what we will be looking at today is the next part of 4.40 materials and in particular it's just going to be looking at metals and I think part of it really is focusing on the production of metals and and looking at what methods are used based on aspects around their reactivity so we start here looking at the occurrence of metals in combined or uncombined form in the Earth's crust and how that's related to reactivity and something that you would need to be able to do is given the position of the metal in the Activity series and that's something that will be given to you in an exam you'll have to be able to predict whether the metal is likely to occur in nature in a combined or uncombined form so it's a fairly straightforward thing to do but really the important thing is looking at what we can do in order to make metals given their different reactivities so from this particular slide it does cover some ideas that would have been covered in stage one and in particular you can see here in subtopic 5.2 I believe or was it 6.2 I think it was actually 6.2 and it was really to do with metals and their reactivity going back to our work on redox that we know that metals are substances or elements that typically lose electrons another way of saying that is that metals undergo oxidation reactions or half reactions which does mean that they have this tendency to lose electrons and so basically the more reactive we say a metal is the greater their tendency of being able to oxidize or to lose electrons as means of becoming stable if it is undergoing oxidation it means it is causing something else to become reduced that is to gain electrons so we could talk about a metals ability to act as a reducing agent this particular slide is looking just at this combined uncombined idea that we know that certain metal typically can only be found combined in nature so sodium aluminium iron zinc you've got some different forms of those different elements in a compound form also referred to as a combined form a lot of these for example might be found in ores which we then have to mine we have to process and then we have to find a way to actually form the metal from those compound forms where as we know that there are metals that are much less reactive or active like gold platinum silver and in these cases there is a good chance that you could actually you know find some perhaps in the ground and actually be able to find pure samples of it so coming back to this idea of reactivity I'm hoping that you all remember seeing what we call a metal reactivity series in some form but it essentially just lists the metals in order of their increasing or I should say decreasing reactivity actually because at the top of your series you've got the most reactive metals and then that just follows on down the bottom to where you have the less reactive metals it doesn't include every single metal that we're aware of but it typically includes any metals of relevance to us and metals that we are typically going to actually find especially in the Earth's crust this is something resembling a metal reactivity series but it does include some additional information the important thing is just being able to see the metals from being most reactive up the top or most active going down to the bottom to your least active this can vary a little bit depending on what source that you have as well but I've decided here that you have your most active followed by your least active down the bottom here and something else just to kind of keep an eye out for is hydrogen knowing it obviously isn't a metal but we typically look at putting it in as a comparison it's used in this case to see how its ability to I guess undergo oxidation and its reactivity can differ compared to the metals and another one that we might commonly see would be carbon and what I'll actually have put in is water and that will become quite apparent as to why I put in water but just to sum up what we've actually seen previously we do find quite a lot of these metals that will typically be found combined in nature typically your silver mercury and so on you should be able to find as just three elements in nature okay so we'll just move on to the next understanding then and this is looking at the process of being able to reduce metals so we have the method used in the reduction stage in the production of the metal is related to its reactivity as well as the availability of energy and so knowing that you do have a metal activity series given to you in exams and tests you would have to be able to predict and explain what the likely method of production is for those metal compounds and that can include a number of different processes we're actually going to focus on electrolysis just in general I'll go through some more specifics and some more specific examples of metal production processes in the next video as well as also looking at just simply using reducing agents like carbon as a way of reducing metals as a little bit of a reminder so again just from last year we learnt this acronym which helps us understand about the different halves of redox knowing that we have oxidation and reduction if we're talking about metal production this is what we're really focusing on is the ability for metals you know combine form to gain electrons and turn from possibly ions into metal elements but for that to happen you would need something to undergo oxidation that is to lose its electrons to the metal in its combined form so to just summarize some of that information we know metals and combined form will consist of metal ions those ions can gain electrons and form metals in their elemental form so how this actually is done in the industry depends on obviously its reactivity but it also depends on what the energy demands are needed for these different processes and I guess a bottom line is that you want to try and expend or use only as much energy as you need to in order to produce that metal so from here I've just added another point so you can see in blue here I've just put this decreasing ease of reduction which is kind of the opposite of this statement here where it's talking about there increasing ease of oxidation so going from the bottom to the top lithium is the most likely it's going to be able to undergo oxidation the most readily in this set of metals but if we also look at that same trend it means that the ability to produce the ions in a compound form will be I guess much more difficult down the bottom here if we were to have say gold in the inner compound form it would be very very easy to actually allow for reduction of it in order to form gold metal so from there we can actually break this down into some of the key waves we undergo reduction for metals and so if we look at our most reactive metals what we find is that we carry out a process called electrolysis of a melt it's a liquid version of an ionic compound essentially so these being in a compound form we would need to heat them to a point where they do become melted and then carry out electrolysis of that you can imagine that could take large amounts of energy and we'll talk more about that later if we get to your less reactive zinc down here then we can actually carry our electrolysis in aqueous solution you can see I've popped in water in this series even though it's not a metal it's not even an element and that's because water actually has an ability to undergo redox reactions as well so water we know actually can undergo reduction itself and anything essentially above water won't be reduced if water is present because water will be more readily reduced from that point we can actually look at reduction using less energy intensive processes so that could mean using substances like carbon or carbon monoxide they act as reducing agents meaning that they cause reduction or they cause the gain of electrons of metal ions into metal elements and we also know again that a number of these just won't be found combined generally speaking so we don't really need to consider methods of reduction for them let's now go into some more detail about electrolytic cells so this is probably the first time that we've covered it in in chemistry we know that electrolytic cells are used to produce required substances and that could be not just metals but other things what we need to be able to do is identify the anode and cathode like with a galvanic cell as well as their charges and also the direction of ion and electron flow given enough information the other thing we also need to do is be able to write a lecture at half equations for an electrolytic cell again if we're given enough information what is electrolysis so we could define as a process of using electrical energy or an electrical current to cause a redox reaction that typically doesn't occur spontaneously in other words we could say it is the conversion of electrical energy into chemical potential energy because we are going to form products that will hold that energy and then those products could potentially be used as reactants to then do the opposite so we do that through electrolytic cells in terms of applications obviously we will look at active metal production electroplating is something that you might have come across but that typically involves the coating of one metal on top of usually another metal or of another substance and that's usually used as a form protection so an example would be something like galvanizing which involves using zinc as a protective layer over other metals like steel and the thing with zinc is knowing it is quite reactive it does form a relatively impenetrable cur os-- corroded or zinc oxide layer which then stops the inside components from actually undergoing corrosion and oxidation the other way that we could actually use is in the production not just of metals but nonmetals so we could think for example hydrogen for possibly hydrogen fuel cells and their production it could be in terms of the harbour process although there are other processes for that chlorine for water treatment water disinfection so you can see that there are other applications behind electrolysis so this diagram I'm going to use just to help summarize how electrolysis takes place and I just want you guys to try and follow along as best as you can chances are you got a diagram that would would have been quite similar to this so what I'll do is I'll break down each of the parts and we'll talk about what they're responsible for and and what actually happens electrolytic cell I'm going to start up the top here this is different to a galvanic cell that uses redox reactions to generate an electrical current in the case of an electrolytic cell we need to put in energy in the form of electrical energy so up the top here we have some type of power supply that is going to act like a pump and allow for electrons to be pushed through an external circuit so let's start from here then we've got our power supply this is going to push electrons and this shorter end is what we refer to as the negative terminal so the negative terminal is where we get our initial flow of electrons flows down to this electrode here this is what we call the cathode because what we're going to get is the process of reduction occurring we also give it a negative charge knowing that we have deposited electrons and negative charge onto this electrode what will then follow on to look at is what's happening in this liquid component what we call our electrolyte and so what you can imagine is that we have metal ions that can freely move so that they're mobile they're going to be drawn to or be attracted to this source of negative charge so positively charged ions or cations in in our case metal ions are going to be drawn towards the cathode cations to the cathode and then they will gain those electrons and undergo reduction so the cathode is where we actually get the metals being produced if we have reduction occurring obviously we need oxidation occurring as well because to get a I guess a a closed circuit we don't just need electrons flowing from the power supply to one electrode we need that electron flow to also come back in a full loop and for it to be a closed circuit so what we can then get on this other electrode are negatively charged ions or anions flowing to this electrode called the anode so again anions to the anode and they're going to be stripped of their electrons in other words they're going to undergo oxidation and that oxidation process which removes those electrons will then help complete that circuit we will associate a positive charge to the anode because this is where we are getting that removal of electrons back to close our circuit if we just think of in the simplest case an ionic compound made up of positive metal ions and negative nonmetal ions then we've got our positively charged metal ions undergoing reduction at the cathode but our negatively charged nonmetal ions then undergoing oxidation at the anode and so what that will then do is separate these metals from their combined form and help produce those metals in an elemental form as well as the nonmetals as the last thing we're just going to try and summarize this using an acronym and I used a similar one for galvanic cells but what you can see is that there is actually a difference in the charge of our different electrodes so what are these actually stand for so we have C n R standing for the cathode which is negatively charged but we know that the cathode is always going to be the site of reduction so that does not change the AP o would stand for the anode which is positively charged given that we're removing electrons at that point and it's always the site of oxidation taking place so my suggestion to use that you if you perhaps have some difficulty remembering this that you jot it down perhaps on some scribble paper in a test or an exam to help remind you of some of these different features so that if you are asked questions about you know identifying charge or identifying your anode or cathode or being able to specify what reaction is happening then this can be your goto just to help you out and the last thing that I just included is what's happening to the ions in that electrolyte so being able to associate the anions migrating to the anode where we get oxidation and then cations to the cathode where we get reduction happening when I did use a similar thing with galvanic cells it was actually about the ions in the salt bridge and how they migrated to help complete the circuit and to kind of prevent that buildup in charge okay so that pretty much concludes this first part of our work on metals and then obviously you guys will have a watch of the next one