 Okay, welcome to another smart board video presentation. And today's topic is going to be solutions and delusions. And these are two separate topics, but they're really related to each other. And so actually I think what I'm going to do is actually divide this up into two videos. This first one will talk about how they're related and actually get into some detail about delusions and then I think I'll make another video specifically about the solutions parts rather than make one long video, I think I'll divide it into two. The topic of solutions and delusions in basic lab techniques course is actually a very key skill. I mean you're very early in your careers and we present a lot of information in this course and I'm sure you're trying to sort out all these things, but this is a foundational skill. This is a skill that when our students go on their internships or we have our advisory boards, you know, making solutions and preparing delusions are kind of a skill that if you're a research technician this is what you're going to be doing. So it's key that you get a good understanding of this. So make sure as you go through this, don't just quiz through it, make sure that at the end of the day and particularly at the end of the course that you feel comfortable with your understanding of what's going on with making up solutions and preparing delusions. So let's look at some definitions and the first one we'll put up here is concentration. And the concentration is notion that kind of ties the solutions and delusions together. So what are her definition of concentration in terms of a chemistry application? And the first one we're going to think it's the strength of a solution, right? And you know, in the everyday life we talk about, you know, how strong is the coffee, how strong is the tea, you know? So that's the notion that the more concentrated it is, the stronger it is. So a concentration is kind of a measure of the strength, but that's not a very mathematical definition. So we're going to say that it's the amount of solute dissolved in a given volume solvent. And here again the notion of solvent, you know, in most of the labs that we're doing in biological systems, that solvent is going to be water in our aqueous system, so it might well be, say, alcohol. We see a number of, say, solutions of ethanol and methanol where those are the solvent. But so it's the amount of the solute which is dissolved in a given volume of the solvent. So the more of the solute is dissolved in a given volume, then the higher the concentration would be. There are various ways that we write the concentration solutions. You know, you've been working problems that should have looked at. Probably the most used is being infamilarity. Another pretty common one would be what we call how much mass to volume. And so you might have something like milligrams per mil, right? So that would be mass to volume. You might have grams per liter, right? So that would tell you a type of concentration. Another thing we've looked at are percent, right? What's the percent concentration? And another one that's maybe not as frequently used, but you'll see, is the term X. So you might see a solution. This is a 50X solution. Or we'd say this is a 58 concentrate. So if you had a 50X solution, you would tend to dilute that one to 50, 50-fold of B down to 1X. Now the problem with the X thing is that has to be related to something. The molarity, the mass, the volume, and the percent are based on masses that are fine. You have something that's, where they tell you this is some X solution, somewhere you have to have a recipe or a reference to what the 1X is. When I bring that up, because it is something we'll see in some of the experiments you'll get in the program, you'll find some what we call stock solutions that are made at a higher concentration, would be used at so that we dilute them to the working strength. So there's that term dilution. We took a 50X solution and we did a dilution to bring it to working strength. So all these things related and they're tied together by the notion of concentration. So now, solution. What's going to be our definition of a solution? We're going to say that a solution is a homogeneous mixture of solute dissolved in a solvent. Notice that we said dissolved. This is like if you're dissolving sugar and water or salt and water, they're dissolving and you mix them and that becomes a homogeneous mixture. Now, this is different than related thing. Now I'm going to put this over here on the right because I want to mention it, but it's not really the topic of our discussion. It's a suspension. A suspension is a mixture where the solutes in this case would be dispersed in the solvent, per se. This would be, and it doesn't have to be liquid. Dust in the air is a suspension. When it rains and you see the gas can turn red because of the red clay that is suspended in the water. It's been, you know, the force of the current has suspended it from the bottom. If it were to become still again, then that clay would settle back out. So it's not dissolved in there. It's suspended. And so you've probably had medicines that said it was an oral suspension, right? And you're going to have to shake it before you use it because there's probably something in there that has settled to the bottom. It's not dissolved, but it's just suspended. So you're going to have to resuspend it to get it mixed before you take it. Otherwise, you would take the medicine off the top and not get the stuff that had settled to the bottom. So there are times in the lab when you make things that are suspension, but what we're going to be concentrating mostly are solutions. And our definition is there again, a homogeneous mixture of two or more solvents that are actually dissolved in the solvent. Okay, what about dilution? Our dilution or definition of dilution is going to be increasing the proportion of solvents to solute, thereby decreasing the concentration solute. Okay, let's look at what they said. Now, first of all, there we see that word concentration again. So we're going to say we're going to increase the proportion of the solvent to the solute. Okay, so what we're talking about that coffee that we made, we said we got it too strong, it was too concentrated. So what can we do? We add solvents, so we could add some water. So that would increase the proportion of the solvent water to the solute. And then thereby decreasing the concentration of solute per volume. Now, we added some volume, but the concentration per volume of the solute would decrease. So we diluted it out, right? In the case of the coffee, we added some water to dilute it. So we were decreasing the concentration by adding solvent. So that's a notion of dilution. So we're going to start our conversation about dilutions. And the information that I'm going to be talking about can be found in your referenced pages or in your Sidemen text. Are there some of this information that's on the dilutions lab that you're doing in the lab? So that information is kind of in that kind of preamble to that dilutions lab. And one of the difficulties in dilutions is in the way that they're presented in procedures that you're following. And there's a lot of different ways that people refer to the way they do dilutions. And so you have to be careful that you understand what they mean. And sometimes that's difficult unless you have the context that they're working from. So I said there in the lab, the first rule in making dilutions is to read the procedures carefully so that you understand what it's saying. I said, for example, if the instruction one mil diluted to 50 mils is not the same as one added to 50 mils. You know, one to 50 mils diluted to indicates that your final volume is going to be 50 mils. So essentially you're going to have one mil that you're going to have to add 49 mils to get it to 50 mils. Or if you said one mil added to 50 mils, you know, it's going to be one plus 50, it's going to give you 51 mils, right? So those are similar sounding things, but they're not, they don't mean the same thing. And so there are a variety of ways of people speak about it, and unfortunately these can be confusing.