hello and welcome to the chemistry Academy in this video we're going to go over fuels in relation to the National chemistry course so just to get started there's a few definitions that we need to know and for this subtopic so there's a good idea to get these on some flash cards write the word on one side and the definition on the other and then you can play a little division game with yourself and by having either side visible so you have the definition and you have to guess not guess but know the term and then you can also have you display the side where you have the term visible and then you have to recite the definition you can also get friends family to do it with you like a we quiz um so the main definitions you need to know are the definition of a fuel so that is a substance that burns in oxygen to release energy so these are things you really need to know word for word changing words slightly can sometimes mean that you don't end up getting the marks so quite often with the fuel definition people will say a fuel is a substance that can produce or create energy that's not the case you can't create energy energy just exists and it just changes from one form to another that's going to take us into the realm of physics so we'll just go as far as that so just try to remember a fuel is a substance that burns in oxygen to release energy okay then we've got hydrocarbon so a hyd hydrocarbon is just a substance that contains only hydrogen and carbon atoms so that's why it's called a hydrocarbon kind of just done a wge we taking hydrogen and carbon put them together so that's what hydrocarbon is an exothermic reaction is a reaction that will release heat energy so it will feel hot if you touch it and an endothermic reaction is the opposite that's a reaction that takes in or absorbs heat energy from the surroundings and therefore it will feel cold when you touch it so examples of these reactions in everyday life if you've got hand warmers they create an exothermic reaction within the Sashi so when you burst the we thing in the middle or crack it up that starts the reaction and then the heat energy gets released to the surroundings which then makes it feel warm for you to touch an endothermic reaction example would be the opposite of that where we get the ice packs that you crack and them to go cold so again when you crack them or burst we packet inside of them the EXO endothermic reaction will start and therefore it absorbs heat energy from the surroundings so it makes it feel Cold okay exothermic gets asked about more than endothermic but just make sure you do know both of them so that's the main definitions really so like I said get them on some flash cards and get learning them so if we then go on to how the fuels burn to release energy so when when a fuel Burns it does so in a combustion reaction so the reaction of anything burning in oxygen we got here is classed as a combustion reaction so if you see a substance reacting with oxygen it's quite likely that it's a combustion reaction isn't always a combustion reaction because there are other things involved reacting with oxygen and but it is a potential that it is a combustion reaction in order to identify if a reaction is actually a combustion reaction or not we then would go and double check what the products were okay so we're looking for oxygen as a reactant then there's also certain products that we'd be looking for so in the case of what we call complete combustion so this is the combustion that you normally would come across the complete combustion happens when you have a plentiful supply of oxygen so there's lots of oxygen around it's really easy for stuff to burn because everything is burning in the oxygen so the more oxygen you have the more likely the combustion reaction will be complete complete combustion is when the substance Burns in oxygen and the products are carbon dioxide and water okay so that's the key products of complete combustion however this is only if you burn like a hydrocarbon so something with carbon and hydrogen or like say an alcohol that's got carbon hydrogen and oxygen in it those are the products you tend to look for when you're looking to see if a reactions a combustion one you want to see carbon dioxide and water um and oxygen as the reactant so carbon dioxide water is the product oxygen is the reactant and that's for if it's complete combustion where you've got a lot of oxygen present like I said if you have some other um elements present you can sometimes produce other things we're going to go through some examples here of combustion reactions so where things are reacting with oxygen and work out what the missing products would be just so you can see how it kind of works so if we look at this first example um we've got two carbons or C C2 H6 so that's ethane and it's reacting with oxygen the three and a half moles here doesn't really matter just I meant to out and so basically what happens is every atom in the fuel the thing you're burning reacts with oxygen to produce something so the carbon will react with the oxygen and makes carbon dioxide that's the common carbon and oxygen compound that we know of and then the hydrogen also reacts with the oxygen and produces water which is another common compound containing hydrogen and oxygen that we know so that's the products when you burn a hydrocarbon something that just contains carbon and hydrogen me carbon dioxide and water okay we'll not bother balancing this CU um we can come back and do that at the end um if we then look at this next example here we've got a fuel with carbon hydrogen and sulfur in it again burning in oxygen so we take the carbon reactant with the oxygen that'll will produce CO2 if its complete combustion the hydrogen with the oxygen would make the water and then this time we've got sulfur to react with the oxygen so that makes a gas called sulfur dioxide now sulfur diox oide gas is very bad for acid Rin um so it's harmful for the environment because it causes acid rain so what happens is the sulfur dioxide dissolves in rain water and produces sulfurous acid um and therefore when the rain comes down it's acidic and it can kill a lot of plant life and damage aquatic systems and things so that's the gas you need to remember as the one that causes acid rain okay so really you shouldn't be burning fuels that contain sulfur because if you burn any fuels that contain sulfur we end up producing sulfur dioxide which is harmful and causes acid R okay so my usually we would not remove use as a fuel and you would remove the sulfur first if you good because of this problem here okay if we then look at this example here so I've kind of done this back to front that should technically really be a gas it's it's a hot environment and so this time we've produced water water is the only thing we've produced that means we can work out what the fuel must have contained so we know that oxygen comes from the air so we can't that's not necessarily going to been in the fuel so the only element that's left or is hydrogen hydrogen are the only atoms left we need to have in our reactants so the fuel must be hydrogen gas which would be H2 because it's datomic so any element in the product that's not oxygen must have been in your fuel okay um because atoms can't be created or destroyed they have to just turn again from one compound to another so if you had hydrogen atoms or carbon atoms in your product you must have had them somewhere in your reactants but the oxygen can come from the air so it's not necessarily always in the fuel okay so just bit we note here any element other than oxygen in the products must be in the fuel okay or the substance that's burned then we've got H this experiment here that you'll see sometimes just come to this side so this is where we've got um we're burning a fuel or substance and we're trying to identify what the products formed are helps identify what the fuel might be so the first uh collection that is usually where you've got a nice bath so cold water around um that container so when the gases of what are being the gases that are being produced when the fuel Burns they'll travel through the tubes here and then when they get to this cold Beaker because it's surrounded with a nice bath and sometimes you will get a colorless liquid forming and that's because gases have condensed and formed a liquid if you get a colorless liquid that means you have produced water okay so if you get a colorless liquid in that container then it means you produce water when you burn your fuel then the rest of the gases that haven't condensed they'll keep going along this tube until they get into this test tube of lime water at the end hopefully you remember that carbon dioxide turns lime water cloudy so if the lime water goes cloudy it means you made carbon dioxide if it doesn't it means you've not made carbon dioxide okay so what does this mean well if we've produced water and carbon dioxide so you got colorless liquid in here and your lime water turns cloudy you must have had a hydrocarbon at least that you've burned okay because you needed to have carbon hydrogen coming from somewhere to produce the water and the carbon dioxide if you find that you produce a colorless liquid but the lime water does not turn cloudy it means you've made water but you haven't made carbon dioxide so that means whatever you've burned must have contained hydrogen the hydrogen that's in the water but you haven't had any carbon in your fuel so it's most likely that you've burned hydrogen fuel or maybe something that contains hydrogen and other atoms but no carbon okay so that's how identifying what the products of combustion or can help you work out what elements must have been in the fuel cuz like I said any element other than the oxygen must have been in the fuel that you burned and if the element's not in the products then it can't have been in the fuel either okay that's not to say that the fuel can't contain oxygen of course we know alcohols are very good fuels and they contain oxygen um but we just can't say for sure when we're burning a fuel and identifying the products that there is definitely oxygen in the fuel because the oxygen could be coming from the air okay so that's generally complete combustion like I said we could have balanced these equations um but we'll save that for the balancing equations video um so what we're going to do now is talk about another type of combustion reaction it's not complete combustion but it's known as incomplete combustion so this is where we have a limited supply of oxygen as opposed to a plentiful one so for incomplete combustion this is like I said when you've got a limited supply of oxygen and this is where the substance will still still burn in the oxygen but because you've only got a limited supply of the oxygen you'll only produce carbon monoxide So Co rather than CO2 H carbon suit that's like solid black carbon everyone usually knows what suit is and and then also you will meet the water as well so if we take the Ethan that we had before and burn it in The Limited supply of oxygen this time then we will make the carbon monoxide carbon suit and water the problem with this is that carbon monoxide is extremely toxic to humans it will actually kill you because um you don't need to know this for chemistry but just for general interest and the reason it kills you is because it attaches to your red blood cells because it has a similar shape to oxygen so your red blood cells start carrying the carbon monoxide around your body instead of oxygen and essentially you kind of suffocate because your muscles and your body's not getting enough oxygen and so most houses now will have carbon monoxide detectors in them because um it's known as the silent killer the Silent Assassin because you could be sitting in your house if your boiler's broken and it's not getting a plentiful supply of oxygen in it the fuel in your boiler is not burning properly it could be producing carbon monoxide and it's going into your house and then eventually it could potentially kill you so there's a lot of carbon monoxide detectors in houses these days as a legal requirement for this and so just remember that that gas carbon monoxide is toxic poisonous to humans carbon suits just not good for the environment either it's also if you we in your house it's not good for your lungs because it's black solid suit you can be breathing in um so we want to avoid Inc complete combustion whenever we can okay so main things you need to know about that is being able to identify if a combustion reaction is incomplete and that would be looking for carbon monoxide as one of the products as well as potentially suit um and just knowing that that's what we be produced if you were burning something in a limited Supply and also KN that the carbon monoxide is classes being toxic so just to finish off we're going to go through a few different types of fuels you'll come across just give you some of the pros and cons to them because this can sometimes be asked about as well so we start off with the fossil fuels and mostly these are cons cons cons and so we've got coal oil and gas coal comes from the land we mine put it on land oil and gas come from out in the sea so that's where all the oil rigs go out and get oil and the gas um of course everyone knows that fossil fuels are harmful to the environment but you need to be a bit more specific than that if you're asked about it in your exam you need to specifically relate it to that they produce a lot of carbon dioxide which would contribute to global warming and or you can say that they produce a large number of greenhouse gases like carbon dioxide okay so you need to be as specific as that if you're asked about why a fuel is good or why it isn't you need to link it back to what's it producing and is that good or bad for the environment the other problem with them is that they're known as being finite so that word means that they will eventually run out close my bracket here and so that's another not great thing about them we're going to eventually run out of them however the good thing about them is they do have a lot of stored energy so they are very good fuels like they give us out a lot of energy so despite them not being good for the environment they're they have a lot of energy in them which is what you're wanting a fuel to do is to release energy so that's why we've used them for so long really um but really fals FS are not good then we move on to alcohols so alcohols are any alcohol you can use as a fuel and the good thing about all of the alcohols is that they have less chance of complete combustion taking place because the molecules themselves contain oxygen so this is a methanol here as you can see it's got an oxygen atom in it that means that you need to have less oxygen coming from the air in order to produce your carbon dioxide CO2 and your water so people say they burn more cleanly what that really means is that they're less likely to undergo incomplete combustion so there's less chance of suit and carbon monoxide being produced and is because like I said the molecules themselves have oxygen atoms in them so you need less oxygen atoms coming from the air the other one that's a positive but this only really applies to ethanol is the ethanol is renewable because we make ethanol from plant material and and then if we burn the plant material it turns into carbon dioxide and water and then plants take back in the carbon dioxide from the atmosphere eventually it creates a renewable cycle so the ethanol is renewable all the other alcohols technically aren't renewable though um the bad thing about them though is that they do require you then growing crops and that can take up land mass that could be used to grow food otherwise and because if you're growing the crops just to produce fuel you're not for like cars and things you're not growing it to produce food for humans so that's one of the downsides of it is the big land mass it does take up and then lastly we've got hydrogen so it's a renewable fuel because it burns to produce water and and then we've got obviously water cycle and we can take the water and split it back up into oxygen and hydrogen to make the hydrogen fuel again so the good thing about it as well as been renewable is that it's not harmful environment because like I said it only produces water when you burn it so there's no greenhouse gases there there's nothing that's harmful to the environment nothing that's toxic to humans the downsides to it though are that is quite expensive to make the hydrogen in the first place and also there's just quite a high risk of explosion that comes with it I don't know if you ever did the hydrogen B when you were in like first year of um science and I'll try and find a video of it and put it here basically if you have a balloon of hydrogen and stick a and Flame near it it just goes like massive explosion and so if you were to crash your car that could be potentially what would happen and if there was any ignition Source near your fuel tank so lots of work going into that for making it safer um as a potential fuel so that'll just be to do with how they design the cars and things how they get around that and so yeah the last thing we're quickly going to touch on is fractional distillation though it's not doesn't always come up and but it might so I'm just going to quickly run through it just so that you are aware of it finishing up with fractural distillation so when we take oil out of the sea it comes out as a big mixture known as crude oil and it basically contains lots of different lengths of hydrocarbon chains within it now the crude oil is actually no use when all of those hydrocarbons are mixed in together it's only useful when we separate out the different sized hydrocarbons into different sections and use them separately so this is what we call a fraction so a fraction is a group of hydrocarbons of similar length that can be used for a certain purpose now fractional distillation is just a form of distillation where you increase the temperature and allow things to separate based on their boiling point that's how distillation works we essentially heat up a mixture until certain things start to boil off because everything every different substance has a different boiling point so on an industrial scale fractional distillation you have the big massive Frac fractional distillation tank and it's cooler at the top than it is at the bottom at the bottom it's very hot at the top it's much cooler and you'll notice that all the way along there's different levels that have sort of different bits that have you can collect things off and each of the different levels with their own different tap if you like is known as a fra action so at the very top you get the molecules that have the lowest boiling points so they evaporate the easiest turn into a gas and and that's where you get the gases so for example like butane gas used when you go camping things like that so they all get collected off the top of the fractional distillation column then down the bottom you have um really thick gloopy substance because the hydrocarbons are really really long and and that is not actually used for taring RS um so it's a really thick grippy substance we can't use it as a fuel we can use it to TI roads and that's known as the residue we then have all the different fractions in the middle that are used for different things you can see here one that you'll sometimes get asked about is kerosene which is used as jet fuel so just remember that kerosene is the fraction that's used for jet fuel other than that you've got petrol and Diesel and you've heard about all these things in day-to-day life the only difference between them really is the length of the hydrocarbon chains like I said the smaller molecules have the lower boiling points so they get collected at the top and then the bigger molecules have the higher boiling points so they would end up down at the bottom you also will see here mentioning viscosity viscosity is just like how thick and gloy something is so the smaller molecules that are gas at the top have a very low viscosity whereas the thick gloopy residue that's used to Tire the roads is very viscous okay so you really just need to remember that the smaller molecules have the lower boiling points under less viscus and the bigger molecules collected down the bottom have the lower sorry higher boiling points and are more viscous so I hope that helps you with fuels if you find this video helpful please give it a like don't forget to subscribe and I'll see you again soon