[Music] Prem matriculant welcome to this is L extra live your favorite show your best learing show ever right here on 319 I am Abram and I'm not alone I'm with Tracy how are you Tracy fine and you happy uh woman's mind and I hope you enjoyed your women's day I was working but thank you all right it's all right I enjoyed it you know just well this is your month enjoy it thank you all right and what are we doing today today we're doing energy and chemical change it's actually a really nice section lots of little bits and pieces but it's actually it's a lot of fun I quite like the section it's sort of a introduction to stuff for next year all right if you like it so am I so let's learn more and learn extra my sisters if you're joining us now you're not late you just on time go over Facebook and like our page if you have EV but if you have make sure that you go to facebook.com/ extra like our page and let's get talking over the page if you have any questions and also if you need to help other mindsets that's what we are having Facebook for team mindset all the way let's help one another second thing that you need to know is that you can follow us on Twitter at Len extra and lastly download your notes all for free on Len extra. life so let's get to it learn more learn extra with Tracy a thanks okay well guys like I said earlier we're doing energy and chemical change this is the start of chemical system um chemical change for you for this year and we're going to cover quite a few things today and it's going to look like a not but it's not actually so what we're going to do is we're going to talk about the energy change in chemical reactions okay because that's quite important we're going to Define now exothermic and endothermic reactions I know you know what they are cuz you've dealt with them along the way but we're going to Define them now we're going to define a concept called Bond energy which hopefully you've actually come across before now right at the beginning of the year when you did bonding and you did molecules and you did shapes and you did Bond length and all of that sort of stuff we're going to Define an important concept called activation energy and the activated complex and then we're going to discuss potential energy diagrams it sounds like a lot but they actually all just work together which is really nice so we're going to jump right in there and we're going to talk about what is an X exothermic reaction now I know you know this because you've done this since grade eight already hopefully you were using the term exothermic reaction and remember that an exothermic reaction oh no that's not going to help me let me I don't know what happened here there we go it's yellow now really exothermic I was told the pen Works Pen's not working okay there we go let's try this again let's not do that let's use one of those okay there we go and EXO sorry that's my fault I actually can't remember how to use the board it's been so long anyway exothermic reaction is a reaction where the system becomes hotter so um you burn magnesium in oxygen gives off a flame gets hot we're all okay with that heat is given to the surroundings nice and easy now a good example of that is when we burn fuel okay this is the example here in that I've got is methane okay methane plus oxygen which gives me carbon dioxide water and energy now what's important here grade um 11s is that I've put the energy as a product okay it's not a chemical okay I'm not saying that energy has become a substance I'm saying that it is something that's given off we usually experience this in in the form of heat okay now an endothermic reaction is a reaction in which the system becomes colder these are a little more unusual you don't do a lot of those at school level but you can still deal with them and now it says that heat is taken in from the surroundings okay so take SE in a good example and the one I've got on the board here is with photosynthesis for so for the life science students you all have seen this before carbon dioxide plus water now what what we do here is we add energy okay as one of the reactants so instead of saying we give off energy now I'm saying I need to take in energy and I need to put it into the system okay I just saw a little bit of a typo so when you look at the no just take that art I don't know what I was doing okay another good example of an endothermic reaction is those disposable aspects you know if you're an athlete or you're doing something and you hurt yourself and you know you got to put ice if you twist your ankle which I'm quite good at just falling off stairs you twist your ankle or your wrist or whatever and you know you got to put ice on it and you can get those disposable ice packs now what those ice packs are is you break the inside there's a packet inside the the ice pack and then it goes cold cold cold cold that's an endothermic reaction okay because now you're forcing chemicals to interact with each other and they get cold okay you also know with those ice packs you can't keep them cold forever because eventually the reaction stops Okay so exotherm reactions reactions that give off heat endothermic reactions reactions that take in heat okay but this whole talk about energy we now need to give it a nice fancy name because we're doing science okay and that fancy name is eny okay eny which is given the symbol H I actually don't know why it's called given the symbol H I know it's confusing but just deal with it okay now enthalpy is defined as the total amount of chemical potential energy in a system chemical potential energy is the energy that a system has because there chemicals involved okay we can make use of that chemical potential energy by causing a chemical reaction which then results in heat we can use it to cause a chemical reaction results in electrical energy there's lots of things we can do with that chemical potential energy okay okay enthalpy as it stands isn't that useful but change in enthalpy is Delta H now when I talk about changeing enthalpy grade 11s what we referring to here is we're going How does the energy of the system change so when I look at how much energy I had when I started and how much energy I have when I'm finished what's the difference okay and do we then EXP experience that difference as heat does it get hotter does it get colder what exactly is going on okay and now this is important and whoops before I forget enthropy is an energy um it's measuring energy so we measure it generally in kog per per mole kles thousands of jewels of energy at a time per mole you know what a mole is you've done it lights up to this point you probably just finished do geometry so per mole of substance okay and we can do it per mole of reactant per mole of product however that works so it has a unit it's not a ratio it's a unit in an exothermic reaction okay Delta H is negative now this doesn't always sound like such a hot idea CU now you're going all right hang away you just said to me that an exothermic reaction is a reaction where I give off heat cool then we said eny is the amount of chemical potential energy we have we're okay with that but now I'm saying to you that if enal the changing enthalpy is negative then it's exothermic how how does a negative give of heat just hold that question for me grade 11s I promise I'm going to get back to it okay CU I know that's what you're thinking an endothermic reaction Delta H is now positive okay and now we got to think we go okay enthalpy is the energy of the system an exothermic reaction gives off heat to the system an endothermic reaction takes in when the Delta H is negative what what that means is the system is losing energy negative it's losing energy to the system the the reaction is losing energy to its surroundings endothermic Delta is positive because it's taking in extra energy from the surroundings okay that's great but how do we know we get in there okay so keep all of that in the back of your mind we're going to need it now now we need to talk about Bond en you did bond energy earlier this year okay when you looked at Bond length you looked at intermolecular forces and all sorts of things and one of the things you would have had to do is bond energy now bond energy is defined as the energy which um which is absorbed when bonds are broken or released when new bonds are formed now listen carefully when I break the bonds in a molecule I have to give it energy we want to break something that's already existing okay when new bonds are formed okay so now go from okay I'm breaking old bonds old bonds need to give in energy but why do atoms bond together atoms bond together because they want to get to a lower energy State how do they get to a lower energy state by giving off the energy okay so absorb energy when we break bonds give off energy when we make bonds okay going to keep this in the back of our minds that helps us work out changing enthalpy and we got a little equation here which will not be on the information sheet changing energy which is Delta H my enthalpy is equal to this is Sigma that means total the total energy absorbed when I'm breaking all the bonds minus the total energy released okay but where do we get those energies from well grade 11 you do not need to learn Bond energies now this is quite a comprehensive table that I have okay over here whoops if I don't just what did I do okay I don't know what I've done again no let's it's time for me to well Tracy while trying to figure no it's it's it's just it's just a w coming back it's a coming back I've got it I got it sorry guys you know what that's what makes watching the show fun yeah you know a live show AB absolutely anyway and it's just my fingers so guys there's a whole table here of bond energies which is kilog peral you do not need to learn these values please understand that in a test or an exam if you need to to use these values they have to be given to you probably what will happen is you'll be given quite a comprehensive table like this but you'll only need to use some of it okay there's no ways you'll ever have to use all of them and they're not going to just give you the ones you need cuz that would just negate you having to figure it out but this is kilog per MKS that's what we doing so what this is saying to me is that if I break a hyrogen H2 Bond okay I need 432 K per mole of hydrogen to put into the system to break the hydrogen away from each other but the converse of that is that if I'm now going to make hydrogen H2 I'm going to release 432 K of of energy per mole made okay that's what these what this table means now you should have seen something like this before because you would have spoken about things like Bond length bond order um for how bond energy changes okay but let's quickly look at a problem which will then help us decide on okay how do I use this in calculating if it's exothermic endothermic which is what this question says says calculate Delta H for the phone reaction is the reaction exothermic or endothermic okay so what we're going to do is we need to go find I need to calculate how much energy is taken in so over here okay over here that's my energy that's absorbed okay and yes I can write as well over here that's energy released okay so I need to work out total amount of energy absorbed total amount of energy released and I'm going to minus them from each other okay now do you know what I think Aram yes I'm going to get about halfway through this and then we're going to need to take a break MH so what I'm going to do guys is we're going to take a break but while we at in the break this is what I want you to do I want you to decide for me what bonds and how many need to be broken and what bonds and how many are going to be made because that's a very important decision before we can actually move on so I think with that with that I think they can take a break all right M SS help Tracy and then we'll see after the break how how did you help her whether you're right or not and let's continue on that note don't go [Music] anywhere welcome back m c is now as much as you need to help Tracy we also need your help as mindset we're looking to hire someone if you know of anyone who could be interested in doing some grade 10 to grade 12 caps aligned content development review and video presentation make sure that you go over mindset. Doland jobs because we're looking for that someone the closing date is the 26th of August so Tracy let's continue oh great guys seriously if you have a good science teacher please get them to do this it's such a wonderful opportunity okay so we're back and I'm hoping you managed to do what I asked you to do so let's just quickly get rid of my scribbles and we're going to talk about what is actually happening now the point here grade 11 is we need 12 to decide how much of everything we have okay so we're going to start with the energy let me have a pen that works energy absorbed okay so what we need to discuss is how many bonds need to be broken so let's look at this carefully what we have over here is we have a hydrogen fluoride Bond so it's HF and there's two of them the number in front is very very important here GRE lemons so we have two HF bonds and now we go well we have a cl2 we know that CL bonds with cl with single bonds so we only have one chlorine chlorine bond okay things like knowing that chlorine bonds to itself with single bonds is very important grade 11s it's those basic things that even though we're not testing you speci specifically about bonding at this point we still expect you to know it okay so you got to understand that everything is put together so let's go back to our table and see what we have there in terms of bond energy and that sort of thing and hydrogen fluoride HF is 569 so I'm going to be using this one and cl and cl is 2 43 okay I don't know these off my head just so you know I need to look them up so let's go back here okay yes there we go all right and we back at the HF and we said that was 569 and the chlorine was 243 which gives us 382 k per mole okay so we're okay with that 1,382 not a problem that means that I need to put in 1,382 K of energy per every mole of reactant in order to break everything up into its atoms okay then the reaction proceeds and now we need to look at energy released because we're making new bonds so we go back up and we say fine there we go two HCL bonds one Florine Bond okay so the B There we go all right two HCL bonds okay single bonds we know that plus one Florine Bond okay we go back to our table because this helps us decide what we've got and we said well we've got two HC bonds so it's 431 one Florine bond which is 159 so we're going to go back and obviously this is a little bit easier in an exam because you all have everything together you know and you don't have to swap three pages so now we get 2 * 4 31 + 159 and we get 1,21 K per mole so what is this information telling me gr 11s in order to break all the bones I needed 1,380 K of energy to go in when the new bonds are made I only give off $1,000 3021 K so actually I'm taking in more than I'm giving off that makes this endothermic okay but now we need to prove it because they wanted us to actually prove it so my changing energy which is what they asked for is going to be my total energy absorbed okay zorbed with a B minus my total energy release that little z e thingy funny symbol over there that's Sigma okay you know that from math okay so that means I'm going to go [Music] 1,382 - 1,21 and I get 36 60 K per mole now earlier today I said to you that if Delta H is greater than Z then it is an endothermic reaction this is very endothermic okay so this reaction because Delta H is greater than not it's an N let me take that off Delta H greater than not it's an endo thermic reaction okay it's endothermic it takes in energy from the system around it from the surroundings okay if if this was reversed and we went the other way around then it would be exothermic because we would have ended up with a negative answer okay so moving on now we get to some really really really important concepts for a chemical reaction to take place we at school level often only really discuss spontaneous reactions so reactions that maybe I need to add a little bit of heat to get it going but we don't need to keep adding heat or if we do heat it it's just to make it go a bit faster but generally we don't do a lot of nonspontaneous reactions so the whole concept of activation energy sometimes gets a little difficult to to get in our heads but what activation energy is is simply the minimum amount of energy I have to put in into the system in order for the chemical reaction to happen so we can put a whole bunch of chemicals together but just because they're there doesn't mean anything's going to happen we need to make sure that they have sufficient energy okay that sometimes that means we have to heat it up sometimes things happen on their own and you don't need to add anything to it there's lots of reactions where we don't have to add heat but that's just cuz they have a very small activation energy okay so activation energy when we look at this by reaction to happen between two substances just what I've said to you the minimum amount of energy there is a minimum amount of energy for the reaction to take place that minimum amount of energy is called the activation energy okay it's the absolute absolute minimum if the if the particles do not have that amount of energy they will not react no matter what you do okay you got you can stand on your face and go Blue it won't help okay they must have that minimum amount of energy you guys okay with that so but now what actually happens is this is like pushing a big rock up a hill okay takes energy to get up to the top of the hill but you're not at the top of the hill and now you going now it's like is the rock going to fall forward or is the rock going to go back down okay and at that point when The Rock gets to the top it's a place called The activated complex all the bonds get broken in the molecules in the reactant so all the bonds get broken and now they all come together in a big smush that's a nice scientific word okay so they all come together and now they're at a little bit of a halfway stage but at this this point we get an activator complex at the the activator complex is an unstable temporary complex you cannot take it out of the system I can't go all this activat complex and put it aside it doesn't exist outside of the chemical reaction when the activated complex gets made the system now has a has a choice to make either the activat complex is going to keep going forward and it's going to make the reactant so give off energy or it's going to go back down and make the re the so make the products and give off energy or it's going to go backwards and make the reactants again okay unstable it's temporary okay now so what we have over here is when the minimum energy has been absorbed we form the activated complex very important guys it is a temporary high energy unstable State it's almost like a halfway stage okay so it's a little like and I'm I'm probably going to show my age here like in The Matrix in the second movie I think it was when you got stuck in the train station you remember that have you seen it yeah okay so you get stuck in the train station that was like the activator complex because he could either go backward which he didn't really want to go but he really needed to go forwards but he couldn't stay there it wasn't like he could take the train station with him okay so that was like the activator it's that temporary State please don't write that in your exams okay your teachers will not understand it's just an analogy okay so it's a temporary high energy State all right now that gets us to our energy potential graphs these are are so useful and really really help us what I have here is the graph for an exothermic reaction okay now it's the reaction between hydrogen and oxygen to give us water hopefully some some of you may be seen this I particularly like doing this in my classroom can't do in the studio I'll probably break something but you fill a balloon with hydrogen put it on a string like the string string Burns blows up the balloon it's such a fun experience put a little bit of oxygen in the balloon at the same time big noise it's great okay very very very exothermic okay it's why we use hydrogen as a fuel now what this graph tells me first of all my y AIS is potential energy kog per mole it's related to enthalpy okay we start with the reactants and the reactants have energy because they exist okay the reactants have energy just because they exist otherwise none of us would exist okay they just have energy CU they're there those reactants now need to absorbing energy which is what we've just calculated with the last question they absorb in energy in order to break so we need to break up the hydrogen and the oxygen and the way we do that is we absorb energy so now the energy in the system gets bigger until we reach the peak this difference in energy over here is the activation energy that's the minimum if I add in more than that the reaction will go faster if I don't add any enough the reaction won't happen so that's the minimum at this point we get to activate a complex this doesn't have a formula grade 11s you can't tell me it's H2O2 because that's hydrogen peroxide you can't you can't do you can't say it's ho cuz that's it's there is no formula to this okay it's simply all those atoms bonded together while while near each other and this gives this complex at this point n new bonds need to be formed so we've taken in energy to break bonds Now new bonds need to be formed when bonds are formed we release energy so the goes from a place of lots of energy loses this energy and goes to a place of less energy okay we've now formed the product by forming the product new bonds performed we gave away energy the difference between here and here is Delta H that's my change in enthalpy okay the difference in energy between my reactants and my products is my enthalpy my reactant is a big number products is a small number and I'm going to go um oh we go products m i take the product energy minus the reactants energy and I'm going to get negative answer okay so here Delta H comes from is going to be equal to the energy of the products minus the energy of the reactants and I'm going to get a negative answer okay this the label for the x-axis grade 11s this has a there's lots of ways to label it except for one course of the reaction is acceptable reaction coordinate is acceptable um progress reaction progress is acceptable time is not okay you cannot put time on this axis ever I know some textbooks do you may not do that okay so in exothermic reac re action products have less energy than the reactants and I think Aram it's time for a break and then we'll do endothermic well it is you know talking about time you're reminding me of a quote by aav m yes he says um time is for free but it is totally Prim uh uh Priceless because everyone can can use it but no one owns it so time is not ours I need to know where he gets these from cuz you were doing all the NS and Mandela ques last time too I remember this I'll give you my secret after the break stay tuned m s don't move also we'll see you after the [Music] break welcome back pratul now the curio is up and available just waiting for you go to curio do. Za and fill in that assessment do not skip any question because we'd like to help you to see whether you understand or where you still need some help so it is curio your code is ps11 you can also log in to curio via your mixit at dat a contact curio thank you excellent well that just came out on the way okay so before the break we said we take Del we take enthalpy change in enthalpy is energy of the products minus energy of the reactants and with an exothermic reaction the products have more have less energy when we're finished so if an exothermic reaction gives off heat and an endothermic reaction takes in heat so it's the opposite if we look at the graphs and we go well an exothermic graph means that the products have less energy than the reactants then an endothermic graph must mean the opposite okay so if we look at the endothermic graph okay the same thing now it's a different reaction okay please note this is not carbon dioxide and carbon monoxide it's a different reaction okay I can't use water hydrogen and oxygen again because that is an exothermic reaction I can't change that to an endothermic reaction but the same concepts are happening so we have our potential energy on the y- AIS we have course of reaction which I said to you earlier can also be reaction coordinate or Pro or um reaction progress but cannot be time now the reason why why it can't be time now I've been explaining it one way and I got told a much better way today so it's actually really good is if your x-axis is your one yeah your x-axis is time that would be zero time time at zero time we have particles inside that system which has a certain amount of energy if this is a time graph then what this graph is telling me is that at every moment in time every particle has exactly the same amount of energy which is not the which is not what happens okay when we look at the temperature of a system we're looking at the average kinetic energy that is that the particles have so we can't actually do this by time because then the graph would be all over the place so we can't use time because not all the particles are doing exactly the same thing at exactly the same time okay cuz it's random remember that in a chemical reaction grade 11s you're actually looking at a reaction where you have millions of atoms and molecules and compounds bashing into each other at the same time you cannot predict essentially what each of them are going to be doing at a specific point in time okay so if we now look at this m go let's go back to what the what it's telling me my reactants have a certain amount of energy because they exist they have to take in energy till they get to the activated complex the energy that they take in is the activation energy so activation energy is still the difference in energy between where the reactants are and where the activated comp Lex is okay so if I know those values I can work it out then we the activator complex is happy to move forward moves on to the forward reaction so now we get our products and the products give off energy as they get to in but they give off they end up with more energy so if you look at this they end up and that's just not a straight line but just pretend this is my product's energy over here and this is my reactants energy and my reactants now have more energy so I have less energy my products have more energy than the reactant did that means the products took in energy from this from the outside which is where the activation energy comes from but when the new Bonds were formed this is like the calculation we did less energy was given off than they took in that also means that Delta H which is the difference between the energies is now uh positive Delta H is positive okay this is all nice but you know what honestly as humans we don't like things to go slowly we like things to go fast so we can use a very important thing called a catalyst now a catalyst can increase the rate of a reaction without actually taking part in the reaction sometimes changes face but it doesn't actually take part what a catalyst actually does is it lowers the activation energy so if we look at a energy graph okay this is for a exothermic reaction now whether it's an exothermic reaction or an endothermic reaction it makes absolutely no difference a catalyst does exactly the same thing here's my original activator complex by adding in a catalyst my activ to complex is now over here it's lower okay a catalyst it's fairly complicated chemistry so we're not going to worry too much about it but a catalyst helps the reactants get to that activated complex part where it needs to get once it gets there then we can make the products okay so Catalyst makes the activation energy smaller but it does not change Delta H okay a catalyst does not change the change in enthalpy that is constant because the reactants have a certain amount of reaction of energy the products will have the same amount of energy regardless of how it got from reactant to product that that doesn't matter to the enthalpy okay how we got there whether we have a big hill or a little Hill doesn't make a difference as long as we get there that's all that matters okay so that brings us to the fun part questions okay so what do we have here during the process of cellular respiration glucose is broken down to form carbon dioxide and water according to the following reaction so we have C12 C6 h12 um plus 602 goes to carbon dioxide and water the reaction is catalized by by enzymes what they're saying to you is this is a reaction we we create in carbon dioxide and water okay this is what happens when we breathe by the way and break down I think I think cellular respirations when we change um sugars into carbon dioxide and water okay sounds like we're doing life science a little but life science and science often cross over catalyzed means that we can speed up the reaction by using enzymes we don't need to know what those enzymes are we don't need to know they names we don't need to know their functions or what they look like or it's not biology okay it's just catalyzed the change in potential energy during this reaction in the human body is illustrated by the graph so we go okay let's see what they've given us note that this graph instead of saying course of reaction is called progress of reaction reaction progress same thing okay my reactants this is my activation energy so they've labeled it nicely for me there's Delta H there's my product and looking at this I realized that my products have less energy than my reactants so straight away I'm just going to make a note for myself that this is an exothermic reaction okay we're okay with that first thing they ask use the graph to answer the following questions okay that makes sense first part is the breakdown of glucose an endothermic or exothermic reaction we've just answered that because I said to you looking at it that it's exothermic okay you see I've written it over here it's exothermic okay why did because now they ask you why the energy of the products is less than the energy of the reactants okay so it's an exothermic reaction why energy of the products less than the energy of the reactants fairly straightforward now they say explain how the enzymes influence the rates of reaction and now you're going we haven't discussed rates of reaction tracing no we haven't but let's just talk about the enzyme is a catalyst so what the enzyme is going to do if we look at this reaction is it's going to make my activator complex happen at a lower height okay it makes the activation energy smaller as soon as we make the activation energy smaller we make it easier for the reaction to happen if it's easier for the reaction to happen the reaction will happen faster that's the point of using a catalyst you do get catalysts that decrease they make it go slower okay but we're not worried about that at this point for school level the point of putting the Catalyst into a reaction is to increase the rate to make it go faster now in the human body this is all done naturally with the enzymes but in Industry why do we need a chemical reaction SC fostter we want more product if we get more product at a faster rate we make more money okay because that's pretty much why we do anything in industry is to make money it's to help the economy so that's quite important for us so when it asks you so the question said okay let's get back there expl explain how the enzymes influence the weight rate they don't just say how does it explain so we we' say the enzymes increase the rates of the reaction by decreasing the activation energy okay how they increase the ratees of reaction they decrease the activation energy okay we got that all right we have time for another question okay okay I like this one in the following energy profile diagram guys I've used a lot of words I need different names for these things and you need to get used to it's the same thing it's the energy potential diagram okay the xaxis represents the extent of the reaction or the reaction progress the Y A AIS represents the energy of the reactants or the product so we go well it's okay if we look at it looks a little different cuz this was obviously drawn on a computer and we go well they've given it values which is always interesting -50 100 600 don't worry about the fact that you got - 150 above the line it's it's in FSE exam paper so don't stress about that um and we got okay high energy low energy it is a exothermic reaction okay exothermic reaction and we go well that's obviously where the reactants are where is C and D is my um products I don't know what AM is and it does matter it's a general reaction that could be anything okay and they tell me over here that it's reversible reaction at this point that's not that important grade nine um grade 11s but what it does mean is it actually gives us the ability to read the graph backwards if we wanted to okay so if we going from a plus B to C plus d it's exothermic okay cu the reactants end up the products end up with less energy then the reactants if I go the other way around product two reactants it's endothermic they always work together so first question label provide names for the labels one to 4 okay and I'm hoping some of you are screaming at your TV right now going oh we can do that so number one is over here and number one is the distance between the energy of my reactants to the top part by my activator complex which means number one is my activation energy okay activation energy all right we all okay with that number two number two is the difference in energy between my reactants and my products which means it's Delta H it's my enthalpy you all still with me number o number three this one's interesting CU I actually haven't spoken about this number one is the activation energy when I go a plus b go to C plus d so this is actually the activation Rea energy for the forward reaction when we read the reaction from left to right if I now go from C plus d all the way up the H to a plus b I need to add in a lot more energy that's what number three is number three is the reverse reaction activation energy so if I want to reverse it I need to put in more energy which hopefully makes sense it's like a rechargeable battery a rechargeable battery when it when we're using it as a battery and it's applying current it's spontaneous reaction doesn't need a lot of help off it goes in order for it to reverse for it to go back to be able to SP C you have to add energy to it and it takes a lot of energy so we have to plug it in and recharge it so this is what we mean by reversible it can go in two directions if the One Direction is exothermic the other direction is endothermic but what's very important to note here number four here is my activated complex now the activated complex is the same whether I'm going forward or backwards doesn't make a difference forward backwards activat complex exactly the same okay no issues there all right now they so so we' got the same diagram calculate the activ calculate the activating energy for the for reaction shown on the graph so now we've got to go okay the activation energy is the difference from here to here so in other words it's the difference between the 600 and the 100 so let's write it in over here okay so my activation energy which we can call EA okay is going to be now I could write en let's not get complicated okay from the graph we saw that it's 600 - 100 so it's 500 now let's just check what unit it's in given to me over here kilog per mole okay make sure you use use the same units sometimes they don't have the per mole it depends on the question so use the right units calculate the overall enthalpy for this reaction enthalpy means Delta H so as an equation we're going to go I'm going to have to take Delta H and I'm going to take the energy we need to actually write to is an H sorry we're going to take the energy of the products minus the energy of the reactants now I know you're busy going Tracy why is it h and not e because we looking at enthalpy okay so we so even though we're talking about energy enthalpy is just a nice special word and in chemistry we use H so now we look and we got okay the products minus 150 the reactants 100 so that means I'm going to have to go- 150 - 100 and we get - 250 kilog no that L is terrible kog with a small k k per mole okay very exothermic negative it's exothermic okay so AR yes I'm pretty much done but if I before I do a summary do you think there any are there any question here's a quick one please explain to me what is meant by activated complex in simple words okay in simple words yes okay the activated complex basically is if we look let me get to a blank page okay so let's look at the water one okay so we had hydrogen plus oxygen now hydrogen if we do it in dot molecules I'm sure you remember doing this when in grade nine so that's pretty much what they look like the activat complex happens when as these two come along okay they now form a big little compound that maybe looks like that okay it's just they all put together but this is stable it can't stay like that it's got so much energy it's like when you drink energy drinks and bounce off the walls and drive your teachers mad okay um get so much energy it's got to give it away so either the activator complex is going to make the new bonds or it's got to stay with the old ones but it can't stay where it is so it's temporary and it's very unstable it's it's a halfway station it's like the halfway stage before it decides what it wants to be y i I hope it answers that way can you take a quick one also another one um how okay when when when will you do uh friction oh friction we did that earlier this year so in terms of FR and sweee go look back in thee we did it right at the beginning of the year when we did Newton's Laws so it's all it's on the it's on the website the notes are there the videos are there I wanted you to tell them actually okay the video is there on YouTube also it's there on YouTube guys the the the the notes is still there and the videos there and we did do it we did the year and the notes and the notes yeah we pretty much yeah we've pretty much finished physics for the year wow unfortunately time flies especially when you're learning so fast and so much otherwise Manors thank you for tuning in and thank you for taking your time to learn with us mind C is grade 11 go to cir. and fill in the assessment your code is PS1 from us Tracy and ab we just want to say thank you very much peace [Music] [Applause]