so volume is an extensive property the size of your sample affects the volume but when you take the ratio of mass to volume that is not affected by the size of your sample so again that's not intuitive and you definitely want to file away that density is an example of an intensive property so often on an exam here you're going to get questions that involve identifying whether a property is intensive or extensive as well as possibly just simply knowing the definitions and density is one that shows up really commonly because it's not intuitive so one thing you'll find out about chemistry teachers is they'll tell you that they're not trying to ask you trick questions on a test and they're lying to you just so you know uh and so as a common question they'll throw density on there because it is a little bit tricky because mass and volume individually are both extensive but the ratio of mass to volume density is totally intensive cool and this is the last little bit of the vocab in this chapter for the descriptors of matter so hopefully this lesson on matter at least makes a little bit of sense uh but you'll find out that you need to reinforce it with some practice so whether you've got a good textbook or something like that or you can check out my premium course on chadsprep.com plenty of practice materials in there but you definitely want to reinforce this with some practice you'll find that chemistry is a lot like a math class where the real learning doesn't come when you like read a textbook or even watch a good lecture or anything like that the real learning is going to come when you do some practice