welcome to the lecture for chemistry for general biology biology 1010 at laramie county community college today we're going to be talking through first the very basics of how atoms are structured and how that contributes to their properties and also how they're able to bond and then we will also look at the properties of water which is a supercritical element in terms of how biology works at the chemical level so starting with the very basics everything in the universe is made up of matter including organisms which we care about for this class so matter is anything that takes up space and has mass and more specifically that matter is made up of different elements and those elements each have a different atomic structure and different properties because of that and we call them elements because they cannot be broken down any further into anything else stable in any given element has the particular pieces that make up an atom and the numbers of those pieces it has is what contributes to its properties so looking at an atom for all atoms with the exception of one we will have three different parts go into the composition so in the nucleus different from nucleus of the cell were much much smaller at this point so in the nucleus of an atom which means in the middle we have two different types of compounds here we have the positively charged protons which are shown in red and then we have the non-charged neutrons that are shown in black and then circling that nucleus in what we're going to call an orbital because they're basically orbiting around that nucleus are negatively charged smaller particles that we call electrons overall depending on what element that we're talking about you'll find these three pieces and we can always find them in the same pattern and so as i mentioned on the last slide there is one element that doesn't have all three that is hydrogen you'll notice this guy just has one proton and one electron he is missing neutrons okay so hydrogen is our exception for everybody else they're going to have protons neutrons and electrons and unless we tell you differently when we're talking about particular exceptions to the rules of where we start um you'll always set up your atom with the same number of each of these parts and so when we're looking at oxygen here you'll notice he has eight protons eight neutrons and eight electrons and those are always going to be arranged in a specific pattern the protons and the neutrons are always found in the nucleus and then the electrons are going to be found in those shells that are allow the electrons to orbit around the nucleus the same way that we see orbiting happen in our solar system so to get more information on how these different pieces are arranged as well as what the properties are that those elements end up having chemists studied this for a while noticing that different atoms behave differently when they're in when they interact with other ones um and ultimately dimitri mendeleev was able to arrange them showing how we see similar behavior in terms of of those atoms and he has element 101 on the periodic table named for him mendelian but he was never awarded the nobel prize so it's a good reminder that even though we we really talk a lot about how science is impartial and free from bias keep in mind science is done by scientists and so there's always some messiness in there still okay so when we're looking at the periodic table it's going to provide us some information that's going to be important for you to be able to make predictions about how you expect these atoms to interact with each other and so on the periodic table you're going to see zooming into any given little square you're going to see a few key things so the first one is actually a symbol and each symbol is unique to a given element and that is going to help tell you what its name is sometimes the whole name is listed like i have shown here but sometimes it's not and so you may have to do a little bit of extra work if you have a periodic table that doesn't show the element name but c is the symbol for carbon the other pieces of information that we can see on here is it has an atomic number up here at the top and this is the thing that we're probably going to focus on the most for this class so looking at the atomic number is always going to tell us the number of protons in addition it's also going to give us the number of electrons and neutrons that we start with unless i give you some additional information telling you that it's a different version of that atom so by default we will always use the atomic number to tell us for sure how many protons we have but also how many neutrons and electrons we also have um but key point here the protons do not change if the number of protons change then the element changes okay so if we add a proton or subtract a proton then we're going to have a different element if we add neutrons or electrons we can still have the same element okay as long as the atomic or i'm sorry as long as the number of protons stays the same the other number that you'll see on here is the atomic mass and this is actually the average weight across all of the different forms of carbon that are out there and this is adding together the protons and the neutrons the average that's shown on the periodic table is not going to be super helpful for us in this class but you will use it when you go into chemistry when you're trying to identify unknown samples but for our purposes we're going to be calculating our own mass instead of looking at the averages so before we start talking about how the different atoms are able to bond to each other we also need to talk a little bit about how the atoms can change themselves so reminder a few slides ago i mentioned that if we change the number of protons we change the element and so we're not going to talk anymore about that piece but the other two parts of the atoms can be changed without changing the element itself and so if we change the electrons that's going to be the first thing we talk about here with ions and we can also change the number of neutrons and so we'll talk about both of those first and then we'll come back to what that looks like for how these elements interact so when the electrons get changed the atoms actually change into what we call an ion and an ion is a charged atom so let's think about that for a second so if we take carbon our example that we saw earlier it has an atomic number of six okay and so what that means is it has six protons one two three four five six so it has six positive charge it also has six electrons okay so looking at this we have an overall neutral charge because each positive has a negative that's able to cancel it out so an element can become an ion when the number of electrons gets altered and so if it loses an electron you'll notice now we have six pluses and only five minuses so that extra plus is going to make the atom positively charged and when it is positively charged we call it a cation okay or it can pick up an additional electron so in this case now six protons and seven electrons that's going to give it an overall negative charge and we call negatively charged atoms anions okay keep in mind good spot to watch for a misconception remember that the protons don't change so we're never going to be losing or gaining a proton to become an ion right that will change the element if we added a proton here then it's no longer carbon and it has to become nitrogen so when we're talking about ions we are talking about gaining or losing electrons which change the number of charges available okay so always keep that in mind only the electrons change we don't add a proton to get a positive charge okay we've lost an electron to get a positive charge right so that's our first type of variety and this is just to help you remember the differences between anions and cations cations again are the positively charged one and if you spell it positively then that might help you remember that it is a cat ion okay so the other thing that we need to consider as we're talking about electrons is that of course electrons don't just appear out of nowhere or disappear they're a functional you know piece of matter that has its own energy and so when we're talking about these elements becoming ions because they gain an electron or they lose an electron we need to kind of back up just a little bit and think about the idea that if something is gaining an electron it came from something else that lost it and vice versa and so we will talk about this concept of electrons moving a lot throughout this course because a lot of how energetics work in biological systems is via electrons moving around and so we're just introducing this here so we can use the correct terms as we're talking about this so when an electron moves from one thing to another we call that a redox reaction and it has that name because it's the combination of a reduction reaction which is something gaining an electron okay and an oxidation reaction which is something losing an electron and i know this term reduction seems a little counterintuitive because it seems like if something's reduced it would be less but the reduction itself is actually talking about the reduction in charge so when something gains an electron it becomes more negative okay and just a a little acronym here to try to help remember this oil rig is oxidation is loss and reduction is gain and again we will come back to this many many times but i just wanted to introduce it here so that we can talk about something being oxidized when it loses an electron or something being reduced when it gains an electron okay so our other piece of that can be altered on an element is the neutrons and so different forms of the same element that have different numbers of neutrons are called isotopes okay so just a reminder one more time protons don't change when electrons change we get ions when neutrons change we get different isotopes okay and this is where that atomic mass comes into play so if you remember back when we talked about the uh periodic table and when we're looking at that little box of information about a given element it has an atomic mass on there that's the average of all of the isotopes so again that's not super helpful for us when we want to look at a specific individual isotope and so instead we're just going to calculate the mass individually for which isotope we're talking about and so regular carbon i'm doing air quotes i know you can't see that so regular carbon remember carbon has an atomic number of six right so that means it has six protons six neutrons six electrons to start with and so we actually call this version of carbon carbon-12 because we're going to add together the protons and the neutrons to get its mass and so another isotope of carbon is carbon 13 and reminder we cannot change the number of protons because if we do it will no longer be carbon and so the only way to get that additional mass unit is to go up with neutrons and so now we have six protons plus seven neutrons to give us our mass of 13 which gives us carbon 13. and of course then we can keep going up so carbon 14 six protons eight neutrons or you could potentially also have some isotopes where your mass goes lower so if we had six protons and five neutrons then that would be carbon 11. okay all right so that's all in terms of what we're going to talk about for atomic structure for an individual element with those three pieces protons neutrons electrons so now we're going to switch gears a little bit and talk about how these different things interact with each other and so a compound is the term that we give for a combination of two or more elements that are bound together in some way sometimes you will also hear the term molecule being used it's kind of a personal preference and you'll actually hear me use both of those okay so this is actually one of the first places where we're going to start seeing the idea of emergent properties in from a chemical perspective and just a reminder what emergent properties means i'll write it up here emergent properties is when two or more things come together and then they have new properties that neither of the individual things had by themselves okay and so it's something we definitely see as we look all throughout biology when we have changes in cell types and then tissue types and then organs and we end up having something be able to do something when it's working together that pieces couldn't do individually excuse me so for example your bones by themselves give you support your muscles by themselves have contraction but when we have muscles pulling against bones we get movement right so neither of those things were able to move you know walk across the room by themselves okay so that's kind of that idea so the example i have for you here most of us are familiar with what we have over here on the right which is table salt and chemically that is sodium chloride okay and of course this is we have it all the time this is one of our main sources both of sodium and of chlorine that we have in our diet both of which are essential but if we look at these two elements individually they're very very different so this is pure sodium over here it's like a soft gray metal and it's actually explosive in water and so it is not safe to consume in pure elemental form and this in in the middle here is chlorine pure chlorine which is gas at room temperature and you've probably smelled it before if you've walked into a pool or you've ever smelled bleach or something like that where chlorine is being used to actually destroy cells and so we're using it as a an antiseptic in that case and so also you know concentrated chlorine gas is actually considered a weapon of mass destruction so it can wipe out an entire town if enough of it is deployed so bad bad stuff yet when we put these two together they leave behind their dangerous properties that cause cause cellular damage because they actually kind of balance each other out and make it a more stable form that we're able to consume and not do harm to our bodies so great example and so just again thinking about as we start talking about compounds and more complex molecules as we work our way towards building you know cells and organisms and throughout our time together this semester just keep in mind we're going to see this change over and over again how things can take on new new properties so now let's step aside from the properties a little bit and let's get back to how is it that we can determine when something's going to bond and also how it's going to bond so when looking at any given element the most important feature that we're going to look at to make predictions about how that element is going to interact with other elements in terms of bonding is actually its outermost electron shell and so that one has a particular name we call it the valence shell and just a reminder that in terms of what we're looking at for this class we're only going to use three shells okay and so just a reminder again the first shell if this is our nucleus are in the middle of our atom the first shell can hold two electrons the next shell can hold eight electrons and the outermost shell for our purposes can also hold eight okay so depending on how many electrons your element you know that we're interested in has they're always going to fill from the center and then overflow to the next shell and so in the case of what we have hydrogen up here has an atomic number of one so it just has one electron and therefore its valence shell is going to be this innermost one two and the goal the goal air quotes i know you guys can't see me doing that um is to have a full valence shell so whichever shell happens to be the outermost one for that given element it wants to have a full shell and so that means either stealing electrons giving away electrons or sharing electrons those are the three possibilities in terms of trying to get more or less electrons into your outermost shell so in the case of hydrogen we know that that first valence shell holds two electrons and he already has one and so he wants one more to be able to have a full valence shell with the number of two and so hydrogen will always form one bond with something or it will give away its electron and have no shells that's really the how hydrogen likes to play and if we look down here with another example oxygen you'll notice it has an atomic number of eight and so again we kind of default to using that number of electrons unless we have additional information so it's gonna have two in its first shell and then it's going to put the rest of its electrons that it has in its next shell so it has six left one two three four five six but reminder that second shell is able to hold eight and so now that tells us that oxygen needs two more electrons to have a full outer shell and so we will typically find it either taking electrons or sharing electrons with two things so that it can get two total electrons in that valence shell and therefore have a full outer valence shell okay so any element that we're looking at we can look at how many shells should it fill and then how many additional electrons are needed to get a full valence shell all right so this is like a tiny version of the um periodic table where we've kind of shrunk out all the middle stuff because all we care about is the the first three rows in terms of what we're learning in this class and so again reminder first shell holds two second shell holds eight third shell holds eight and we can see that right so here's our first shell and hydrogen has one helium has two so he's good to go second shell here you can see lithium only has one in that second shell and so that's going to be really hard for him to gain seven um to have a full outer shell and so he's more likely to just lose that outer one and drop back down to just having the inner shell of two electrons and so he's typically going to become a cation whereas over here on the other side you can see fluorine has an atomic number of nine so two in the first shell and then seven in the next shell so he only needs one oops he only needs one to be able to have a full outer shell and so he will either bond with something and share it or he'll steal that electron um and become an ion so that he can be stable okay and so always just whenever we're talking about how something is gonna bond you're gonna just look at okay what's the atomic number and then fill those shells with electrons two in the first one everything that's left overflows into the second one and if what's left is more than eight then it overflows into the third one okay and then we look okay how many spots are still open and that's going to give us a clue of how many bonds will form and so i mentioned before that we were going to ignore that last column on the periodic table because they don't play with anybody else and now you can kind of see why right so helium has two electrons already in its shell which means it already has a full valence shell and it's completely stable on its own it doesn't bond with anything because it doesn't need any electrons it doesn't need to get rid of any electrons so helium is already good to go same thing with neon has an atomic number of ten so its first shell has two its second shell has eight it's already completely stable and it doesn't interact and then same thing with argon so for those of you who have inhaled helium out of a balloon at some point and didn't stop to think about possibly the dangers of inhaling some type of other element lucky for you helium is completely stable and therefore doesn't steal electrons from any of the parts of your cells in your lungs and and it just will evaporate out of of your lung space especially because it's lighter weight than most of the air that we inhale but if you in hot inhaled fluorine for example it would tear electrons from cells all throughout your lungs it probably would kill you i would think pretty short order unless the concentration was super small so again the idea of this is just always remember for the purposes of this class we're only going 288 when we get past that some things kind of rearrange a little bit which you'll learn when you get into chemistry but you can always take the atomic number and then look at what pattern of distribution do you see in the the shells and then how many slots are still open in the valence shell to make a prediction how for how things are going to bond all right so we're going to talk about three different types of bonds the first two covalent and ionic are between elements and so both of these are going to hold elements together to form compounds whereas hydrogen is bonds are actually between compounds and so that one's going to hold smaller compounds to each other which can give them that water for example is the main one we're going to talk about give it some specific properties so let's talk about covalent first so covalent bond is the sharing version okay so this is when two different elements are going to share electrons so that everybody can have full outer valence shell at least some of the time and because they're sharing and those electrons are traveling around in those orbitals encompassing all of those elements that are participating it is the strongest chemical bond okay so you can kind of picture almost just like as these electrons are just spinning around super fast they're kind of holding you know all of this together right and so it results in this nice strong bond and cool thing about that is they don't have to necessarily just share one pair so in the case of hydrogen of course reminder atomic number of one that means it needs to fill its first shell and each hydrogen only has one and so it needs to share or take another one and so here we can see two hydrogens and they're each going to share their one electron with the other one some of the time so now they both have two electrons some of the time and this is a stable i mean relatively stable bond hydrogen gas is kind of explosive um but everybody's happy here in terms of stability the valence shell is full for both of them so in comparison if we look at oxygen again atomic number of eight and so he has two in his first shell and then he has six in his outer shell he needs two to be full and so when we look at oxygen gas the only way that they can have full outer valence shells is to actually share two with each other so this oxygen is going to share two with this guy and this oxygen is going to share two with this guy and so in that way by sharing two pairs instead of just one pair now everybody again has a full outer valence shell at least some of the time and so we call that a double bond where they're sharing two pairs of electrons and you can even go up to triple or a quadruple bond as well okay our other type of bond is an ionic bond and we can tell just by that term that we see up here with ion in it that it's going to have something to do with charged atoms okay and so to have an ionic bond you have to have charges first and basically this is just when these two differently charged ions so a cation and an anion are attracted to each other based on charge you can think of it just like a magnet okay so not the same as a covalent bond because there's no electrons being shared there's no physical connection between the elements and so the only thing holding them together is charge so if any other charges come in there that can interfere as well okay so let's take a step back for a second and just again refresh on how we get ions in the first place and a great example of that is looking at sodium and chlorine so sodium atomic number of 11 up here and so he has two in his first shell eight in his second shell and then just one in his outer shell and so of course the goal is for him to have a full outer valence shell that's a pretty hard hill to climb when he needs seven additional electrons to get a full shell of eight and so instead sodium just gets rid of that electron okay so he becomes oxidized reminder if we're using our correct terms there um and so then he becomes a cation right because now he has 11 protons so he has 11 positive charges but he got rid of one of his negatives so he only has 10 electrons so there's one extra positive charge therefore he becomes a cation okay and one of the things that is all too happy to pick up that electron from sodium is chlorine and so chlorine has an atomic number of 17 and so two in his first shell eight in his next shell and then seven in his outer shell so he only needs a single one to have a full outer shell so chlorine is happy to take that extra electron from sodium he becomes reduced reminder because he gains that electron and so now chlorine has 17 positive charges and he has 18 negative charges so he is an anion okay so now because of this we have one positive charge and one negative charge and they stick to each other based on charge okay so i just have a quick video for you that's going to review the covalent and ionic bonds and show you some cool examples and then we will move on to hydrogen bonding [Music] most atoms don't ride solo instead they bond with other atoms now bonds can form between atoms of the same element or atoms of different elements you've probably imagined bonding as a tug of war if one atom is really strong it can pull one or more electrons off another atom then you end up with one negatively charged ion and one positively charged ion and the attraction between these opposite charges is called an ionic bond this is the kind of sharing where you just give away your toy to someone else and then never get it back table salt sodium chloride is held together by ionic bonds every atom of sodium gives up one electron to every atom of chlorine ions are formed and those ions arrange themselves in a 3d grid called a lattice in which every sodium ion is bonded to six chloride ions and every chloride ion is bonded to six sodium ions the chlorine atoms never give the sodium atoms their electrons back now these transactions aren't always so cut and dried if one atom doesn't completely overwhelm the other they can actually share each other's electrons this is like a potluck where you and a friend each bring a dish and then both of you share both dishes each atom is attracted to the shared electrons in between them and this attraction is called a covalent bond the proteins and dna in our bodies for example are held together largely by these covalent bonds some atoms can covalently bond with just one other atom others with many more the number of other atoms one atom can bond with depends on how its electrons are arranged so how are electrons arranged every atom of a pure unbonded element is electrically neutral because it contains the same number of protons in the nucleus as it does electrons around the nucleus and not all of those electrons are available for bonding only the outermost electrons the ones in orbitals furthest from the nucleus the ones with the most energy only those participate in bonding by the way this applies to ionic bonding too remember sodium chloride well the electron that sodium loses is the one furthest from its nucleus and the orbital that electron occupies when it goes over to chlorine is also the one furthest from its nucleus but back to covalent bonding carbon has four electrons that are free to bond nitrogen has three oxygen two so carbon is likely to form four bonds nitrogen three and oxygen two hydrogen only has one electron so it can only form one bond in some special cases atoms can form more bonds than you'd expect but they better have a really good reason to do so or things tend to fly apart groups of atoms that share electrons covalently with each other are called molecules they can be small for example every molecule of oxygen gas is made up of just two oxygen atoms bonded to each other or they can be really really big human chromosome 13 is just two molecules but each one has over 37 billion atoms and this neighborhood this city of atoms is held together by the humble chemical bond all right so again just a reminder kind of thinking about we can look at the periodic table and we can make predictions about what we expect to happen with those atoms so again looking at the guys that we see over here they all have one electron in their outermost shell and so they're likely to lose that and become cations whereas these guys over here only need one additional electron to have a full outer shell so they're either going to bond with one thing in a covalent bond or they're going to steal an electron and become anions okay all right so that kind of gives us an overview of making predictions of how things are going to happen and now let's go ahead and talk about what happens with a hydrogen bond which reminder is between molecules instead of between elements and so this also is going to play a role with the electronegativity that we talked about before so you'll see the arrows on there again um just a reminder things get more electronegative as we go to the right and more electronegative as we go up and so the things that are over in this area are the most electronegative on the periodic table meaning that they can take electrons from pretty much anything else okay so in the case of some of these compounds they can still form covalent bonds however because one of the partners within that covalent bond is so much more electronegative than the other one it actually hogs the electrons more than half of the time okay and so for example if this was hydrogen which is on the far left side of the periodic table and this is oxygen which is on the far right side of the periodic table the shaded color that we're seeing here is that the electrons are spending more time on the oxygen side creating a slight negative charge and because the electrons spend way less time on the hydrogen side it creates a slight positive charge okay when compounds do this we call them polar so that means it's an unequal sharing of those electrons resulting in slight charges okay now to get to the actual hydrogen bonding piece when things are polar and they have those slight charges then those opposite charges can be attracted to each other just like we saw with ionic bonds so let's look at that water is a great example of this excuse me so this is our water molecule i'll draw another one here just so we can label it okay so the big side is the oxygen and the little sides are the two hydrogens reminder that water is h2o okay two hydrogens one oxygen because the oxygen is so much more electronegative it hogs the electrons so it ends up with a slight negative charge over here because it's holding those electrons more and because the hydrogens do not have them they get slight positive charges on their side so now where we see the hydrogen bonding come into play is the slight negative on one oxygen of one water molecule is attracted to the slight positive on a hydrogen of a different water molecule okay so now we have this bond holding these two oriented towards each other where the oxygen is facing a hydrogen and then here again we can see another oxygen here is facing a hydrogen here and we have these hydrogen bonds okay so this is the weakest bond of the ones that we've talked about again covalent and ionic are stronger than this and if we're looking at a glass of water in this case you can see within a single water molecule we have a covalent bond but between water molecules we have hydrogen bonds okay and in liquid water these molecules are constantly forming and then breaking and reforming these hydrogen bonds all right so that's going to take us into the properties of water so we just did kind of baby version of chemistry really the fundamentals that you need to know to be able to do biology um at least cellular biology at this level and so now we're going to go through kind of a list of the properties of water that make it so conducive to life because it's actually several things that if water did not behave in a particular way um sometimes in a unique way in comparison with other compounds then we would not have life on earth so what are the properties of water that make it so conducive to life so the first one we've already talked about a little bit the fact that water is polar and because it's polar it has hydrogen bonding between molecules so we'll kind of talk through why that hydrogen bonding is so important in terms of what we use water for in biology it also has a high specific heat and high heat of vaporization and basically what both of those things mean is that it takes a lot of energy to actually change its temperature or change its form so to go from a liquid to a solid or from a liquid to a gas um and so that means that it really can mitigate changes environmentally both for us as organisms but also like for our planet overall and we'll again we'll talk about each one of these a little bit more it is less dense as a solid which is something that's pretty unique most compounds when they become solid they move from liquid to solid they actually become more dense so more tightly packed and then they usually kind of sink within that liquid and so ice is not that way when water becomes solid it actually floats in liquid water instead of sinking and then last thing because this kind of takes us back up to our top here because water is polar and it has those slight charges on both sides right reminder we have that slight negative on the oxygen and we have the slight positives on the hydrogens that also means that it's a pretty good solvent because basically anything that's charged is able to readily dissolve into water so talking through each one and i know we just talked about this but we want to you know revisit it and look at it again so the water molecules are constantly bonding to each other and so even though this bond here is the hydrogen bond which is the weakest bond when you take a whole bunch of little weak bonds and add them up together between all of those water molecules you actually get really really impressive strengths and you guys have probably experienced some of the strength in action before so things like hydraulics that are used in farming equipment or the jaws of life that is making use of the hydrogen bonds between water molecules to really just take that strength or um like a a water cutter where water is able to cut through steel just because of the the strength there and then of course you've probably also seen things like this where you have insects that are able to walk on water based on pushing against that those water molecules holding onto each other and then we also have capillary action and so that's super critical for things in biology so if you think about like a tree like a giant you know sequoia tree that's a hundred feet in the air it has no pump to move water from the roots to the leaves it actually relies solely on this hydrogen bonding where you can basically have these water molecules and they are just bound all the way down the veins of the tree and so as it evaporates out of the top it pulls from the roots down at the bottom and and because of the strength of that hydrogen bond being present it's able to pull it all the way up and of course we also have capillary action in our own bodies as well that's why you have fingers and why you have an ear ears because the the blood itself isn't being pumped by your heart into the tip of your finger it's pumped you know down until your blood vessels get small enough to where that pressure would do damage and from there it's basically wicked using hydrogen bonding so a couple other terms to consider with that with hydrogen bonding water molecules holding on to each other is called cohesion and water molecules holding onto something else is called adhesion and keep in mind again because they're polar and they have those slight charges they will be attracted to anything else that also happens to have a charge so i have another quick video here this is just a short little animation but i think it really does a good job showing the hydrogen bonds so let's play that and i'll talk through it a little bit for you and of course it's from canada so we have our translations in french as well so here this is just the formation of the water molecules and so combining hydrogen with oxygen there we have our water molecules our mickey mouse shape and then again because those of the electronegativity of the oxygen it's hogging the electrons most of the time so water molecules are polar so there we can see the hydrogen bonds kind of forming between a negative oxygen and a positive hydrogen on a separate molecule and again a pretty weak bond so on its own it's just forming and breaking and forming and breaking but when we have lots of water molecules you end up with lots of hydrogen bonds right all together that's going to provide really good strength with water okay so what else is unique about water um so we talked about the temperature aspect that water can absorb a lot of energy and it also can release a lot of energy without having a big change in itself and so you can think about um you know even when you're cold outside or hot outside the water is keeping your body temperature relatively stable and we can also see that environmentally when we look at areas that have maritime climate so places by big bodies of water their average temperature is going to be relatively similar year round because the water is mitigating the increase or the decrease in radiation from the sun whereas when you get away from the water then the temperature really is determined solely based on the input of radiation energy in that case and while that's a great example you know looking at being in the ocean in california this is actually my favorite example when we look at comparison between planets that have water mitigating their atmosphere temperature versus not so let's look at the obvious ones first so mercury up here it's average day temperature 778 degrees fahrenheit average night temperature minus 364 degrees fahrenheit so even though it's right next to the sun the temperature that it has at any given time is solely determined by the energy coming from the sun so if it's facing the sun it's super super hot and if it's not getting input from the sun it's super super cold because there's nothing to mitigate or absorb that energy and retain it and even mars which is nowhere near the sun right close much further than we are has a day temperature of 230 degrees fahrenheit and a night temperature of minus 240 degrees fahrenheit and so both of those temperatures even with mars are completely not conducive to life right that's way past what we can handle and in comparison when we look at earth which has a large amount of water in its atmosphere the average day temperature is 78 degrees the average night temperature is 71 degrees and so that energy is really really mitigated by the water which makes us have a stable environment and allows us to survive here okay and as i mentioned before most things become more dense when they become a solid right the molecules get more tightly packed and so it increases in density water does not do that because of the hydrogen bonding again and so you'll notice here when we're looking at the liquid water you can see the kind of forming um you can see the bonds are kind of irregular there you know some have hydrogen bonds but not all for water to become ice and become solid it actually has to spread out so that every possible bond actually is aligned so that means every single negative oxygen has to be facing towards a positive hydrogen and so to do that they have to scoot out apart from each other to make sure that their shapes are perfectly aligned and so here you see not very much space and here you see lots of space and so in ice it's about 10 percent less dense than water which also translates something maybe a little bit more familiar is it takes about 10 inches of snow to get one inch of water okay once that melts so all right it's nice that ice floats you know that's nice when you have a drink and you're drinking your cold water right first um but we have to kind of think about why this is essential for life on a little bit of a bigger scale so when we look at the water cycle overall the air is always cold enough near the north and south pole that it's constantly freezing water into ice and if that ice sink it would go down to the bottom of the ocean where it is very cold and there's no additional like radiation from the sun that reaches that far down and so it would not be able to ever have enough energy to melt and so if i sink eventually almost all of the liquid water on the planet would freeze solid but instead by it floating and staying up on top of the water it always has access to the increase in radiation energy when the sun is there which allows it to melt and of course if everything was solid that would be the end of the water cycle right we wouldn't be able to have any evaporation and then therefore precipitation over land um to provide us fresh water for all of our terrestrial habitats and so not only is it critical in terms of the water cycle that ice floats but it also protects organisms underneath the ice when we have changes in our environment as well so another quick video this one is actually just kind of showing the molecules but i really like the way that it shows the difference in density between solid and liquid so i'll kind of talk you through this guy so there's just our lone little water molecule zoom in a little bit so we can see him and again still has the one oxygen two hydrogens with the polarity right so slight positive charges on the hydrogens slight negative charge on the oxygen and so what it's showing you here is ice and you can see that the molecules are all really regular they're spaced out they're aligned in a nice kind of crystal structure where everyone's hydrogen bonds are perfectly lined up and as more energy gets put into the system you can see the molecules starting to move more with the energy and there we have a shift to water so you can see how it condenses so much when it becomes liquid and then as more and more energy is put in and the molecules are moving faster and faster they actually have a hard time maintaining any hydrogen bonds and so when we have the shift from liquid water into vapor then the molecules just separate so cool it actually has very funny sound effects but i did not include those for you guys all right so our last property of water is that it is a really good solvent so just a reminder what what we're talking about with that so for something to be a solvent that means lots of things dissolve into it right and so if your cells you know inside your cells is mostly water of course your blood is mostly water and so all of the things that we consume and we need to be shuttled you know throughout our cell or throughout our body have to be able to dissolve into water right it can't float on top of the water or get stuck somewhere it has to go down into it and be shuttled from point a to point b and water is such a good solvent because of those slight charges so again this takes us back to it being polar and how that creates those slight charges which do all sorts of things for us so here you can see this is a chunk of salt so the yellows are sodium and the green is the chlorine and it forms that nice crystal structure and when it goes into water you can see that the positive sodium gets surrounded by the negative oxygens and the negative chlorine gets surrounded by the positive hydrogens and so because those charges are present in water they're able to equally attract the ions because keep in mind we talked about covalent bond where electrons are shared right so that's a very specific connection whereas an ionic bond is just charge and so it isn't sodium liking chlorine it's sodium liking the negative charge that chlorine has but sodium would be equally attracted to any other negative charge right and so that means anything that's charged any of those ions are able to easily dissolve into water and be transported of course across a cell but also throughout an organism and it's not just small things like individual ions but also proteins and a variety of other types of compounds that are necessary for life that have those slight charges and therefore allow them to be dissolved into water so as we're talking about this idea of something being a good solvent i just want to take a pause here and and make sure that we're clear on the semantics and so when something is a solvent again reminder that is the thing that stuff is dissolving into and so the case of cells the solvent that we're going to be talking about like 90 of the time is going to be water but then we can also refer to the specific things being dissolved into that solvent and we call those solutes okay so that would be things like salt and sugar and proteins and then when we combined our solvent with all of the solutes in it that gives us the solution okay when water dissociates it breaks apart into an equal number of hydrogen ions and hydroxide ions in contrast when other substances dissociate they may release more hydrogen ions or more hydroxide ions for example hydrochloric acid releases more hydrogen ions as it dissociates and sodium hydroxide releases more hydroxide ions depending on its concentration of hydrogen ions versus hydroxide ions a substance can be classified as either an acid or a base the ph scale measures how acidic or how basic a substance is it ranges from 0 to 14 with 7 being neutral when a substance has a ph of 7 like water does it releases an equal concentration of hydrogen and hydroxide ions when a substance has a ph of greater than 7 it's classified as a base and releases a greater concentration of hydroxide ions the more hydroxide ions that are released the more basic the substance is bases tend to feel slippery and are often used as household cleaners mocha magnesia and ammonia are both common bases when a substance has a ph of less than seven it's classified as an acid and releases a greater concentration of hydrogen ions the more hydrogen ions that are released the more acidic the substance acids tend to taste sour lemon juice stomach acid and coffee are all examples of acids so just as the video was mentioning anything that gives off either of those parts of water whether it be the proton which makes it an acid or the hydroxide ion which makes it a base we would assign them a ph number okay so let's go ahead and look at some additional examples of those oh no before we go on do you want to point out if an acid and a base are mixed they will neutralize each other right because this extra piece that hydrogen ion there from the acid and the hydroxide ion from the base can come together to form water that doesn't necessarily mean you should always just mix an acid in a base some of them when you mix them together can be super super explosive as that neutralization occurs but for example if you've ever done the volcano experiment where you mix baking soda which is a base with vinegar which is acetic acid um then you get a whole bunch of bubbling and then afterwards you have water and then you know some other molecules left over okay so now let's continue on i do want to point out and this is a hundred percent just an fyi but especially for those of you that go on into chemistry we are going to talk a lot about protons in biology and what they do and so i threw the slide in here just as an fyi that we really don't find protons alone in nature instead they will actually stick to another water molecule making it into a hydronium you do not need to know that for me um this is just if you come across hydroniums you know in the future in your academics you at least have heard of it for the purposes of this class because the active part that we actually care about is that proton itself we will refer to them solely as protons all right so as we saw in the video you can see in water we have an equal amount of hydroxide ions and protons and then we also have some intact water that is not dissociated okay but this would be a ph of 7 because we have equal amounts of both of those okay whereas this example would be hydrochloric acid and you can see when it goes into the water it dissociates into a chlorine ion and our protons and so now we have more protons than we do hydroxide ions therefore this is an acid and then sodium hydroxide when it goes into water it also dissociates so in releasing hydroxide so now you can see we have more hydroxides then we have protons therefore this is a base and overall we can actually see a variety of things that we're used to in everyday life that we find on our ph scale ranging from things that are slightly acidic like coffee and slightly basic like basings baking soda or even milk can be slightly basic as well all the way to the extremes where we find very very rough basic things like liquid drain cleaner and actually some of the dish soap like liquid dish soap that goes into your dishwasher can be very very basic and keep in mind what the goal there is right like the goal of like drano is to dissolve a hairball in your sink and so it's going to have very strong chemistry those charges are going to get in the way of all the bonds and all of the pieces that assemble that hair ball and cause it to come apart or the same idea of dissolving food off of your dishes in the dishwasher and on the far acid side we have battery acid your stomach acid is usually between a ph of one and two and then you know as is like orange juice is usually between two and three so they can be really acidic as well if you've ever heard of using a soda in like a roast or something like that to help tenderize the meat it's actually using the acid component of the soda to help dissolve some of the physical bonds within that meat which is what makes it air quote more tender life in general doesn't exist that far out of that far from neutral and so we have this kind of small window here where life does okay and of course there's extreme examples like there are organisms that live in boiling acid and yellowstone and they do their thing but they couldn't survive in regular water just like most other organisms that are made up of regular water couldn't just survive in boiling acid either so generally we don't see very much life occurring once you get out of kind of the middle area of ph and so just like we saw with water being able to mitigate temperature we also have a variety of compounds that are found within cells that we call buffers and a buffer is actually a combination of a weak acid and a weak base so that they can absorb slight changes in ph your blood is a great example of this so your blood has really good buffering capacity because the carbon dioxide that you breathe actually dissociates into carbonic acid in your blood and so if you get too much co2 in your blood it's going to become too acidic and so your blood kind of mitigates that for a while if you go too far of course then you'll just pass out and then your body will have you start breathing again um but the the slight changes from co2 being released from your muscles until it gets up to your lungs to leave your body your blood is actually able to buffer and so often if you're going to work with cells in the lab you're going to have to use solutions that have buffering capacity just to keep those cells from being damaged by changes in ph we can also look at this at a larger environmental scale as well so things like acid rain where we end up having compounds that go up into the atmosphere and then they dissociate in the water in the atmosphere releasing those protons and then when that precipitation comes back down it brings those protons with which is what we call acid rain and so that actually can drop the ph of soil when you have areas where you have a lot of pollution that is able to come back down and it affects aquatic organisms first so just slight changes in the ph of aquatic environments can do a lot of damage to organisms but even down to a ph of four and so we're talking nowhere near coffee at this point is enough to damage leaves and and kill fish as well and so it's really important for us to be cognizant of altering ph in our environment um even though it is it is a global atmosphere right so there's the potential that pollution released somewhere else can fall down into a different environment in a place where people had no control over it point being though um again that life can't exist too far out of kind of that middle range of ph so in summary for chemistry everything in existence including biological organisms is made up of elements and those elements are able to bond together in different ways we talked about several we talked about covalent and ionic between elements but then we also talked about hydrogen bonds between molecules then we talked about water and its properties that make it so critical for life to exist here on this planet and most of those properties surround the fact that water is polar which again is an unequal sharing of the electrons resulting in a slight negative charge on the oxygen side and slight positive charges on the hydrogen side and then last the ph scale is something that we can use to measure different capacities for compounds to dissociate releasing either a proton or a hydroxide ion and again reminder those two together become water okay so that's it for us for chemistry we will next be looking at much much larger molecules as we start getting into the building blocks of the cell in biochemistry