 Now, we have our chemistry background. You know what atoms are, you know how chemical bonds are formed, we have the concept of energy in relationship to our atoms, and now we're going to talk about one special molecule and that is my friend, the water molecule. And I've already drawn you some pictures. I'm going to draw you another one. This is my oxygen that forms a chemical bond with a hydrogen, actually not just with one, with two hydrogen atoms. And just keep in mind that this is actually sharing electrons. Now, I drew this picture just like that on purpose. So tell me, why? What did I draw? What's weird about this chemical bond? Is anybody like, dude, this is not an example of a covalent bond? Why not? Who's hogging the electrons? Oxygen hogging the electrons again. And it hogs both sets of electrons. Now, think about this for a second. If oxygen is hogging the electrons, tell me about the charge of oxygen when compared to the entire water molecule. Do you agree that it's pulling the negative charges more closely to it? The oxygen has chemical properties that cause that to happen. It's stickier for those electrons. It hangs on to them tighter, it hogs the electrons, which means it has more electrons surrounding it, which means that it is kind of a partially negative side of the molecule. Do you agree with that? Do you agree that, look at my molecule of water, and we've got the hydrogens on one end and we've got the oxygen on the other. And the oxygen is hogging those electrons, which means that the hydrogen, they kind of lost their electrons. And so the hydrogen end of a water molecule is partially positive. And that gives you a characteristic of water that's crazy. It's polar. It's a polar molecule. There are other polar molecules in the universe. Water is not the only polar molecule, but water, because it is a polar molecule, that gives it some characteristics that are basically essential to life. If water was not a polar molecule, you wouldn't be here. That would make me very sad because I'm glad you're here. But I wouldn't be here either, so I couldn't be sad because I wouldn't be here. What would happen if I took another water molecule? Let's just throw another one out here just for the heck of it. H, H, uh-huh, oh, there's another water molecule. And go ahead and label your new water molecule with its partially positive side, which side was partially positive? Positive, negative. Do you see anything magical that's about to happen here? The magic is about to occur. What's true about positives and negatives? Hoink, hoink, hoink, hoink, hoink, hoink, hoink, hoink, hoink. Hoink, hoink, hoink, hoink, hoink, hoink, hoink, hoink, hoink. They like each other. Opposites really do attract at the molecular level. Awe, guess what? They form a flavor of bond, these chemical bonds, and they're a little bit sticky for each other. And if you have a whole pot full of water molecules, the partially positive end of one water molecule is going to stick to the partially negative end of the other one. Now, is this like a super, super strong stick? No, it's totally reversible. All you'd have to do is go in and if you see two of them stuck together, you know, just give it a little flick and they'll totally separate. These chemical bonds aren't very strong, but they're strong enough that, you know what? They exist. And those chemical bonds between the entire molecules of water, those are called hydrogen bonds. How cool is that? And I'm about to give you a list of characteristics of water that all of them exist because of hydrogen bonds. We know water is essential to life. We know that we are essentially like 60 or 70% water. Like most of you, more than half of you, and if you're hydrated even more of you, is actually just water. And then you've got your cells that are floating inside the water, but they're also filled with water. Like you're just a water bed. You're like a giant water bed. That's kind of a fun thought. So let me tell you about some characteristics and keep hydrogen bonds in mind when we're talking about this. Wow, I ran out of paper. Good thing I can go this way. All right, characteristics of water. First of all, water, the temperature, does not change. Now, really doesn't, yeah, whatever you know what I mean. This is Wendy's style, change. I think that's a legit, like, chemistry term for change or a symbol for change. The temperature of water is difficult to change. You have to apply a great deal of heat, fire, to water in order to get the temperature to change. Why? Remember what temperature was? Remember that temperature was just a measure of the molecular movement of the molecules? Our molecules are moving. So a pot of water at, let's say, 50 degrees Celsius, that pot of water has molecules that are moving at a certain speed. They've got a certain amount of kinetic energy. If I put in, let's say, you know, 1,000 calories, that's a measure of energy of heat. So I'm going to add 1,000 calories of heat to my pot of water. Then, I don't know, I'm going to turn it up to, let's just say it goes up to 75 degrees Celsius with that much energy. And let me tell you right now that these numbers are completely crazy and inaccurate. But I'm just giving you an example so that you can visualize this. Let's add some heat. Let's move these molecules around. Let's move up to about, you know, 75 degrees instead of 50 degrees. If you took something like alcohol, and this is my Wendy symbol for alcohol, if you take alcohol and you start it at the same 50 degrees and you add the same amount of heat to the alcohol, you're going to be at like 5,000 degrees Celsius. Okay, I don't even know if that number exists, it's going to get hot. Alcohol does not form hydrogen bonds with each other. And so it's harder to get water to heat up because they're going to, those water molecules are just going to keep on sticking to each other. Alcohol, throw in some heat and it's going to start moving around like mad. Which is a really interesting thing. Hydrogen bonds mean the water doesn't change its temperature. Hydrogen bonds means more, more. Water dissolves things well. And this means it's an excellent solvent. And a solvent is, okay, so here's a beaker and here's a solution of water with particles in it. Say salt particles or sugar particles. And the water dissolves things really well. If you throw like salt into oil, like you, it's going to be harder to dissolve the salt in the oil. Like it's going to form a little salt pile down at the bottom and you, like mixing it in and getting it to dissolve is going to be really hard. Water, it does a great job. Why? Because water can take, it's got those little hydrogen bonds. They can stick with any polar part of any molecule. If you think about salt, salt is sodium chloride. This is an ionic bond right here that connects these guys and sodium actually becomes a positively charged ion and chloride is actually a negatively charged ion. So think about my little water molecule. H, H, O, except I drew it the wrong way. This is my positive charge that's going to stick to the chloride and my negative charge is going to stick to the sodium and it's going to tear these guys apart. It's going to tear those ionic bonds apart and surround them because everything is sticky and when it surrounds them, that is what dissolving is. So thank you, hydrogen bonds, for helping water be a good solvent. Water is also, this one's a cool one. Water has surface tension. Okay, think about this one. It has surface tension. I'm going to show you a picture of something, something with surface tension maybe. Who's this little friend? Water skipper, my little water skipper, this is water. It's not like hanging out on some trampoline or something. It's actually hanging out on water and it's floating on the water and check it out. Is it sinking on the water? Like I would if I tried to stand on top of it. No, it's floating and it's actually floating on top of what to the water skipper feels like a solid surface. Why? Because the surface of the water has hydrogen bonds formed between all those water molecules and you can stand on them if you aren't very heavy. If you're heavy, you're going to sink to the bottom. If you want to know something terrible that you should never tell a small boy child that lives in my house, you can actually, substances like soap, break down hydrogen bonds and you can take a drop of soap in that water that that little water skipper is like sitting on and the soap molecules will come in and connect to the water and break those hydrogen bonds apart and guess who's going to sink? True story. My little friend, the water skipper, is going to be at the bottom of the pond going, what, what, how'd that happen? Yeah, that's going to be mean. And then you better rescue him and wash him off so he doesn't have any soap on him anymore and stick him in a new pond because otherwise he's going to die. Don't do that. Okay, that's good. Yeah, that's good. And then here's the other characteristic of water and again, we're talking about waters, the characteristics of water that allow for life. This one's a weird one. Solid water floats on liquid water. And if you think about that one, that's actually, that's crazy. Most substances, they're solid. They form a solid substance by making, like, strong chemical bonds between the molecules and they become more dense and they sink in their liquid counterparts. Water, solid water, because of the way the chemical bond forms in frozen water to make it a solid substance, it floats. And if it didn't, lakes would freeze from the bottom up. Like, they would freeze on top and then all that frozen ice would sink to the bottom. And then what would happen to all my fish? Dude, it's freezing from the bottom up. The fish have no place to, like, hang out in the winter and they'd all die every winter. Unless, I mean, unless the temperature was warm enough, like, it didn't freeze for very long. But how would you ever melt the bottom of the lake? Like, your whole lake would have to get, it's crazy. There are so many interesting ecological phenomena that occur because solid water floats in liquid water. Like, every year you get this crazy turnover of the lake which swirls around nutrients and brings them to the surface so that critters can survive in the surface layers of water because there's enough food there for them, it's wild. So that's another characteristic that's really important. Water, super important. Nine million application questions that I can ask you about the properties of water. Now we're going to talk about molecules dissolved in water that are important to life.