introduction to chemistry matter and the elements okay so let's do a quick little introduction to chemistry and matter so basically chemistry is the study of the interaction of matter and energy and generally matter is considered to be a substance consisting of atoms now this isn't strictly true but we can borrow this definition for right now this is more of a historical definition what we are going to concentrate on is the classifications of matter in this course so how do scientists think about matter well matter is systematically ordered into two categories mixtures versus pure substances and then we can take each one of those categories and break them down even further so for instance we can take pure substances and we can break it down into elements versus compounds we can take mixtures and we can break it down into heterogeneous mixtures versus homogeneous mixtures and then we can also take pure substances and break them down into the phases of matter okay so pure substances so let's talk about elements and compounds first and the differences between those so basically if something is a pure substance that means it has distinct characteristics and every single sample of it has those characteristics and pure substances can be elements or compounds so this is really important so it doesn't have to be a Pure Element to be a pure substance it can be a compound and be a pure substance now elements are composed of only one type of atom okay one type and they're all found on the periodic table so if you look at the periodic table everything on there is an element and atoms are the smallest chemically distinct form of matter okay and so we're going to discuss atoms in Greater detail later in the course we'll come back to that but elements are all found on the periodic table so some examples of elements gold that's Au on the periodic table oxygen gas now notice that's not just one atom of oxygen that's two O2 means two atoms of oxygen bonded together for oxygen gas liquid nitrogen which also comes as a datomic molecule in the elemental form and helium which is H okay so we can as I said we can take a compound and that can be a pure substance as well and this is when we have more than one type of element or atom bonded together so for instance water has two hydrogens and an oxygen bonded together and water is a pure substance okay so compounds have different types of atoms present in fixed proportions so if you take one sample of water it's going to have two hydrogens and an oxygen bonded if you have take another sample it's also going to have two hydrogens and an oxygen bonded and compounds have properties that are very distinct or different from the elements from which they are formed so in other words when you create a compound by chemically bonding different elements together you create a whole new substance and so there are tons and tons and tons of compounds and these are also called chemicals but in chemistry we're going to call them compounds generally um one of them is sucrose so that's just table sugar okay so we have 12 carbons bonded so there's the 12 carbons we have 22 hydrogens and 11 oxygens all bonded together and that's going to give us a sucrose molecule so sorry this should say sucrose not glucose okay other everyday examples of compounds are things like table salt so we're going to make friends with this throughout the course so this is sodium chloride a sodium cation a chloride annion bonded together ionic bonding that's table salt it's a pure substance and also water as I mentioned previously H2O okay so now let's talk about mixtures versus pure substances so how can you tell the difference all right so when you put two or more pure substances together then you're going to get a mixture okay and each substance in the mixture retains its original characteristics so for in other words it it is still chemically distinct okay so you can mix them together but each substance retains its chemical nature or its distinct characteristics and so when you make a mixture you don't create a whole new substance and you can separate mixtures using various physical separation methods for instance examples of mixtures include syrup and so that's s uh sucrose in water all right so let's say we were to evaporate off all the water we would be left with the sucrose in there and then whatever else is in your syrup um air is another mixture okay and that's mainly nitrogen and oxygen and a few other gases like argon small amounts of other gases that's a mixture okay milk milk is a mixture okay and also cucumber onion and tomato salad is a rather obvious mixture okay so now let's just look at mixtures now there's two types of mixtures heterogeneous and and homogeneous okay so now a homo homogeneous mixture is uniform throughout so like if you were to look at a homogeneous mixture and you kind of you know look over the whole sample you can't visually separate the components okay so for instance if you have homogenized milk so if you you that's a mixture sitting in your fridge but it's been homogenized which means that it's basically been treated so that the cream and the water phase don't separate from each other so that's homogenized milk that's where it gets its name orange juice you know without pulp that's another homogeneous mix mixture brewed coffee and blood so those are all homogeneous mixtures uniform throughout a heterogeneous mixture is one in which the components do not appear uniform so for instance if you take fresh milk so if you milk the cow and let the milk sit there you're going to have cream floating on the top so that would be an example of a heterogeneous mixture another heterogeneous mixture is chicken noodle soup okay okay so we have the broth and then we have the noodles and some pieces of chicken and perhaps some carrots whatever else you want to put in there another heterogeneous mixture is a nut mixture so you can see the individual types of nuts in there and then also something like orange juice with extra pulp which I do like all right so now phases of matter okay so we have three main categories there are two others but we're mostly going to deal with the basics right now and so those are gases liquids and solids which you're probably already familiar with and each phase has its own characteristic properties so this is how they're defined so gases have no definite shape so when you put a gas in a container it's just going to take the shape of the container they also don't have a specific volume so if you put a gas in a container it's going to fill the whole volume also and so some examples of gases are steam so that's water vapor in air okay and oxygen gas okay so liquids now liquids don't have a definite shape so that means when you pour a liquid into a container it's going to take the shape of the container so if you pour a glass of water the water is going to fill the shape of the container that you put it in but they do have a specific volume so let's say that you put in one cup of water into a fourq container that is not going to you know fill up the whole four quarts it's only going to fill up the one cup of water that you put in there and some examples of liquids water obviously gasoline olive oil and vinegar we're going to learn more about liquids later on in the course as well as gases and then finally solids these guys have a defined shape and volume and examples include ice salt wood and granite so basically the these are your I mean we're all familiar with solids so if you take liquid water and you freeze it you get ice which is a solid okay so here's a little bit of practice so identify each substance as an element or a compound so we're only going to deal with element versus compound right now so pause the presentation and give it a shot all right sodium chloride so this is a compound because two types of atoms are bonded together okay so we have sodium atoms and chlorine atoms but of course these are ions we're going to find that out so sodium plus chloride minus sodium chloride held together with electrostatic attractions but this is a compound because it has two types of atoms bonded together with ionic bonds Neon gas now this guy is an element because there's only one type of element present in the substance so we can just look on the periodic table and we see Neon liquid mercury same same situation basically an element because there's only one type of element present in the substance so if you look on the periodic table you're going to see HG for Mercury right there in the transition metal section alumina all right now this is a compound because it has two different kinds of atoms bonded together so it has aluminum and oxygen and every sample of alumina is going to have two aluminum for every three oxy and then finally iodine crystals now this is an element and it's kind of tricky but it's an element because there's only one type of element present in the substance so we have two iodine atoms bonded together to form iodine this is how iodine exists naturally so in its Elemental form it's it's a diatomic molecule okay so now let's practice identifying substances versus mixtures so go ahead and try those and then pause the presentation and then we'll go through them okay so the first one sodium chloride okay every chemical compound is a pure substance so this guy is a pure substance all right so you might be tempted to say mixture because you see two different things in there but those are chemically bonded together so that means it's a compound and chemical compounds are pure substances all right diamond so this is a bunch of carbon atoms coal bonded together and diamond is one elemental form of carbon there are others like graphite but diamond is an element okay cotage cheese so this is a mixture of cheese curds and whey so that's a mixture not a pure substance iron metal elements are always pure substances soil are basically dirt it's a mixture of Min minerals and organic matter and whatever else happens to be in there so that is a mixture and then finally a casserole there are lots and lots of different kinds of casseroles but there's always some sort of mixture going on so you can have potatoes chicken peas gravy whatever you want in there okay so now for our last little mini quiz let's identify each mixture so we know they're all mixtures as heterogeneous or homogeneous so go ahead and pause the presentation and give it a shot okay sodium chloride and water all right well that is a homogeneous mixture so you cannot separate the individual components visually they can't be observed separately we're also going to find out this is a solution all right veins of gold in rock okay so that's a heterogeneous mixture so you see rock you see the mineral The Rock and then you see veins of gold kind of streaking through that so that's a heterogeneous mixture and you notice that they're both solids so you can have mixtures of solids in other solids okay a casserole is a heterogeneous mixture so it's a mixture and you can visually separate the components it won't be uniform throughout so that's a heterogeneous mixture soapy water is a homogeneous mixture uniform throughout and then water with ice cubes is a heterogeneous mixture of phases so it's all water but it's a heterogeneous mixture of two different phases solid and liquid