Full transcript
0:00Robin Reaction dot com
0:02In this video, I'll be going over the differences between pure substances and mixtures
0:07And so first we're going to go over some definitions and this chart on the left and then we're going to do practice problems
0:14So let's start off with the very top of this chart which is just all matter. So matter is basically what the entire
0:22universe and earth and everything you're going to see in your life is made of
0:26There are some exceptions some things that you're going to see are made of energy. That's mostly light or heat. However,
0:33Things that you think of as things you can pick up and carry all of that's made of matter
0:39and so within that matter we have our first two categories which are pure substances and
0:45mixtures and so now we have to start getting into
0:49Actual atoms and molecules to understand the differences between pure substances and mixtures
0:55So the very first thing we're going to look at is
0:58Elements and so elements are just what's on the periodic table. There's a limited number of them
1:04You can look them all up just by looking at the periodic table and what that means that you have one
1:09Type of atom and so you don't have any bonding of different atoms to each other
1:16You don't have any more complicated molecules. You don't have more than one type of atom
1:22You have one single type of atom on the periodic table
1:26and so that's one type of purist substances and the other type is just a compound and
1:32So in this sense compound really means molecule what it means is that you have a chemical bond
1:40Usually it's going to be a ionic metallic or covalent that's making multiple atoms come together
1:47to form a molecule
1:49So in this case, you could think about it in terms of h2o so you could say okay
1:54The blue is actually going to be the oxygen in this case
1:59and then each purple is a hydrogen that the water is bonded to
2:03So those are our two types of pure substances
2:06And the main thing we can just see is that there's only one
2:09Type of thing right either you have one type of atom or you have one hypo molecule
2:14So in our example for a compound every single one of these molecules is an h2o molecule
2:20We don't have a secret salt molecule hiding in there. We don't have a secret other type of element hiding in there
2:28So if we had all these h2o molecules and then we had one atom of just oxygen by itself
2:34That still wouldn't be a pure compound because we wouldn't have the same type of molecule for every single thing
2:39All right. So now just to get into this definition pure substances one type of atom or molecule
2:45It's all the same thing and it has unique physical properties
2:49So what the physical properties means are things like?
2:53What temperature they boil at or what temperature the freeze at or their density?
2:58and so your teacher may go over another list of physical properties that pure substances all
3:04Have but basically it's just kind of a definition thing where these pure substances have certain things
3:10You can look up in a textbook and say hey, we know that water always boils at a hundred degrees Celsius
3:16That's just a fact about water. So now we're going to go over to mixtures
3:21So these mixtures come in two types?
3:25Homogeneous and heterogeneous, and so we can see just from these little pictures
3:30What's going on and the differences between them? So homogeneous our first one is where everything is?
3:37completely mixed together evenly we can see already as opposed to our pure substances where we just had either red dots or
3:45Blue and purple molecules now in the mixture we have an orange and we have a green now
3:51It doesn't matter what these things are. These could be atoms
3:54These could be molecules what's important is that they're completely evenly spread around
3:59so if you were to look in here and try to say oh
4:02Is there an area with more orange or with more green the answer would be?
4:07Not really and if you averaged out all of the areas, it's pretty much going to be completely blended now
4:13Yeah, we could go like this and say oh this square just has greens
4:16But really when we look at the whole thing, we can just kind of visually see it's blended together
4:21That's not really separated versus heterogeneous
4:25So in heterogeneous, the May thing is that we have two or more things
4:30But they're physically separated
4:33So if we were looking at this we could say oh, yeah
4:37There's this clear area where we have this one type of molecule and then we have this one type of atom
4:43Down here. We can clearly see there's a division. And so the definition for all mixtures are a
4:50Random blend of two or more substances. Both of these examples have two things in them. You could easily have more right?
4:57It's not a mixture. It's not like it's not a mixture if you mix five things together, that's still a mixture
5:02It's just at least two and then it has no unique physical properties and what I'm talking about
5:08There is the same things that we were doing for pure substances
5:11so basically if we're saying
5:14We're saying that these mixtures don't all have the same density or don't all have the same boiling point or melting point
5:21It's going to depend on what the mixture is made of and then another thing for this is that we could have a mixture
5:27That's 50/50 we could have make sure that's 60/40 90/10 so it can't have these unique physical properties because there could be many different
5:35variations of that mixture
5:37Alright, and then the last one is that it can be physically separated
5:41and so what that means is that with mixtures you can do things like you can filter them out if you had a mixture of
5:49Sand and water all mixed together
5:51You could just filter that and you can do other type of lab techniques where you can actually separate these things
5:58Where it whereas with pure substances, you can't really do that
6:02You can't separate water from water in a meaningful way you can cut it in half, but that's not like a separation technique
6:09right If you are going to break apart a pure substance
6:12You're gonna have to actually do chemistry and break and form these bonds that keep these things together. So
6:20Overall that's our definition and now let's go ahead and just get into practice problems. All right, so here are six different things
6:27We're gonna break down if they're pure substances or mixtures and then even farther into what type of these things they are
6:33So starting with aluminum foil if we check the periodic table
6:37We will see aluminum there and there's actually nothing else aluminum foil is made of it's just pure aluminum
6:44And so that means that it's a pure substance and then even further than that
6:49We're going to say it's an element. All right, and next let's do air ignore the balloons in the clouds
6:55This problem is just talking about what air is and so air is not 100 percent oxygen which is what we breathe includes
7:03Nitrogen and several other gases and so this is definitely going to be a mixture
7:09But when you think about breathing, it's not like sometimes you take a breath and oh
7:13I got a ton of oxygen in that breath and sometimes you take a breath and you didn't get any oxygen
7:19Right, it generally feels about the same each time
7:22And so that's because the air particles are completely mixed around evenly and so we'd say that this is a homogeneous mixture
7:30All right, next we're talking about dirt. So we look on the periodic table
7:34there is no dirt element and
7:37If we kind of stare at dirt, we can see it's not exactly one thing if you're staring at dirt
7:42There's gonna be little hard pockets little darker and lighter spots. And so we know it's gonna be a mixture dirts
7:49definitely not just one type of molecule or
7:52Element and also it's going to be a heterogeneous mixture. It's not completely evenly broken down there are places where you can clearly see
8:00Ok, there's different things going on here than there are here so next water
8:06This is our example from earlier again. Ignore the air bubbles in this picture. We're just talking about water
8:12So water is made of h2o
8:15Every molecule of water that exists is made of h2o. There is no other version of water
8:22So we'd say this is a pure substance and we'd also say it's a compound
8:27There's no water element on the periodic table
8:30All right. So next we have steel so we look at that and there is no element called steel and
8:37You wouldn't necessarily know if it's a compound or not until you knew a little bit more about how you make steel
8:43But it's actually a bunch of different metals melted together and the form steel overall
8:49so steel is definitely a mixture and
8:52It's a homogeneous one right when you look a piece of steel
8:55it looks like a piece of steel not a ton of differences between
8:59two or three inches down on a chain-link or a plate of steel and
9:04Last we have pizza. And so this one is pretty clear. Right? It's definitely not an element. That'd be cool, though
9:10It's not a compound. It's definitely a mixture and
9:14It's going to be heterogeneous, right? We can clearly see that different spots exist. It's not all the same consistency
9:21All right. I hope this video cleared up the differences between pure substances and mixtures for you
9:26Hey, I hope you liked that video
9:29Please feel free to like comment or subscribe and if you go to my website
9:33I have a ton of free practice problems. You can check out if you need even more help
9:36You can hire me for one on one private tutoring sessions that are online. All right. Thanks. That's it. Happy studying