and I grade 11 so we continue with chemical bonding and today we're doing intermolecular forces today there will just be an introduction very important with tensions in your notes were on page 17 so I hope you found an updated version of the notes on Google classroom I hope you can print them please please make every effort to try and print the notes and I'm going to talk about today so we've been focusing on intra molecular forces or bonding we've been dealing with bonding types we've worked with covalent bonds ionic bonds polar covalent bonds nonpolar covalent bonds even metallic bonding and we know that this is about bonding between atoms and it's yeah we've spent a lot of time on it but now we're interested in something a little bit different and that is inter molecular forces let's have a look at what it's about so on page 17 you've got this introduction and the introduction is going to give you the definition and some importance of what intermolecular forces is all about so it says the section describes the different types of forces between molecules alright this type of force is different to covalent and ionic bonding which occurs between atoms and is therefore called intra molecular forces here we're interested in the force between molecules the definition make sure you know it well define intermolecular force as a weak force of attraction between molecules ions or atoms of noble gases so there's many different options and we'll go through all the types but the main most important thing is that a weak force of attraction that happens between the particles alright between particles such as molecules ions atoms of noble okay so intermolecular forces are weaker than intramolecular inter-atomic forces so our intermolecular forces which will give them names etc but they are much weaker than our covalent bonds or our ionic bonds okay this means that less energy is needed to separate the molecules then CH break the part will elaborate on that energy is important in this topic and it's important to identify whether we have strong intermolecular forces or weak intermolecular forces when intramolecular forces are broken the chemical properties of the substance will change new substances will form look at the image on the right hand side of the screen you are seeing at the top water molecules to HQ oh and what are we doing here we are chemically changing them into hydrogen and oxygen gas yeah inter atomic forces are broken come in water in order to make totally new substances totally new gasses and molecules so here it is an inter atomic attraction which is broken by the use of energy okay but in the section now from this page onwards were interested not in inter atomic or intra molecular attraction or forces were interested in inter molecular and it says when intermolecular forces are separated the resistances does not change but the phrase of the substance will change in look at the image on the right hand side you are seeing water molecules again and first you know they're really quite close to each other the attraction between them is strong and on the right hand side of the arrow you're still seeing water molecules because I have not chemically changed water all I'm doing to the water molecules is I am separating them and this really tells you that this entire the section are we going to be looking at now is going to be focusing on the phases of other substances so we're going to be interested on whether a substance is a solid and liquid or a gas we're going to be interested in how much energy is needed to change your substance from a solid to liquid to a gas we're going to be very interested in the type of attraction that exists between the molecules or the atoms or the ions in order to make it a solid is it a strong attraction is it a weak one we're going to classify the type of intermolecular attraction that's gonna determine the phase of the substance okay so here you've got three three those are all images water on the left-hand side as a solid then in the middle as a liquid and then on the right as a gas and if you look at the solid water there has to be an attraction between neighboring water molecules for them to sort of in inverted commas stick together just state it together to form those ice molecules there has to be an attraction and that makes it a solid that attraction between those molecules is called an intermolecular force and that's what makes it a solid what are you gonna do to have to turn it into a liquid why you and I have to apply energy and so you're gonna apply energy that energy is gonna weak of that attraction that exists between those molecules and it's gonna loosen that attraction and it's going to give you a liquid you applied with more energy you heat it up a little bit more and it's going to turn into a gas now I found an animation which is able to show you this in you know on a molecular and atomic level and so it's been a bit of time looking at that animation here we have an animation which is going to help us understand our intermolecular forces I remember intermolecular forces are defined as a weak force of attraction between molecules ions or atoms of noble gases so I'm going to show you three substances and you know work through the terminology that we use in intermolecular forces so yeah I have two selected oxygen first so those are oxygen molecules you can see they're diatomic and they're in my container at a temperature of minus 240 degree Celsius it's pretty cold you see they're shivering there they've got very little energy but they're really quite tightly packed and the fact that I tightly packed tells me there's a force of attraction keeping them together they're attracting each other enough to give you the solid so what do I need to do to try and turn them into a liquid and eventually into a gas well I need to apply some heat so let's apply a little bit of heat okay they're moving a little bit faster they're warming up and as they're they're warming up than they're moving a little bit faster the energy that are supplied is being absorbed by the molecules and those molecules are vibrating or moving a little bit faster some cases they're moving and vibrating so fast that is overcoming that attraction between the molecules and that attraction between the molecules is really weakening and that means they're able to move a little bit easily over each other and able to flow around each other giving us this liquid let's warm it up a little bit more and you'll see that they'll vibrate a little bit faster and again flow over each other with more ease and that means I'm overcoming the attraction between the molecules and I have melted my oxygen solid what if I keep applying some heat so I keep applying some heat warm them up and what do you noticing some of the molecules are doing well some of the molecules aren't totally moving away they'd escaped they've totally been separated from the other molecules and that means you've applied enough energy to actually overcome the intermolecular forces and your your substances you know is boiling you've turned it from a liquid to a gas you can see in this case that this is still at an incredibly low temperature of minus 187 degrees Celsius that means I didn't need to apply a huge amount of energy or heat to separate those intermolecular forces the next substance I'd like to show you would be a simulation with neon so this is neon gas remember neon is a noble gas it is made up of atoms and so remember our definition for intermolecular forces is weak force of attraction between molecules but also between atoms of a noble gas so these atoms are in the solid phase at the moment that means there must be some form attraction between these atoms that causes them to stay close to each other and stay in the solid phase now this is again at an incredibly low temperature of minus journal 59 degrees Celsius what if I decide to heat it up a little bit well those atoms are not absorbing some of the energy and they are moving and flowing a little bit more easily over each other and that means that that attraction that little molecular attraction between the atoms has really been overcome and it's turning into a liquid since of them are escaping already and really with a little bit more heat I would have all of them moving around and and turning into a gas but note that the temperature at which this happens it's very very low now that's gonna tell us something important about the attraction between those atoms at the moment they're all in the gas phase at minus 230 degrees Celsius that's incredibly cold and that means that it need a lot of energy to separate to separate the atoms from each other one more example so the last example in the simulation I'm going to use is going to be water so those are water molecules in the solid phase you can see they're quite far apart but that's actually how they exist in the solid phase which in some way explains why ice floats but that's a conversation for another day but so those water molecules are in the solid phase at the moment you can see it's pretty cold at minus 127 degrees Celsius but there's solid that means there is an attraction between those molecules those molecules are attracting each other there are intermolecular forces between each of them and I apply some heat watch the temperature and of course watch what those molecules are doing I've gone up to minus 65 degrees Celsius they're still in the solid phase I heat them up a bit more oops and I go to zero degrees Celsius let's go just a little bit above zero it's got a four degrees now here they're actually in the liquid phase these these molecules are now no longer in the solid phase they're in the liquid phase we've got water at four degrees that means we've overcome some of the intermolecular attraction next I'm gonna heat it up now we know that it's gonna turn into a guest at a hundred degrees Celsius so let's let's update a little bit at this point I don't know if it's animations exactly at a hundred so we might have to a little bit higher some of them look at them go so here we can see that some of them are totally broken 334 degrees Celsius and that's because I've applied so much energy that they're no longer attracting each other the energy that they had is too much for the attraction between neighboring molecules and so they've turned into wonderful okay now what I'd like us to do is think while water boils and melts at much higher temperatures than what we saw for oxygen and neon let's go back and look at so getting back to the oxygen one remember - 239° it's still a solid I heat this up a little bit more and I want to notice what what temperature it's really going to turn into a liquid am I going to be able to melt it or I think I'm about there and that's minus 209 degrees so low that tells me I have to supply so little energy to overcome those attractions so this is going to be important to us the point at which something melts or boils is going to help us identify whether the forces of attraction between molecules or atoms are going to be strong or weak all right and from this animation hopefully you've seen that the attraction between water molecules is much stronger which is why I need to apply so much more energy and get you a much higher temperature to be able to melt it and boil it for oxygen and even for the neon that we did earlier on I don't need to add a lot of energy and it's already a liquid or let's add a little bit more and what's gonna happen to those molecules they're going to be turning into gas pretty soon all right so and that means the force of attraction between them is incredibly low and that in the structure is going to be one of the most important things it's gonna be about comparing I am the boiling points of substances to identify whether they have weak or strong intermolecular forces and vais hope that animation was clear and and made you understand that we're going to be interested in boiling points and melting points the energy required to overcome the attraction between atoms or molecules or ions to overcome the intermolecular forces of attraction and obviously not all substances will have the same intermolecular forces because not all substances melt or boil at the same temperature so on page 17 you have this block or at the cell table which shows you four substances you go water and it tells you the boiling point of water is 100 degrees Celsius hydrogen chloride boiling point is negative 85 degrees Celsius and fluorine a - 188 degrees Celsius and helium - 269 degrees Celsius a vastly different boiling points for these four substances and so why are they so vastly different and there's a lot of what we've learned so far in the subject that's gonna help us to understand that you already can look at these four substances and hopefully tell me whether they're what type of bonding is involved in these in these molecules you can tell me the the shape of the molecules you can probably tell me of the molecules polar or nonpolar all right so that will be useful in what we're going to do next okay so we're gonna pause I'm gonna give you a moment to just jot down in the block what it is so far that you can tell me about these molecules and then we'll talk about the intermolecular forces okay so hopefully you've given this some salt and you realized okay water is an angular molecule it is a polar covalent or polar molecule with polar covalent bonds hydrogen chloride a linear molecule with polar covalent bonds and if was a polar molecule fluorine is a linear molecule but it is diatomic and therefore there's nonpolar covalent bonds and then there's a non-polar molecule helium well actually II liam is not involved in bonding it's just gonna be atoms remember helium is a noble gas alright so what we can see here is that they each quite unique in their shape and their type of molecules are there and that's going to be useful in determining the the the melting point and boiling point see here we can see it has the highest back so here we can see it has gone for some reason that doesn't want to right it's all right below this is the highest boiling point and you can see that that boiling point is decreasing to the lowest boiling point here what does that tell you well this is going to tell me that this is going to need a lot of energy is required to overcome the attraction between the molecules whereas here very little energy is going to be required to overcome that attraction and this is going to tell me here very importantly that this is going to have strong intermolecular forces for us as I go down these are going to be very weak intermolecular forces and that part is obviously what we are focusing on here understanding that the boiling point of a substance is going to tell us whether the attraction between the molecules or the atoms of that substance whether that attraction is very strong or whether it's very weak all right and this how are we going to determine whether the force is strong in a week well we are going to spend quite a bit of time identifying intermolecular forces is going to be dependent a lot on the polarity of the molecules okay so this is just an intro I'm then going to talk to you briefly about the types of intermolecular forces that we're going to deal with and you can see there here that on page 18 of your notes and the weak forces of attraction are known as von der Waals forces those are the names of our intermolecular forces after this gentleman mr. JD front of all and there are three types front of us forces that we're going to learn in grade 11 so that only three we need to know the first one we're gonna study is going to be called momentary dipole induced dipole forces or London forces so it's quite a mouthful we can call them London forces but we have to understand why it's got this name of momentary typo and use dipole that's going to be the next video then B will be dipole dipole forces and then C will be hydrogen bonds so going back to this table by the end of this topic you should be able to tell me that water is hydrogen bonds that helium is going to be moment a typo induce dipole etc we will be able to identify the type of intermolecular forces on a substance and that's going to use our knowledge of the polarity of molecules it's going to use our knowledge of of yeah boiling points and indication of intermolecular forces okay so that's our intro for this topic we will wait for another video to see the rest thanks everybody you