Video transcript
- [Instructor] I suspect thatyou might already be familiar with the term mixture. It really does meanwhat you think it means. If you take two or more substances and you were to mix them together, you are dealing with a mixture. And it could be a solid,a liquid or a gas. Now there's fundamentally twodifferent types of mixtures. There's heterogeneous mixtures. And hetero, you're goingto see that prefix a lot, means different. So heterogeneous, thisis referring to mixtures that if you look at itfrom a macro point of view, I'll do a heterogeneous liquid mixture. And what I often think ofhere at the extreme form is where with my naked eye, I could see that differentparts of the mixtures have different concentrationsof the different things that have been mixed up. One example I often thinkof is chocolate milk that's not well mixed. At the top you're goingto see these clumps and depending where you are in the milk, you can actually see it with your eye, that you don't haveconsistent concentrations of the different substances. The properties of themixtures are different, depending on what part ofthe mixture you look at. Now, you can imagine ifthere's heterogeneous mixtures, the opposite would behom*ogeneous mixtures. Those would be mixturesthat when you look at it from a macro point ofview, it looks consistent any point of the mixture. hom*ogeneous mixtures. And hom*ogeneous mixtures,there's another term for it, which you have probably heard. They're also known as solutions. And as I mentioned, whenwe talk about mixtures, we could be talking aboutsolid, liquid or gas. Oftentimes in our head, wethink liquid immediately, but it can be solid liquid or gas. And so the same thingis true for solutions. You can have solid liquids or gases. And an example of asolid solution would be, say a metal alloy. Where at the macro level it's color, how well does it conduct electricity? How malleable is it? How hard is it? It looks like the properties are uniform throughout the alloy. If I have some type of metal alloy, if I were to just look at it like this, if I were to look at say bronze, well, from my point of view, it has the same propertiesthroughout the bronze. And I should probably dobronze in a more bronze color right over here. But if you were to look at it with a very sensitive microscope or based on the models that we now know what isgoing on in that metal, in that alloy, what's happening is you actuallyhave a mixture of metals. But it is a hom*ogeneous mixture of metals because at a macro level, you can't really see the differences. Now at a micro level, you can, because there are differentmetals mixed in together in this alloy. Now, as can imagine youalso have liquid solutions and in chemistry, these are the ones thatwe'll often deal most. We will also deal with solidand gas solutions as well. And when I think of ahom*ogeneous liquid mixture or a liquid solution, the onethat comes to mind for me, but we'll see a lot of these in our journey throughchemistry is salt water. Salt water. Salt water has sodiumchloride dissolved in water. And if you were to go to the ocean, and if you were to justlook at the salt water, or if you were to measure itsproperties, even in a lab, you would see that the propertiesthroughout the salt water seem to be uniform. At a macro level, itappears to be hom*ogeneous. It appears to be uniform. But if you were to lookat what's happening at an atomic level, you would see that youhave your water molecules. Let me draw the water like that. That is the oxygen, eachof them has two hydrogens. And this end is partially positive, we've seen this multipletimes, the hydrogen end, the oxygen end is partially negative. And so when you dissolvethe sodium chloride, the chloride anions are attracted to thepositive ends of the water. So maybe you have a chloride anion there. And the sodium ions would be attracted to thenegative end of the H2O. So that's the sodium right over there. So when you look at itat a micro perspective, you see that there aredifferent molecules, but at a macro perspective,the macro properties, how it responds to different stimulus, how well it conducts electricity,what it even looks like, it seems to be uniform. Now to be clear, saltwater isnot the only liquid solution. There's many types of liquid solutions. In chemistry, we'll often see water as our most common solvent. That's the thing thatyou have the most of, the thing that other thingsare getting dissolved in it. The things that are getting dissolved are called the solute, in this case it wouldbe the sodium chloride and the water is the solvent. Let me write that down, solvent. When you have a solution where you have somethingdissolved in water, this is often called anaqueous, aqueous solution. And sometimes it's abbreviated aq. Now, last but not least, wehaven't talked about gases yet. And you can for surehave a solution of gas. And the one that's most common is the one that you and Iare breathing right now. The air around you is a gas solution. It's macroscopicproperties seem consistent, they seem uniform, but we know that the gas aroundus is a mixture of nitrogen, of oxygen, of carbon dioxide, as well as molecules of other things. So a good example of agas solution would be air. So I'll let you go there. That's just a good primeron what a mixture is, the types of mixtures and especially the subtype of a mixture, which is a hom*ogeneous mixture, which we often call a solution.
