Now we're going to have a couple different sets of units of concentration and we're going to define concentration as a quantitative measure. Quantitative means with numbers. Whereas qualitative means without numbers generally or without specific detailed numbers. So quantitative measure of the amount of solute in a given amount of solvents. And we have a set of units for this. The units are called malarity. Those are the same chemistry units that you're going to be talking about quite a bit now and in future chemistry courses. And the abbreviation for malarity is capital M. And it stands for moles of solute per one liter of solution. And as we'll see, I will usually do something like this, blank M, which is from malarity. And in this case, we'll be talking about sodium chloride. So I'll do blank malarity sodium chloride. Because the malarity tells you what units it is for the concentration. And the sodium chloride tells you what your solute is. And whenever you have a solute dissolved in a solution, you'll need both of those parts. And then it'll be blank moles of NACL over blank leaders of solution. And oftentimes problems, as we'll see, will give you two of these three numbers. These blanks are for numbers. And you'll have to find the third. Now, before we do some problems, though, I want to talk about how to make a solution. And hopefully you can see this. So we've got a volumetric flask here. And a volumetric flask is the best way to make a quantitative concentration of solution. And here we've got a way out and add 1.00 moles of sodium chloride. We can calculate that as 58.44 grams of sodium chloride. And we're adding that here into the volumetric flask. And then it's a little hard to see. But you're adding the water up to about here. And you're dissolving. So you're going to shake it around to or swirl it, usually actually swirl it to dissolve all the sodium chloride. And the reason we do this, so we fill it up only partially is because sometimes when the solid or whatever it is that we're dissolving dissolves, it changes the volume. So a good practice is to always dissolve it before filling to the total volume. And what I mean by the total volume is inside this, you're going to add water until solid is dissolved and add additional water until the one later mark is reached. And so the one later mark on this volumetric flask is always on what's called the neck of the flask. And the neck of the flask is this portion here. And the line is right here. So initially you fill it to here, then dissolve, then you're going to fill it up to exactly the line. And that is hard to see. But the solution is filled up to exactly this line. It's then mixed again to make sure that all of this is uniform and how motinious. And you get, let's see, so you have 58.44 grams, which we're converting to moles, we have 1.00 moles of sodium correct. And we're going to put it in exactly 1.00 liters. And 1 divided by 1 creates a 1.00 molarity. And solution of sodium chloride. And sometimes we are a cute nickname for molarity is molar. And so one way of pronouncing this is, well, we can just say 1.00 molarity sodium chloride. And go ahead and write that down here. And then you can also say 1.00 molar sodium chloride and write that down here as well. Those are the pronunciations of this set of units.