in this video we'll talk about properties of water and this is all standard level or Core Curriculum at most temperatures on earth water is in a liquid state and that's going to be really important because almost all of the metabolic reactions that happen in our cells um take place with molecules that are dissolved in solution so amongst these water molecules um and that's a very important quality of water to keep an eye on now when we're drawing a water molecule we really want to draw it in this form here and I can even label this this is an oxygen and two hydrogens that's how we get H2O but it's useful to look at more of a a chemistry diagram if you will so the oxygen and the hydrogen are bound together through a calent bond but there's an unequal sharing of electrons and those electrons um are pulled a little closer to this um oxygen than to the hydrogen and that results in part partial charges so this is how we would write those partial charges oxygen is going to have a partially negative charge and hydrogen ends are going to have a partially positive charge so this is the way that I would want to draw a single water molecule now notice that I've chosen to draw that coal bond with a solid line that's the proper notation that um consists of a bond within a water molecule between two separate water molecules we're going to have a special type of bond called a hydrogen bond and we use a dashed or dotted line for a hydrogen bond and a hydrogen bond is an attraction between the partially negative end of one molecule and the partially positive end of a different molecule and so that's very important here if I have to draw multiple water molecules I want to be able to not only draw their partial charges and not only draw what atoms exist in there that's a little tough to read there but I also want to be able to draw that hydrogen bond that is going to exist between them and that hydrogen bond gives water some very special properties and that includes cohesion so cohesion um is an attraction between two molecules that are the same so water being attracted or sticking to other water molecules and that is a result of this hydrogen bonding that we're seeing here between these water molecules so cohesion water sticking to other water molecules and that's very important for a few reasons one of which um being what we call transpiration and this is a process that happens in the xylm of plants so the xylem is a tube that goes through a plant and it's the way in which water and other dissolved minerals is going to travel up through the plant and it really starts with evaporation from the stamat so we'll learn more about that in another chapter or sorry another topic um but these stamata are little openings in the plant leaf and when water evaporates from that plant it's also going to pull other water molecules up through the xylem due to cohesion so if you can imagine a water molecule up here pulling another water molecule up with it and that's going to create this tension this pulling force and that's going to pull water all the way up through the xylm of the plant as long as we have a continuous water column so as long as one water molecule is in contact with the water molecule right beneath it it's going to be able to create that tension force and pull the water up through the xylem of the plant all due to cohesion now not only is cohesion important for the insides of some organisms but it's important in creating habitat space for others so here we can see um this insect living on top of the water it's not floating in the water like you and I might float in a swimming pool it's not getting wet it's not even breaking the surface of the water so what that looks like is something like like this where the water molecules actually Bend um when coming in contact with like the foot of the insect I have no idea what this insect's foot looks like um but that's all due to this force of cohesion right these water molecules are hanging on to each other so tightly that hydrogen bond is so strong that that water doesn't even break and now this organism can utilize the surface of the water as a habitat space now you may have noticed when you put water into a tube like a graduated cylinder it doesn't form a line straight across but rather this like u-shaped bit here right so it looks more like this we call this the meniscus and this is all due to something called capillary action and capillary action is a result of adhesion so adhesion is the attraction between water molecules and a solid surface so in this case an attraction between the water molecules and the side of your tube and what that's doing is that's pulling the water up well as you can imagine that's also very important in transpiration for plants so not only is cohesion water pulling water important but also adhesion water sticking to the sides of this xylem that's super important because that helps pull water up against the force of gravity maintaining that moisture content in plants and helping plants move water from the soil up through their xylem another important quality of water is its ability to act as a solvent okay so just some quick vocabulary practice here a solute is what is being dissolved a solvent is usually a liquid acting as whatever we're dissolving something into and the solution is the resulting homogeneous mixture of these two now some things make better solvents than others water is not the universal solvent okay it's a very very good solvent but it cannot dissolve everything it can only dissolve things that are hydrophilic so Hydro meaning water and filic meaning love these are water loving things and these are going to be either polar molecules like glucose or ions things that have a charge so water is polar it loves other things that are also polar or have a charge that's in stark contrast to hydrophobic Hydro meaning water phobic meaning hating these are water hating substances so these are going to be nonpolar things so things like lipids or things um like an oxygen molecule um that have very low solubility in water now metabolism all of those reactions that happen in our cells requires things to be in solution so the fact that water is able to dissolve so many types of things makes it a really good medium for life and again this is all because water is polar so what we want to do is start associating the property being a good solvent with the property of water which is water is polar so that we can start to see the connection between what physical properties water has and how that's helpful to living things because water is such a good solvent that makes it an ideal transport medium in both plants and in animals so in that plant we're going to have two tubes we talked a little bit about the xylem so the xylem is going to carry water and dissolved minerals the phum is going to carry things like sucrose or other carbo hydrates but they have to be in solution so when we say in solution they have to be dissolved in water so water is a very good medium for dissolving things and getting them to flow through the different parts of the plant same thing happens with animals um we have a blood transport system and water makes up the primary component of what we call our blood plasma so our blood plasma is the liquidy part of our blood and it is primarily made up of water so that means it's going to be a very good solvent for things like ions glucose amino acids things that are hydrophilic things like oxygen or things like fats or cholesterol they have to be carried by things like cells or proteins because they are not very soluble in water so we'll replace that terminology here okay things that are hydrophilic are soluble and we are going to find them um in the blood plasma okay and things that are not soluble we're going to find them attached to things like proteins or cell components so that they can be transported another important physical property of water is buoyancy so gravity or gravitational force is going to be exerted downward it is buoyancy that is the force moving in the upward Direction so a force exerted upwards on an object by that water and so if done correctly or if in the right balance this leads to objects or organisms being able to float so less dense objects are going to be able to float on water the buoyancy of water is greater than the force of gravity exerted on the water and so those will float denser objects will sink most aquatic organisms are going to have about the same density of water and they don't want to be really stuck at the bottom or always really up at the top but some organisms can actually adjust their buoyancy so for example this is what's called a swim bladder in a fish and this fish can fill this swim bladder up with air when it does that it becomes less dense and it starts to float if it deflates its swim bladder it becomes more dense and starts to sink in the water so adjusting its own um density to either rise or fall in water all due to Water's buoyancy now let's talk about viscosity or water's resistance to flow so think about a fish swimming through the water we need some resistance from the water when the fin is moving in order for that fin to help the fish Propel itself forward there are also some um implications here for water being used as a transport medium so the more solutes that are dissolved in the water the higher the viscosity so we need to keep that in mind um there are limits to how much we can dissolve into things like blood um before it becomes very resistant to flow the next physical property that deserves our attention is what's called thermal conductivity water is a very good conductor of heat so heat can transfer easily through water that can be good or that can be bad um it just depends on the scenario so sometimes it's great if there's a lot of metabolic activity happening in our cells some of that blood plasma right that watery based solution that we talked about just a bit ago can pick up some of that water and then transport that heat maybe to the surface of our skin okay but having that heat energy enter that water very easily and then be transported in that way can be great it can also have some dire consequences if I'm um falling into an icy Pond um or a very cold body of water that water again is a good thermal conductor it can take the heat from my body and that heat will then be transferred into that water so in that case it can be bad so when we say the consequences for animals in aquatic habitats um sometimes that's great and sometimes that's not so we just need to consider um water is a very good thermal conductor and organisms will have to have adaptations to either take advantage of that or to prevent losing too much body heat um into that water although water is a good thermal conductor um it doesn't actually change temperatures very easily so water has what's called a high specific heat capacity and that means that it can actually absorb a lot of heat energy without a drastic change in energy so it has a high specific heat capacity it doesn't change temperatures as easily as other things like an alcohol or methane or something like that this is great if you are an aquatic organism so it has what's called a moderating effect I would definitely put that in my memory bank a moderating effect means that you can have lots of temperature variation in the air it can go from being a warm sunny day to a nice chilly night and the temperature of the water water won't actually change that much so it's moderating it's keeping that temperature range for that body of water in a relatively narrow range so that's great for aquatic organisms that live in there it can also be great for the maintenance of body temperature so like we just talked about your cells um can produce a lot of heat with um different metabolic reactions so that heat energy can enter the watery parts of your cells the cytoplasm or even the water-based fluid the plasma in your blood and that won't change temperature very much again you'll see some organisms that live in really hot areas um like this African elephant the reason that they have really big ears is to be able to expose those ears and the blood that's inside them to the outside air so yes water is a good thermal conductor it can exchange heat with the environment but the actual water itself so the blood plasma won't change temperatures um drastically so what does this look like in practicality well let's talk first about this ringed seal this ringed seal lives mostly in the water and water is very buoyant so that's great the seal can float and it doesn't have to expend a lot of energy to do that but water is very viscous so in order to move through it it does have to expend energy that way water is also a very good thermal conductor so what you're going to see here on seals is a large amount of blubber or fat that helps prevent some of the body heat from inside of the seal um being transmitted to the water in the environment so different adaptations for different environments this is the Arctic loon and it's evolved to live in the air air is less buoyant than water so that loon has to expend a lot of energy in order to stay um a loft to stay in the air but air is less viscous than water so it doesn't take as much energy to move through that air okay air is also not as um great of a thermal conductor so we're going to find less things like blubber on that bird but great examples of the ways in which organisms and especially animals in and near these aqu habitats have different adaptations to deal with the pros and the cons of these physical properties of water