 Here everybody, Dr. O here, in this video we're going to cover what I like to call the life giving properties of water. If water wasn't so special, then life wouldn't exist. It is that simple. Water is that critically important. Water is the most important molecule of the body, about two-thirds of your body weight. Fifty to seventy percent of your body is water. It's required for all physiological functions, all chemical reactions. They require water. So what makes water so special? It's polar nature and it's hydrogen bonding capabilities, the two things we're going to talk about here. So here we see just a body and different parts of water, but the key things we're going to cover when it comes to the human body are solubility, reactivity, what's called its high heat capacity and lubrication, but I have a few more I'm going to add as well because they're very important to the world around us too. So here we saw a solution. So water is considered the universal solvent and that's why when we're looking for life on other planets, we're looking for evidence of water because without water, this universal solvent, it doesn't appear that life could exist. So the solution is going to be a solvent plus one or more solutes. So water is the universal solvent in the human body. So what determines what's a solvent, what's a solute, that's going to be the amount that's there. That's why there has to be so much water in your body. That's why it's the solvent. Kool-Aid's an example I often use. The water would be the solvent, the Kool-Aid packet and the sugar would be the solutes. Unless you chew your Kool-Aid because you put so much sugar in it, water would be in the most abundant, so water would be the solvent and the Kool-Aid packet and the sugar would be the solutions. Solutions don't have to be liquid. Air is a solution, so the solvent and air is nitrogen because it's about 80% of what's in the air. So it doesn't mean it's the most important thing, just the most abundant thing. So we already said water is the universal solvent. All essentially, almost all chemical reactions occur in water. Here we see the fact that because water molecules are polar, they're going to repel non-polar molecules like oil. So oil and water don't mix because water is polar and oil is non-polar. So that's going to be a big deal with digestion and why we have to have bile. We'll cover that later. The high heat capacity of water, making it a heat sink, very important. Before we talk about humans, you know, obviously about 70% of the earth is covered in water. That's the reason that our temperatures don't get too hot during the summer because all that water absorbs excess heat and holds on to it without boiling away. And then it's also why our planet doesn't get too cold during the winter. Imagine if it got to be 200 or 300 or 400 degrees during the summer and minus 200 degrees in the winter. Well, it doesn't happen because of water. Water takes all the excess heat during the summer and then it gives it back during the winter, which is why places like San Diego are so nice. They're by all this water that keeps them getting too hot and keeps them getting too cold as well. But in the human body, very, very important, your blood, which is full of water, is warmer than the rest of your body. So you can use this warm blood to get rid of excess heat when it's too warm or store extra heat when it's cold. And then on top of that, like you see here of these runners, we have what's called sweat evaporation. So sweat's going to be released warm water onto the surface. As it evaporates into the air, it carries heat energy with it. So the water in your blood allows for maintenance of temperature in your body to begin with. But then on top of it, sweat evaporation will pull heat from your body as well. So very, very important property of water. As water functions as a lubricant and a cushion, right? I have water in my eyeballs protecting me. There's water all over the place that functions as a cushion. But it also has a lubricant. Just like this hinge needs some oil, you've got the synovial fluid inside your joints are going to be the oil in your body's hinges, your body's joints. Plural fluid around your lungs, pericardial fluid around your heart. Their job is to decrease friction and keep there from being irritation when your organs move. You have digestive juices produced every day to keep things moving through your GI tract. Water, cerebrospinal fluid, which is mainly water, cushions your brain and spinal cord. The amniotic fluid that protects the developing fetus. These are all examples of water as a lubricant and a cushion. So those are all very, very important. Here's one that's kind of interesting. Because of hydrogen bonds, solid water, ice is less dense than liquid water, which is why ice floats. You have to think, why does this matter? Well, if the ice cubes didn't flow at the top of your drink, we'd be in serious trouble. Because ice floats, bodies of water freeze from the top down, not the bottom up. If they froze from the bottom up, it would kill all life in the aquatic ecosystems and it would be frozen solid. Imagine our oceans basically being frozen solid all the time. During the summer, the top two or three feet of water could potentially thaw, but then it would just freeze again in the winter. So imagine a lake or a pond frozen all the time. So the fact that ice floats is what keeps aquatic ecosystems safe and also insulates the water so it doesn't freeze all the way through. So you might think ice cube floating on your glass is not that big of a deal, but the principle behind it is. And it's the hydrogen bonds that actually do that. Here we see the adhesive nature of water. You have an insect walking on water. You could set a pin on water. That's because water has this cohesive nature or adhesive nature, meaning that water molecules are attracted to one another. So when you pull on, there's resistance there, which is why that bug can sit on that water. But here you see what's called capillary action. As you pull water, it pulls the water molecule behind it and behind it and behind it. Why does this matter? Well, if you didn't have this adhesive nature, then transpiration wouldn't work, right? The fact that as liquid, as water evaporates from leaves, it actually pulls the water molecules below it up. And that's how plants are able to pull water through the root system up a plant. Like you ever thought about how a tree gets water to the top of it? Well, it's this adhesive nature of water. So these are just so like I said, water is unbelievably special and has all these life-giving properties. If water wasn't amazing, then life wouldn't exist on this planet and life certainly wouldn't exist inside of you. So just remember that the polar nature of water is important, but hydrogen bonds are critically important. Because if there weren't hydrogen bonds, water would behave differently. And if water behaved differently, life wouldn't exist. All right, so those are the life-giving properties of water. I hope this helps. Have a wonderful day. You blessed.