 All right, we have been joined for this next section by this young lad here. This guy, I'm gonna have to read his name to you because I can't remember all five of his names. I only remember his very last one. You will remember his last one too, perhaps? His name, he's an Italian scientist. He died in 1856 and his name is Lorenzo Romano. Amadeo Carlo Avogadro. He's gonna hang out with us. I'm not gonna tell you why he's here just yet, but I wanna talk about solutions and he's going to help. Solutions are, I told you this already, but I'm gonna write it down this time. They're homogenous mixtures and they have a big part. I don't know how else to describe this. They're homogenous mixtures made up of solvents and solutes. And the solvent is the big part and in everything that we're gonna do in this class, guess what the solvent is? It's gonna be water. Where solutions can be made of things other than water. The solvent doesn't have to be water, but if you're just like, dude, waters the solvent, you'll be in good position. Solutes, on the other hand, are any particles that can dissolve in the solvent and mix equally, evenly through the whole thing. So solutes in our case, mostly are gonna be particles or ions or glucose or sodium. Like we're gonna be dealing with things that are relevant to living systems. Now, you can measure, this is the important piece here. You can measure the concentration. The concentration of a solution can always be calculated by looking somehow, looking at the number of particles in a solution over, so that's your solutes, over the volume of the solution or the solute. This is, I abbreviate the word solute. Solution with a little n, S-O-L, little n. So when you see that, I'm doing shorthand for solution. So we can always calculate the concentration of any solution by figuring out the number of particles and the volume. And do you agree that a more concentrated solution is gonna have more particles in a certain amount of volume and a less concentrated solution is gonna have fewer particles in that same amount of volume? It will not help us if we're not speaking the same language or using the same units when we calculate concentration. And in our class, the unit of concentration that we are going to use is molarity. Now, I feel like somewhere I have talked about the mole. The mole. So let's just do that right now. The mole. Have you heard of the mole? I wish I had a picture of a mole here to help us. We need a mole and we need senior Luis Amadeo, Carlo Avogadro, Lorenzo Romano, Amadeo. That's where he comes in. The mole is also known as Avogadro's number. He came up with this. The mole is a way of counting things. And it's 6.02 times 10 to the 23rd power. That's one mole of things. If you look at that and you're like, what even? Like what, what even is that? That is 602 sextillion things. Not a million, billion, trillion, quadrillion, quintillion, no sextillion. 602 sextillion things. That is an massive, incomprehensible number of things. A mole is like a dozen, except a mole is 602 sextillion things and a dozen is 12 things. You can decide, do you want a mole of donuts or do you want a dozen donuts? Who even asks a question like that? Take a mole, thank you very much, Mr. Avogadro. Okay, our mole of things. You might be like, on what planet are we actually counting a mole of donuts? Only in my world where I wish that I had them here to eat right now, to keep me going through this lecture. Most of us do not count to a mole, but a mole of hydrogen ions. Think about that for a minute. One mole, 602 sextillion hydrogen ions has a mass of about one paperclip. It gives you a sense of how tiny atoms are. They're just ridiculous because it takes 602 sextillion of them to even be as big as a paperclip. So this is just a massive number, but it's really helpful for calculating numbers of atoms. Now, the interesting thing is that if you have one mole, one mole of solute in one liter of solution, you have a one molar solution. So it becomes a measure of concentration. If you have two moles of solute in one liter of solution, then you have a two molar solution. I could say to you, okay, I have a 10 molar solution and I have a five molar solution. Which one's more concentrated? And you would say, home girl, it's a 10 molar solution is more concentrated because there are 10 moles of molecules in that one liter of solution instead of five moles of molecules. Calculating molarity is knowing the concentration of a solution is super important. And it's something that critters' cells need to maintain a certain concentration of their inner guts. And multicellular critters like us have to maintain a certain concentration of internal fluids like blood. So much so that we will drink water or pee if our concentration of our blood concentration, if our molarity of our blood gets out of whack. It's a highly controlled quality of critters. They need to take care of that stuff. Related to molarity and concentration is the idea of pH. So in this next section, we're gonna talk about acids and bases.