Aqueous solutions

- [Instructor] What we have here are drawings of five different glass beakers, each holding different liquids or combinations of liquids and other things. Now the first one here, I would just call that liquid water that's in this beaker. We're gonna assume everything here is a liquid. Now, this next one gets a little bit interesting. I have water, but inside of that water I have stirred in some sand. So we would definitely call this over here a mixture. We have mixed that sand into that water. Now, you'll sometimes hear the terms homogeneous and nonhomogeneous. And really homogeneous means that the concentration of whatever's mixed in is the same throughout. So maybe if that sand is mixed in really well and the concentration is uniform throughout, someone might call that a homogeneous mixture. But more likely, that sand is going to settle at the bottom of the container, if it's the sand that I'm familiar with. And then the concentration is clearly not the same throughout the water or throughout the volume of this mixture and then it would be a nonhomogeneous mixture. Now, in this next beaker, I'm not dealing with water anymore, but I'm still dealing with liquids. These are two different types of alcohols. We have mostly ethanol here and then we have a little bit of propanol. You don't have to know the difference between ethanol and propanol for this video, but you just need to know that those are two different types of alcohols and they've been mixed together really, really, really well. So in this one, the concentrations of the two are going to be not the same to each other, but the percent, if you took any amount of this mixture right over here, we were gonna find that it's 5% propanol and 95% ethanol. So it's uniform, relative concentrations throughout. So this one I definitely would call a homogeneous mixture. And when we're talking about a homogeneous mixture where you can't filter out, say the propanol here, we would call this a solution. And when you're dealing with a solution, generally speaking, you have the thing that you have a smaller amount of being dissolved and the thing that you have a larger amount of. And so the thing that we are dissolving, generally speaking, the smaller amount of, this is called the solute. And the thing that we have the larger amount of, in this case, the ethanol, we would call that the solvent. The solute is dissolved inside of that solvent. So this right over here is a solution. Now, next over here, we're back to having water. And now inside that water we have dissolved sodium chloride, which is table salt. And sodium chloride, when you dissolve it, let me show the sodium. It dissolves into sodium positive ions and chloride negative ions. Let me do it in a different color. Chloride negative ions, obviously they're nowhere near this big and we're talking about a much larger number than I'm showing right over here. So this is also a solution. You're going to have the same concentration of the sodiums and the chlorides throughout, assuming that it is mixed in well. So this once again is a solution. Pause this video, what is the solute here? And what is the solvent? Well, the solvent is what we have more of, so this is a solution where the solvent... I know these arrows are getting a little complicated. The solvent is water and the solute over here is the sodium chloride. Or we could think of it as the sodium positive ions and then the chloride negative ions right over there. And this solution in particular, which is salt water, what's interesting about it is, it's dissolved what's known as an electrolyte. Sodium and chloride, this is an electrolyte. And when it's dissolved, then you have these positive ions here, which can move around. And so this is actually really good at conducting electricity. Now there's also another word when we talk about a solution where water is the solvent. We call this an aqueous solution. And let me just write that in blue 'cause that feels appropriate. Aqueous, aqueous solution. And sometimes you'll see that abbreviated as aq, which is going on right over here. Now last but not least, I have glucose mixed in with water. Now this again, is going to be a solution, And not just any solution, it is an aqueous solution because the solvent is water. Now the solute in this case right over here, glucose, it's a molecule that won't disassociate into negative and positive ions, but it does have parts of the molecule that are polar, and that's what makes it good for dissolving in water, so it will dissolve well in water. But this one is nowhere near as good at the salt water at conducting electricity, but it is an aqueous solution. Now, the last set of words, I'll tell you, because we might as well while we're talking about this. And there's no hard cutoff here, but if I have a lot of solute here, we tend to say that it is concentrated and if we have very little solute here, we tend to say that it is dilute. So I will leave you there. I've just thrown a lot of terminology at you, but that hopefully this helps you understand some of these terms like solutions, homogeneous mixtures, and aqueous solutions a little bit better.