all right so the last time we talked about periodic table that's where we left off as you go across here you get the periods as you come down here you're going to end up with the um groups now Sadie or Louise do you remember what I said what why do these elements are placed in a group what do they have in common they have a scene a physical and characteristics physical and what else um inner [Music] element chemical yeah chemical chemical characteristics they are the same if you take the period are they the do they have the same physical characteristics or chemical ones they don't why because they are completely different what they do on a period they just go in sequence 19 20 21 22 23 24. okay now let's talk about oops let's talk about the the chemical bonds what are chemical bonds oh what's going on here oh my gosh this is pain whatever I'm just gonna go with this one so what is chemical bond what is a chemical bond basically a bond it's interaction between two elements interaction between two elements it's called a chemical bond now here you see the different types of bonds ionic covalent and hydrogen bond now what is the difference between them ionic involves ions now ions in chemistry it's any element that has charges calcium chlorine if you put these two together you're going to end up with calcium chloride now these two are ions they have positive and negative charges they attract and then they'll form calcium chloride so this is called ionic bond covalent bond covalent bond can be polar and nonpolar now first let's do the non-polar one nonpolar it means that for example chlorine has seven electrons attaches to another chlorine or it binds to another chlorine and they share they share the electrons they share electrons so for covalent they share okay so ionic it's here covalent it's here Now by nonpolar it means that they equally share so they take them at the same time they basically none of them go away or basically none of them goes on go only one side they stick kind of like in the middle now when you talk about the polar one polar covalent bonds hydrogen bond is one of them now here what is going to happen here what is going to happen oh should I still get these things in there oh man I have to keep removing that one and put him back guys sorry I don't know what's going on here but what happens here basically oh by the way this is the this is the ionic bond where you see the ions right there okay this is the ionic bond here you see how this sodium big positive chlorine negative then you have the covalent where there is share equally of the electrons right here in the middle and then the covalent the polar one this is nonpolar this is polar now for Polar if you notice here what it happens for Polar let me see if I have another one right here for Polar what do you notice here you notice that there is also positive and negative charges now where do this positive and negative charges come from this positive and negative charge is here come actually from the electrons they make up the elements oxygen oxygen oops oops let me see never mind oxygen has six electrons foreign has one electron now this element when they are combined to form compounds they like to have eight to be happy at eight so they need to find eight to be happy those eight actually form the complete the complete outside shell or the structure that's when they are complete hydrogen is one of the very few or one of the only that likes only two to be happy now here you see the molecules of water for oxygen to be happy how many electrons it needs to actually kind of gain or get or share since he needs eight to be happy there is two four six that it comes with so it needs two more so then that's why for water you have hydrogen oxygen hydrogen because this oxygen has its electrons right there has its electrons there are six of them plus it gets or it shares because it not really gets it but it shares with hydrogen now when they actually start sharing it doesn't look like this it looks something like this the molecule at an angle now once the molecule it's pushed at this angle right here what happens these extra electrons end up right here at the top on one side and the other side right here the other height the other electron is somewhere here the hydrogen electron is also here so now when you count all the electrons here now oxygen would have how many one two three four five six seven eight now hydrogen by losing the electron when hydrogen loses the electron becomes a proton or positively charged so that's why this positive charge right there that's why this positive charge right there because the electron is pulled towards the oxygen so what's Left Behind it's just a positive charge oxygen uh same thing as the electrons stay right there electrons we learn last time they have negative charge remember protons are positive electrons are negative and neutrons are neutral that's what we learned last time in the in the lecture now here what they form they form a negative Pole and a positive poor by having these poles right here that's why this Bond right here not this bonds sorry this um this Bond right here it's called polar because there is an unequal sharing that's why it's called polar okay any questions any questions all right now let's learn about water and the hydrogen bonding this one right here is called hydrogen bond but it's actually not really hard it's called nonpolar covalent oops this is called non-polar covalent whatever you see the attractions here they are called polar sorry non-non Polar Polar covalent now let's move on to the actual hydrogen bond this is a hydrogen bond right here oops this is a hydrogen bond right here this one right here it's a hydrogen bond this one it's a hydrogen bond now earlier you saw that oxygen had negative charge negative charge and then he had the positive and it had the positive this is a little bit of chemistry here now what happens here this negative charge it's attracted attracted or attract a positive charge from another molecule of water also here this negative charge attracts that's why it's dotted line because attracts another hydrogen as you see right here see how this positive attracts the negative from another molecule so basically these molecules of water because each one is a molecule of water each one of them attracts a bunch of other ones so if you count this molecule or this one how many this one do you think how many molecules of water this one will actually stick to or attract imagine that this this one eventually becomes for the other molecules this one right here in the middle so there's always going to be each molecule of water attracts one two three four molecules of water this is kind of like we move into a class from all of us into a lecture room we hold hands because we are all connected I hold hands with two people then those people that I hold hands with holes with somewhat somebody else with another person now if I want to leave the class what would it happen can I leave the class by myself I can't I need basically to take everybody with me so that's what it happens with water and that's why water flows water flows because of the cohesive property cohesive cohesive it's kind of like we are a cohesive group we are a group that would stick together so this is a cohesive group is that clear okay all right now check out right here these are the properties of water and we're going to go over each one of them fast water attracts other molecule of water so then it's called hydrophilic water does not attract fat water does not attract fat so basically molecules that do not attract the water are called hydrophobic phobia means fear Felix Ophelia means love that's what it comes love and here should have been water afraid now water has all these important properties I already talked about cohesion basically all these molecules of water stick together or cling together through what type of bonds hi hydrogen bonds okay okay now by sticking together that's why water flows when you try to pour water molecules of water they're not going to just flow independently they're just going to stick together water has adhesion properly which basically means that water sticks to other other that's the key word other polar surfaces so that's why sometimes you see the water sticks to for example sometimes to Glass sometimes to plastic because there is parts that are polar Polar means what polar in English it means that it has two poles positive and negative Pole so water when we when we looked at it earlier it was positive had a positive and a negative charge so water adheres to polar surfaces or hydrophilic surfaces so can you guys give me who can give me an example of a polar surface can you guys think of a polar surface something the water sticks to does water stick to salt or salt dissolves in water it does so water and salt uh adhesive part a cardboard a piece of cardboard water actually sticks to it why because there is parts that are polar in that or components or compounds that are polar in the cardboard um napkins water sticks to it why because they put that the type of fiber that they use it's actually has some polar surfaces the next two water has high specific heat and high heat of vaporization now what the heck these things mean high specific heat it means the water absorbs or for water to um absorb sorry for water to evaporate or to turn into Vapors it absorbs or it needs to absorb tremendous amounts of water that's why that's that's the reason like to this weekend is going to be 106 107 degrees we're not going to boil or if you go by the beach the temperatures are way cooler when you go by the beach it's going to be upper 80s why because that water around the beach absorbs the the Heat and it cools down the area around it high heat of vaporization now for water to vaporize requires tremendous amounts of heat for water to turn into vapor so first high specific heat means that water absorbs tremendous amounts of energy before it vaporizes then to vaporize it needs even more energy that's called heat of vaporization the water when it turns solid basically or when it freezes what does it do it expands now water that expands or ice which is the final product floats in water now this is an advantage this is something that's very good because if water or ice would not free when it freezes would not float what would it happen then if you have a lake if you would have a lake like this one right oops if you have a lake like this one right here what was going to happen with the life in the lake it's gonna disappear but since water freezes from the top towards the bottom so you see right there you have this ice layer at the top it insulates the bottoms so then what's gonna happen all these fish here or all these organisms can survive and they can actually slow down and they reproduce for the next spring they prepare for the next spring but anyway lives survives under the ice sheet if if water when it expands or when it sorry when it freezes does not expand and it will not float everything will die in the in the water so this is a very very important property of water now the last one water it's also known as a universal solvent universal solvent Universal means that it's overall so universal solvent in it means that water dissolves almost anything except the nonpolar compounds now non-polar compounds as I mentioned earlier one of them is actually oil oil does not mix with water oil is polar but sorry non-polar oil is nonpolar and water is polar oops let me clear everything all right now quickly acids and bases what is that acid and basis an acid it's something that it's a little bit sour a base it's a little bit sweeter now what does it give acidity what it gives basicity if it's an acid you have a lot of hydrogen ions this is an asset if it's an hydroxide ion hydroxide ion it's going to be a base now basically acids have high hydrogen concentration and you can see right here oops you could see right here and bases have low hydrogen concentration or high hydroxyl hydroxyl ion or hydroxide ion concentrations and this leads us to the pH scale now what's pH scale pH scale it's basically as the name implies it shows the hydrogen ion concentration the more hydrogen ions you have more hydrogen ions you have it's going to be more acidic or an acid less hydrogen ions is going to be a base now when you look right here on this scale you can see hydrogen concentration 10 to the zero it's very high versus 10 to the negative 14. how much is 10 to the zero 10 to the 0 is 1 10 to the negative 14 is how much point zero zero zero zero zero a bunch of zero till the 14th one so when you look right here anything that is 10 to the negative 14 it's way less acidic than the one that's at 10 to the zero now here you can see the two of the strongest acids and bases that we use in chemistry hydrochloric acid and Hydrox sodium hydroxide we're going to use this one through our lab so please remember that sodium hydroxide is what is it a base or an acid base hydrochloric acid that doesn't mean tells you it's an acid right there okay now between 0 and 14 which is the pH scale the strongest acid the strongest base right here you have a bunch of other numbers the sequence one through four zero through 14 is the pH scale now at seven or in the middle at pH 7 a pH 7 we have actually Neutron neutral neutral okay this is neutral so water it's neither base neither acid it's neutral urine when you pee actually urine it's slightly acidic coffee when you drink coffee you all know this one if you drink coffee it's slightly or a little bit acidic tomatoes and tomato juice it's actually actually acidic lemon juice it's very acidic stomach acid it's very acidic it's about pH too as you go the other way seawater when you go to the ocean sea water it's not sour because it's a base it's a very weak base it's about pH eight baking soda it's the actual it's a buffer and we're gonna go in a minute over it it's a buffer household ammonia why do we use household ammonia any of you can tell me what use household ammonia for to clean grease around your stove if you read on it all those products that are used to clean the grease on your stove actually contain ammonia household bleach that is actually very strong base so when you look right here actually bleach it's a base it's not an acid a lot of you a lot of students believe that bleach is an acid but it's not it's actually a strong base all right now here as I mentioned earlier we talked about we talked about buffers what is a buffer a buffer it's basically a substance or it's actually a substance it's not really a compound it's a substance that it's made and it has one interesting ability it has the ability to keep the pH stable pH stable means what it means that it if you add acid or if you add base to this solution it does not change or very slightly will change its pH so buffers by definition this is the keyword resist resist changes in PH how by taking up the hydrogen ion or the hydroxide ion from the solution and basically they are pretty stable here you see my Lantern as I mentioned earlier baking soda baking soda or or the oops or the sodium bicarbonate it's a buffer now when you have um stomach acid what you can do you don't have to to take Mylanta you just put some baking soda in water you mix it yes it doesn't have that nice flavor that you would find probably in Mylanta or Pepto-Bismol but you take it and it has exactly the same effect effect as Mylanta or as the Pepto-Bismol so I hope you guys understood so far whatever we've done now the last one this is the interesting part the cool part application buffers and pH application here you see what you see a forest now this Forest is all destroyed why because of the acid rains now how can you meet mitigate this process of acid rains you can just go and spread a bunch of buffers on these leaves because you don't have the time and you don't have the resources so what do you do then you just have to basically remove the source of producing of a source of uh the source of the chemical required to form the acid rains in this case it's going to be the power plants power plants relates release a lot of sodium non-sodium sorry sulfur trioxide nitrogen dioxide sulfur dioxide they release into the air and then this combines with water all of them combine with water and they turn into acid oh sorry acid rain now here you have a starch this is much easier to mitigate the process this starch if you look right here has a bunch of holes in it right there now what is why is that because of the same reason acid rains or the acidity over time now how can I mitigate this one pretty simple pretty straightforward I'm just going to go and grab a buffer and I'm just going to apply it in top the buffer or everywhere and then what's going to happen that buffer takes up the acid and then the acid what is it going to do it's going to be neutralized it's going to be neutralized now you've probably seen this one when you guys go to get a museum or you would go to museums like really fancy museums uh if you go there you're going to notice that every painting in top has a layer of buffer why do you think that those paintings have a layers of buffers in top because when you go to the museum me you whoever it is a person gets really close to it and once it gets really close what's going to happen it's not going to spit on the on the on the painting but what it does is you actually uh breathe you produce carbon dioxide carbon dioxide mixes with moisture from the air and turns into Carbonic acid which is an acid that has the ability to corrode or to destroy the painting now if you put a buffer in top if you put a buffer in top as you see right here one of oops one of these ones here one of these buffers in top one of these buffers actually if you put it oops not there this one here if you put one of these buffers in top you can actually protect the the painting so buffers are very important because buffer have the ability to resist change have the ability to resist change in pH okey-doke any questions all right so now what I want you guys to do I want you guys to actually look at this part right here oops and try to fill it in also this is some simple exam question now this is if you were in class these are very easy for online so I'm gonna ask something that it's way I mean no way but a little bit harder than this one so you can go over these questions here that I posted and if you cannot solve or you cannot answer this question in less than 30 seconds then you need to actually read more same thing right here same thing right here same thing right here and right here all right so let's see Since There is five of you let's go with the first question so let's see Priscilla tell me the first one the answer so it's going to be a oops all of them are going to be something like this A B C D or E whichever one it is so which one is for this one pretty soon fast uh is it a a no it's actually C electrons electrons move around the nucleus Luis number two remember these are very simple questions that these are for in class exam not for online is eight eight eight good Candace what's this Milan you're gonna be next is a day the same numbers of protons and neutrons no it's actually C they have the same chemical properties but differ in atomic mass because the atomic mass is different because the Isotopes if you were here if you have you guys read please those lectures that I gave you Isotopes have different atomic masses because they have different number of neutrons they have different number of neutrons so they cannot be they cannot be D canvas because they don't have the same number of protons and neutrons protons stay the same but neutrons do not stay the same okay I get it so when you look right here let me go fast back oops right here you see what is you see carbon 12 13 and 14 12 13 and 14 is the atomic mass and if you look all of them have the same number of protons do they have the same number of neutrons we have six seven and eight they have the same number of electrons but not the same number of protons okay all right now the next one is going to be Milani okay Milani are you still here with us Milani Milani yeah you are can you talk or you can't talk oops sorry so here's the question so tell me on the chart which one do you think it is and I'll and I'll say it loud foreign sorry I didn't see it oh I can't see the chart for some reason no uh D let's see a chemical compound consists of no it's not D it is B two or more elements combined in a definite proportion so compound is two or more it's not three or more okay what happened Louise nothing okay hydrogen bonds are the result of who can tell me you got it Milani so hydrogen bonds are the result of what any of you tell me foreign what do you think Priscilla what do you think I'm thinking C C how about you Priscilla um I'm thinking possibly B so check this one out here this is the hydrogen bond that we're talking about earlier you see right there so is it just the molecules colliding that's what forms hydrogen bond yes no is there three or more what was the answer what was the question right there sorry I forgot it an example the bonding of different is are these isotopes are these isotopes no because Isotopes would be what it's an element that has different neutrons so it's not Isotopes so what would it be when you look right there it's basically the unequal sharing of electrons you see right here I talked about it this unequal sharing of electrons that takes place right here gives the rise to these positives and negatives right there this unequal sharing unequal sharing gives positive to negative at the top positive adder the bottom and then what's going to happen what is going to happen next right here oops what's going to happen here you get these molecules that attract to form the hydrogen bond is that clear any questions all right so I think that that's all what I'm going to do for today and I can pick up the organic chemistry next week so what I'll do next week I'll have two lectures one Wednesday and I'll try to have on Monday too but Monday is the um labor weekend so it doesn't really matter you know I told you you don't have to attend them because I'm gonna post the actual lectures uh through zoom and make sure and I'm repeating and that's the last time when I repeat make sure you download them if you want to have the lectures because that link is going to be valid or available only for about a month I think Zoom set so yes you have to get a hard drive and you have to download it okie doke okay I I mean it's your responsibility guys to do that yes I can download them on canvas but then I have to delete them or add more or less you know what I mean because I have to keep replacing so I do exactly the same the same thing but I give you the access to download can you guys download can you check any of you if you can download the previous link that I send you there got to be a function there where you have to download because you should be able to download the actual recording on the link yeah it's up in the upper right pruner but you can download it right yes thank you Candice so that's what you guys should do so you guys you guys gotta have a computer or a hard drive or something that can store that much like whatever by the end of the semester we're gonna have like probably like four or five gigs of gigabytes of it so you need to have some of those if you need to look at them okay any questions all right I'm going to stop the recording now since we're done