[Music] hi it's Mr Anderson and this is chemistry Essentials Video 17 it's on dipole forces before we talk about dipole forces we should probably identify what a dipole is water is a great example of one we have one oxygen and two hydrogens and since oxygen is highly electr negative it's going to pull the electrons towards it and so it's going to have partial positive charges where the hydrogen is and partial negative charges where the oxygen is and so it's a dipole what does that mean is we have if we ever have separation between the positive and negative charges we've created a dipole from the positive to the negative and so dipole forces are going to usually occur when we have at least one polar molecule and so that's called a dipole it's going to have partial charges positive and negative and so we can have a dipole force between a dipole and a dipole so it's called a dipole dipole Force we can use diagrams to figure out how they're going to orient themselves and the most most famous one is called hydrogen bonds hydrogen bonds are going to form when we have hydrogen bonded either oxygen nitrogen or Florine and it creates a dipole it's going to hold molecules together we could also have an attraction between a dipole and an induced dipole this is something that's not polar but can be for just a second the strength of this uh force between the two is going to be based on the polarizability in other words how much we can make that turn into a dipole and then the magnitude magnitude of the original dipole and then finally we can have a force between a dipole and an ion this is going to be really important when we're using dipoles to break down Solutions an example would be water breaking down salt and so before we get into dipoles make sure you understand the difference between intermolecular and intr molecular intermolecular is going to be between molecules like Interstate goes between states and so the force between this one molecule of hydrochloric acid and this one is going to be an intermolecular intr molecular is going to be the Cove valent bond between the chlorine and the hyd hydrogen likewise we could have water around Salt they're going to have a ionic bond between the chlorine and the sodium ions but it would be an intermolecular between the water and the ions themselves also this helps explain the difference between real and ideal gases remember ideal gases are just theoretical but as the as the gases become closer to liquid as they start to condense we're going to start to have attractive forces and some of these are going to be dipole dipole forces so let's look at a specific dipole let's say we have hydrochloric acid hydrochloric acid is going to have one atom of hydrogen and one of chlorine chlorine is going to pull that electron towards itself and so it's going to have a partial positive and negative charge positive is going to be where the hydrogen is negative is going to be where the chlorine is and so if we have two of these what we'll get is a dipole dipole Force it's simply a force between the two dipoles and it's going to hold hydrochloric acid together so if I had a bunch of hydrochloric acid molecules and I put them like this they could never exist like this but let's say I put them like that with all their negatives on the inside and positives on the outside how do you think they would Orient themselves well it would be something like this they're going to orient themselves so we have a negative to a positive to a negative to a positive to a negative to a positive so imagine in hydrochloric acid we have all these interconnections going on now a specific type of dipole dipole is going to be a hydrogen bond hydrogen bonds are going to occur lots of people think it's between hydrogen and something else it's not that so hydrogen bond is going to be occur when we have hydrogen bonded to either a nitrogen oxygen or a Florine and so in water we have hydrogen bonded to oxygen so when it does that we're going to have unequal sharing and so we're going to have a dipole we're going to have negative side where the oxygen is and a positive side where the hydrogen in now let me show you where the hydrogen bond is this is how water would really Orient itself this is going to be a hydrogen bond right here between the hydrogen and the oxygen of an adjacent molecule or between this hydrogen and this oxygen of this adjacent molecule and hydrogen bonds are incredibly important and they allow small molecules like water to have pretty good bonds that hold them together in fact that's why it's really hard to change the temperature of water it has a high specific heat it's due to these hydrogen bonds but we could find it in larger molecules as well so if we're looking at the nitrogenous bases these are the bases on the inside of DNA this ladder what's holding them together are going to be these hydrogen bonds hydrogen bonds are holding it it's between the hydrogen and ox oxygen or hydrogen and nitrogen of the another molecule and so hydrogen bonds are incredibly important but again they're dipole dipole we could also have a dipole induced dipole Force okay what's this going to be it's going to be between a polar molecule and something that has no charge at all well something that has no charge and Noble gas is an example of that so let's say we have hydrochloric acid molecule next to argon argon remember is going to have no charge all the electrons are equally distributed well as it comes closer Watch What Happens as argon approaches hydrochloric acid some of those electrons in its surface are going to be attracted towards this positive charge of the hydrogen and as a result what we're going to create is a temporary dipole or an instantaneous dipole so it just happens for a fraction in time but now we have this Force holding them together a force between the dipole and an induced dipole now what's going to increase the ability to be induced well it's going to be the strength of this dipole the more strength there is in that polarity the more likely we are to induce dipoles and then the other thing is going to be the polarizability of that other atom or other molecule the more electrons it has the more likely those electrons can be tugged on and we can make these instantaneous dipoles and then finally we could have an attraction between a dipole and an ion and so a great example of this is how water dissolves salt they're going to be huge bonds intermolecular between the chloride and the sodium ions and that's why salt has this beautiful crystallin structure but you know if we add it to water we can quickly break it down and can form a solution well what's going on there we have a chlorine ion and then we have a sodium ion and what's going to happen is the water will Orient like this around that chloride ion and so we're going to have the positive ends of the water attracted to the negative ends of the ion if we look at the sodium we're going to have the negative parts of the water attracted to the positive parts of the sodium and so what they're really doing is kind of ushering these ions away from that original ionic compound what happens if we remove the water then those ionic compounds come back again and we get that sodium chloride so did you learn the following that we could relate the real gas behavior to some of these intermolecular remember as a gas gets closer to condensation we're going to have more of these attractive intermolecular forces did you learn to relate the feature of a polar molecule to the attraction between them remember this diagram shows that got two dipoles and you could probably turn it so you could Orient it the correct way and then finally could we use kum's law to explain why dipoles are attracted to ions remember all it has to do is those partial charges of the dipole in this case water attracted to the ionic charges or the ions and so that's going to allow them to dissolve it and it's simply colum's law that attracting between positive and negative and I hope that was [Music] helpful oh