 Today I'd like to talk to you about solutions, particularly as solutions relate to electrolytes. And as we do this, let's just review a little bit about what we have when we have a solution. Solutions are homogeneous mixtures of two or more substances. When we have a solution, we typically will have a solute and a solvent. There can be more than one solute in a solution. The solution is defined as that which is present in greater quantity. It dissolves solutes. Solutes are dissolved, they're present in lesser quantity. So literally what we're talking about here then if we skip down here to concentration, concentration is the amount of solute that's in a given amount of solvent. It can also be expressed as the amount of solute that's in a given amount of solution. So in doing that, we basically have defined and reviewed what we need to review. Let's talk about electrolytes for just a second. Electrolites are a topic that we hear a lot about because electrolytes are items that we need in our body. There are producers of sports drinks and other types of drinks that will essentially replace the salt solutions, the electrolytes that our body loses during the day whether we're exercising or just walking around. These electrolytes are important because they actually allow our body to conduct business the way it's supposed to. Electrolites by definition are going to be conductors of electricity. They are essentially solutions which have ions in them. Our bodies are filled with these. If we do not have enough ions, we can't get the flow of electrons through our body as we need and it can result in actual death if we don't correct that. If we look at these two equations, I have listed here sodium chloride which is salt When sodium chloride is dissolved in water, it forms sodium ion and the chloride ion and you have your water. These are solutions that are essentially what we call strong electrolytes. These electrolytes are completely dissociated in the solution. If you put a meter in the solution, you would find that there would be conduction of electricity through that solution. There's also a really neat experiment where you put essentially a light bulb in and you can see how the solution conducts the electric current and allows the bulb to light. If you do the same thing for sugar and you dissolve a certain amount of sugar in water, what you find is that the sugar becomes liquid. It mixes with the water. It dissolves but the sugar does not ionize. So the sugar solution will not conduct electricity. If you do the same test with the sugar solution that you did with the salt solution, the light bulb will not light up because there's no electrons flow within that solution. You have to have an electrolyte to do that. As I mentioned earlier, this is a strong electrolyte. Strong electrolytes are completely dissociated. There is such a thing as a weak electrolyte. Essentially what happens there is that in a solution of water, the acid will dissociate into ions but it will never completely dissociate because as these ions form, they tend to recombine and form the reactant again or the acid again. In instances where you were comparing the two solutions, this solution which was a strong electrolyte and this solution which was a weak electrolyte, if you were using a light bulb test, you would find that the light bulb would be much brighter here because you have more stable ions than it would here. When we talk about concentration in solutions, we're primarily or at least if not primarily a good bit of the time, we're talking about molarity. And molarity is defined with a capital M or it symbols a capital M. It is defined as moles of solute per liter of solution. Moles of solute per liter of solution. Now a lot of people are mixed on this but I love these triangles because the triangles are so useful in teaching this concept. They work this way. If you cover up molarity, you can see that molarity is defined by moles over liters. If you wanted to calculate the number of moles that are in a solution, if you cover up moles, essentially what it's telling you to do is to multiply molarity times liters. And if we were interested in the volume, you would cover up volume and you would determine that molarity divided, I'm sorry, moles divided by molarity would give you your volume. Three reactions or three mathematical manipulations you can do using this. For people who are good with mathematics, good with algebra, all you need is that molarity is equal to moles over liters and you can manipulate that to solve for whatever you need. So that's certainly an important thing. Now suppose you have a solution and that solution has a concentration which is not what you need and you add solvent to that concentration. The question is, what have you done to that solution? Think about it another way. Suppose you have Kool-Aid that has too much sugar in it, what are you going to do? Well most people if you had a little bit more Kool-Aid mix would add more Kool-Aid mix and then dilute the sugar with solvent which is water. In chemistry we do pretty much the same thing. When we do it, it's called dilution and the equation listed here M1B1 equals M2V2 is known as the dilution equation and this equation is used only in instances where you are diluting a material into something that is more dilute but you can also use it in another direction to determine the amount of concentrated solution that is needed to form a large quantity of diluted solution. So what if I told you that you have two liters of solution that has one mole of sodium chloride and I ask you to determine the molarity. Looking at our molarity triangle if we cover up molarity it tells us to divide moles by volume. In this case we have the one mole of NaCl divided by two liters of solution and we find out that the molarity would be 0.5M which is basically 0.5 molar. So that would be an example of a calculation done from the triangle. Okay suppose we took this 0.5 molar solution in NaCl and that we originally had two liters of solution and we actually added another liter of solvent so that we would now have three liters. What would our concentration be of the new solution? We can calculate this using our dilution equation. This is going to be our first molarity M1. This will be our first volume. That's where we start it. When we dilute it our new volume by adding one liter of solvent will give us the second volume of three liters. So the question becomes what would our second molarity be? If we manipulate the equation we find that M2 would equal the molarity of the first volume and that's molar over two times two liters divided by the final volume which is three liters. And when we do that we find that the new molarity M2 is 0.33 molar. Now I want you to be sure that you understand this. The original solution that we had, the original solution that we had contained one mole of the sodium chloride. Diluting it to three liters did not change the quantity of the original solvent. We still have one mole of that solute. We have one mole of the solute, sodium chloride. We have increased the volume and so the concentration of that material is less meaning that it's gone from a half molar to 0.33 molar. Let's finish up with the discussion of solution properties. Let's talk a little bit about these. Solution properties are sometimes called colligative properties and what that means is that the amount of solute in a solution will change the properties of that solution. Now we all know that water freezes at zero degrees Celsius. We know that water boils at 100 degrees Celsius. So why is it in the winter time that engine blocks don't freeze up in Minnesota when the temperatures are well below freezing? The answer is antifreeze. Antifreeze. And antifreeze is added to water and it lowers the freezing point of the water below where the freezing point would be during the winter so that your water in your radiator doesn't freeze and your car doesn't get messed up from that. Causeless, think about it. Water when it freezes expands. When it expands it can break things, i.e. it doesn't do well in your car. When it's that cold. You can do the same thing with water if you add salt to it. Adding salt to water, adding salt to ice when you're making a homemade ice cream lowers the freezing point of that mixture so that you can freeze your ice cream. While adding a solute to a solution will lower its melting point or freezing point, adding that same solute will also elevate the boiling point. Let's think about this. If you're out in New Mexico and Texas during the summer or other areas where it's very hot. Your car has to really work hard to keep itself cold. Think about it. Water boils at 100 degrees Celsius, 212 Fahrenheit. The temperatures inside an automobile engine are much higher than that. So why doesn't your water all evaporate? Well, it's under pressure, yes, but the antifreeze not only will decrease the freezing point, it will also elevate the boiling point so that you don't have boil over quite as much as you would in other situations if it was not there. There are people and companies that have made their fortunes selling these kind of things to consumers and it's a good thing. Now, aside from this, what other things, well, if you are familiar with viscosity which has to do with the thickness or the resistance of flow to a material, viscosity can also be changed by adding a little bit of solute to it as can osmotic pressure. So we have this morning talked a little bit about solutions. We've talked about electrolytes. We've talked about solution properties and I hope that this will benefit you as you move through your daily life.