hey guys it's michael from chemistry in today's video we'll be talking about how to determine which imf or intermolecular force a substance has let's start with the definition of imf intermolecular force is defined as the attraction between molecules for example i have two water molecules right here the attraction between one water molecule and another water molecule is called the intermolecular force that's in contrast with the the bonds between the o and h these right here these are bonds they're covalent bonds these are called intramolecular forces or just bonds so intermolecular forces are attraction between molecules and that's different from the attraction within the molecules or the bonds the three main intermolecular forces that you'll need to know in most chemistry classes are blend dispersion force dipole-dipole and hydrogen bond so how do you determine which of these forces a compound will have well you can just use the skyline if a compound is nonpolar then it will have london dispersion forces only if a compound is polar it will have lung dispersion and dipole dipole and then lastly if you have a compound with h that's directly attached to an f a h directly attached to o or h directly attached to the n then we'll have all three have one dispersion dipole dipole and hydrogen bonding so everything all compounds have one dispersion if it's polar it'll also have the hypotypo and then if it has hf h or hn they don't have dipole dipole and hydrogen bonding so let's take a look at some example problems and apply these rules in this problem we have to determine what imfs are present in the following substances the first substance is carbon dioxide to do this we first have to determine if the compound is polar or nonpolar and to do that you have to draw the lewis structure so to i'm just going to draw the lewis structure to save time but if you're having trouble drawing lewis structure check out the video in the description below where i'd go over that in detail the lewis structure for carbon dioxide looks like this c with double bond and then each of the o's have two lone pairs then we have to check whether this compound is polar or nonpolar and to that we can just use a quick checklist i have a video where i go over this in detail but for sake of saving time i'm going to type out this checklist right here so compound will be nonpolar if the central atom the middle atom has no lone pairs and all the atoms surrounding the central atom are the same you can see carbon meets criteria number one because carbon doesn't have any any lone pairs on it and it also meets carb criteria number two because both surrounding atoms are oxygen so that means that carbon dioxide will be nonpolar and since it's non-polar it means that it only has london dispersion forces so we'll start once again with the lewis structure and the lewis structure sf4 looks as such then we need to determine whether this molecule is polar or nonpolar so we use the checklist we see if the central atom has any lone pairs and s does have a lone pair on the center atom so since it doesn't meet this first criteria then i mean this compound is going to be polar and since it's polar it will have lung dispersion forces and dipole dipole it doesn't have hydrogen bonding because we don't see any hf h or h n in this in this compound okay next next example ch3 nh2 just right off the bat we see that there's n and h right next to each other so that means this compound meets it has an nnh which means it's going to have land dispersion dipole dipole and hydromonin so if you see hf h0 or hn in the molecule then you know it's going to have all three next example c5h12 here's a here's a neat trick so any compound containing carbon and hydrogen only is going to be nonpolar so since c5h12 only has carbon hydrogens it's going to be nonpolar which means it will have lung dispersion forces only other examples of this be like c c4h10 c20h40 so any compound that just has carbon hydrogen will be nonpolar meaning it will only have one dispersion forces next example neon this is a single atom a single element so if it's a single element then it has to be nonpolar and since it's nonpolar it will only have london dispersion forces only for neon and then lastly hcl now we draw the lewis structure for hcl it looks like this and we know that cl is more electronegative than h which means that you're going to have a dipole moment pointing in this direction and so that makes it polar and if it's polar it will have lung dispersion forces and dipole dipole but it doesn't have hydrogen bonding because we don't see hf h0 or hn and that's how you can determine what type of intermolecular force a substance has the first step is just to draw the lewis structure then determine if it's polar or nonpolar so once again i went over that pretty quickly to save time but i have videos that teach you how to draw loose structures and determine if it's polar or nonpolar in detail and if a compound has hf ho or hn then that means that's hydrogen bonding dipole dipole and lend dispersion force if you want to learn how to ace chemistry if you want to learn what's the best way to study for this class if you want to learn some neat tricks and tips to take into your exam and do better on them then you should head over to my website and get this free guide 12 secrets to ace and chemistry you can head over to www.conquerchemistry.com i'm going to include a link in the description below check it out i think it's really going to help you and you're going to you're going to like it until next time keep working hard and continue the good work