Hi, guys. Welcome to my Edexcel GCSE 9-1 all-in-one chemistry video. Hope you find it super helpful. I'm not sure how long it's going to be, but I have gone through it and tried to make sure I've hit every single specification point. All my perfect answers flash up. And don't forget, if you want to buy my revision guide which I have written, containing my perfect answers, you can get that on the website ... which will flash up now. I hope you find this video super, super helpful. I hope your studies are going well. Don't forget to come follow me on Insta, Twitter, and Facebook because I add lots of extra exam tips, extra explanations, and just general cool science stuff, particularly on Insta. So I really would recommend giving that a go. And I do go through past papers there, too. So, yeah. I hope you find this video helpful. Let's get started. Group 1 elements now. So remember, that is the first column of the periodic table. It is the alkali metals. They all have the same chemical properties because they have one electron in their outer shell. Now, remember, as you descend that group, the elements become more reactive. They're all extremely reactive as it is, but as you descend the group, they get more reactive. The reason for this is because, as you descend the group, the atoms get larger, because if you actually look at their atomic number, it's higher for potassium compared with lithium, so the atoms are larger. This means the outer shell electron is further from the nucleus, which means that it's more shielded by the inner shells of electrons. This means it's easier to lose the electron. And remember, when we lose the electron, that's when it partakes in chemical reactions. So it's more likely to do that, so it is more reactive than elements higher up than it in the periodic table. I've already touched on the fact that Group 1 metals are extremely reactive. This means that they must be stored in oil because they'll react with the slightest bit of moisture. They're soft, and you can actually cut them with a knife. And they oxidize very easily, so they go from being shiny to oxidized very quickly on exposure to air. Other properties they have is they have low melting and boiling points, which makes them quite unusual for metals. And they also have a low density. And we can see this when they're placed in water, they actually float on the water. So again, these are really quite unusual properties for the Group 1 metals. Now, they're very reactive, as I've already said, and they can react with oxygen to form oxides - so potassium oxide, for example. They can react with cold water to form hydroxides - potassium hydroxide, for example, They can react with the halogens - remember, those other elements in Group 7 of the periodic table - to form something like potassium chloride. And they can partake in ionic bonding. Let's now look more closely at observations when they're added to water. So, this will be true for all Group 1 elements. First of all, they fizz, and what actually means is they're releasing hydrogen gas. They float. They move around. They form a small ball, which eventually dissolves. If you were to add universal indicator to that leftover solution, you would see that it would turn blue, and that makes sense because remember, blue indicates alkali, and they're called the alkali metals, so that makes perfect sense. In terms of more specific observations, remember that lithium doesn't produce a flame. However, sodium produces an orange flame when added to water, and potassium produces a lovely lilac flame. Learn the word equations for when they're added to cold water. So, I've already touched on this, but a Group 1 metal plus cold water will produce a metal hydroxide plus hydrogen, which makes sense due to the fizzing that you witness. So, taking lithium, for example, plus water forms lithium hydroxide and hydrogen. We don't add them to steam or to acid because that would be incredibly dangerous. They also burn in air, and they produce very characteristic flame colors. So lithium burns to form a red flame, a crimson flame. Potassium, again, produces a lilac flame. And sodium produces a yellow flame. In terms of making predictions about Group 1 metals below potassium - so things like francium. Now, you don't need to learn these observations off by heart, but do notice that these observations with water will be more violent because obviously for all the reasons we already described: the atoms are larger, more shells of electrons, the electron further from the nucleus. So just be prepared to talk about the fact that there'll be more violent but you'd still see the same set of observations: fizzing, for example, a flame, moving around, floating, melting, et cetera. Right, so, the halogens, we're looking at Group 7. So these are the elements including fluorine, chlorine, bromine, and iodine. Now, don't forget their states at room temperature: fluorine and chlorine are gases at room temperature; fluorine is a yellow gas; chlorine is a green gas. Then you have bromine, which is a red brown liquid. And finally, iodine is a grey solid. Don't forget: iodine undergoes a process called sublimation, which is when it turns directly from a solid to a gas. And in the case of iodine, it goes from a grey solid to a purple vapour. Now, the halogens react with hydrogen to form hydrogen halides. For example, hydrogen plus bromine forms hydrogen bromide. These are very acidic and poisonous ... and they're also very soluble in water. So something like HCl gas will turn readily into hydrochloric acid, so that's HCl aqueous on addition with water. You need to know about halogen displacement reactions, because more reactive halogens will displace less reactive halogens from their compounds. Let's quickly look at the reactivity of the halogens. So, remember, at the top of the group, that's where they're most reactive; towards the bottom, they're at their least reactive. And we can look at the reason for this. So, iodine is much less reactive than fluorine because iodine is much larger, so it has far more shells of electrons. This means that the outer shell electrons are farther away from the nucleus. They're more shielded, and because of that it's harder to gain that extra electron in order to become full. Hence, they are less reactive, and this helps to explain why iodine is solid at room temperature. So, if we look at a halogen displacement table, we tend to only look at the elements chlorine, bromine, and iodine. You'll find that chlorine displaces both iodine and bromine from their compound. You clearly don't react chlorine with itself - so potassium chloride - because there'll be no reaction. If you try and displace a potassium chloride, for example, using iodine, that won't happen because iodine is less reactive. So just learn the rules for this and the summary equations. (no audio) In terms of their general properties, remember, they have low boiling points and low melting points, and they are poor conductors of heat and electricity. Let's look at some various uses of halide salts. So sodium chloride, you might recognize already; that is actually table salt, so that's what you put on your chips and to make your food more flavourful. So NaCl is table salt. Sodium fluoride ... you find this in toothpaste, and you might see it on the side of a packet: 'Contains fluoride' ... because it helps to harden teeth. And make sure you don't swallow it because, although it's good for your teeth, you don't want it in your digestive system. Sodium bromide ... NaBr. That's found as a disinfectant in swimming pools. It kills pathogens and microorganisms. And then lastly, sodium iodide ... NaI, is an additive added to table salt. So, as well as reacting with metals, halogens can also react with hydrogen, this time to form hydrogen halides. Taking hydrogen plus chlorine gas - remember, both of these elements are diatomic - you're going to form hydrogen chloride gas. That's now balanced. And if you were to dissolve that into water, it would become ... hydrochloric acid. But as a gas, it's known as hydrogen chloride. If it's added to water, it becomes hydrochloric acid. And remember, from the covalent bonding topic ... hydrogen chloride looks like this. We have a covalent bonding diagram. As a side point, if they ask you for the test for chlorine gas, you just need to say that it bleaches ... damp litmus paper, so it will turn it white. Let's now look at how we can determine the reactivity of halogens. And the way we do that is by heating it with iron wool. So, we need to look at our various observations. So we're going to list our halogens and look at their effect on the iron wool. So with fluorine gas, you see flames with iron wool. With chlorine, we see that it glows brightly. With bromine, it glows red, but only dully. And with iodine, we see a change in color, but no glowing and no flames. So having a look at these observations, hopefully you can see the fact that fluorine bursts into flames. The fluorine is the most reactive. And we see the least change with iodine, so it is the least reactive. (no audio) Let's look at Group 0 now. What is their name, otherwise known as? It is the noble gases. And why are they so unreactive? And that's because they have full outer shells, which means they don't really want to get involved in bonding. Let's look at the noble gas uses, then. So, starting with krypton. Now, interestingly, krypton produces a bright white light when electricity is passed through it. So it's used in lighting systems and actually also photography. Argon, now - because it's extremely unreactive, it got used as the atmosphere surrounding light bulbs. And it had to be the old-fashioned filament light bulbs here. It's also added to wine barrels to prevent the oxidation of the wine ... because oxidation of wine causes it to lose its flavour. Helium, you're probably familiar with that. You find it inside balloons and airships ... so, party balloons, the ones that float, contain helium ... and the reason why is because helium is less dense than air. Don't say that it's light. And hydrogen used to be used because it's also got extremely low density, but the difference is that hydrogen was extremely flammable, which meant that it was dangerous because it was liable to explode, whereas helium is non-flammable. And lastly, neon. You find this in illuminated signs. So, places like Tokyo, Hong Kong, Soeul ... they contain neon signs everywhere. They're super bright. And the reason why it can be used for that is because it produces a red-orange light when electricity is passed through it. Now we're moving on to rates of reaction. So, looking at the effect of temperature, surface area, and concentration on rates of reaction - so what effect does increase in temperature have on the rate of reaction? Well, clearly it's going to increase it. The reason why is because particles have greater kinetic energy, so they collide more frequently. The collisions are harder, and therefore, a greater proportion of these collisions result in the required energy to overcome the activation energy. Looking at concentration now - so if you increase the concentration of particles, that means that there are more particles in the same volume. Clearly, collisions will occur more frequently, and therefore, the rate of reaction will increase. Surface area now - if you increase the surface area, for example, by powdering marble chips - powdered marble chips have a larger surface area than giant lumps, and so by increasing the surface area you're ensuring that you have an increased frequency of collisions, and therefore, the rate of reaction will increase. And do make sure you can argue this from if you decrease the surface area, decrease the concentration, and decrease the temperature. You just need to say the exact opposite. Remember, there are several ways in which you can measure the rates of reaction. So, rates of reaction are given by, for example, a change in volume over time ... a change in concentration over time. Now, if we use the marble chip example, remember that marble chips when reacted with hydrochloric acid, they will produce carbon dioxide. So, you can measure how quickly that carbon dioxide is produced either using a top pan balance - now, remember, that needs a high resolution because carbon dioxide doesn't weigh very much, so you need at least, like, 0.00 on your weighing scale in order to measure that difference. So when it escapes out the top of a conical flask, you'll see the mass decreasing, and you can measure that over time. Equally, you could use gas syringes, and that will show you the volume of carbon dioxide that's released. You can't use this method if you're measuring hydrogen gas because it is too light, so you won't actually be able to see a change in the reading on the measuring balance. Sometimes there'll be experiments involving crosses being obscured due to a precipitate being formed. So you measure the time taken for the cross to disappear. But that's obviously fraught with difficulties because it's very much human judgement as to decide when that cross disappeared. So do be prepared to talk about some limitations related to the methods used. (no audio) So, why are catalysts used in industrial processes? Well, the sensible thing here is to increase profits. After all, people carry out industrial processes to make money by providing useful products that people are willing to pay for, so certainly it's to increase profits. You find the products tend to be made in less time ... and at lower temperatures ... which makes them cheaper. And lastly, they're unchanged, and they don't get used up. So they're unchanged at end of process ... and they don't get used up. Related to catalysts, hopefully you know that enzymes, which we study more in biology - but these are examples of biological catalysts. And so you can use your same definition here: they speed up the rate of reaction without being used up. And how do they work? Well, remember enzymes are made out of protein. They have a specific site on them called the active site. And it's at this active site where you find that the substrate binds ... so that the enzyme can act upon it and later produce the product. And we call the way in which the enzyme and substrate fit together the lock and key theory. So, I thought the easiest way to talk you through the energetics topic was to take you through some past exam questions because they're pretty much all the same. So the moment you see a polystyrene cup and a thermometer, we're looking at enthalpy. So be aware of what endothermic and exothermic means here. So remember, exothermic means 'gives out heat energy', and endothermic means 'takes in heat energy'. And with an exothermic reaction, you're looking for a negative ΔH, whereas endothermic, you're looking for a positive ΔH. Again, in terms of the actual temperature of the beaker or the cup, an exothermic reaction will get hot and an endothermic one will get cold. And if you bear that in mind, hopefully it'll make answering these questions far more straightforward . 'A student uses this apparatus to investigate the heat energy released when nitric acid is added to potassium hydroxide solution.' So we've got nitric acid inside the burette, which is going to be dripped into the polystyrene cup containing potassium hydroxide. 'She uses this method: Put 25cm cubed of potassium hydroxide solution into the polystyrene cup.' 'Measure the temperature of the potassium hydroxide solution. 'Add 5cm cubed of nitric acid from the burette. 'Stir the mixture mix and measure the highest temperature reached. 'Add further 5cm cubed samples of nitric acid. 'Stir and measure the highest temperature reached after each addition.' 'Name the piece of apparatus that should be used to measure the 25cm cubed of potassium hydroxide solution.' So you need a fairly precise piece of apparatus here, which is why you should state either a pipette or a burette; a measuring cylinder would not be precise enough. 'The table shows the student's results.' So here she's got the different volumes of acid and the highest temperature reached. And we can see the highest temperature was reached when the largest volume - 30 centimetres cubed of acid - was added. 'The result for 20cm cubed is anomalous.' 'Suggest 2 possible mistakes, other than misreading the thermometer, that the student might have made to produce this anomalous result.' So remember, anomalous means that it's the odd one out. It isn't quite what you would expect. And if we actually look at those results, it's 31, which is pretty close to 29, so we're thinking that the temperature is too low. So what could have caused the temperature to be too low, aside from misreading the thermometer? Well, first of all, she could have added less than 5 centimetres cubed extra of the acid. Secondly, she might not have waited until the highest temperature was reached. And thirdly, remember when you're doing this experiment, it's really important that you stir the reactants. So she might not have stirred them properly. 'Suggest a true value for the temperature when 20cm cubed of acid is added.' So let's have a look. You kind of want somewhere that sits between 29 and 37, so I'd probably go in at 33. 'In another experiment, a student records these results: 'volume of potassium hydroxide solution, starting temperature of potassium hydroxide solution, 'total volume of acid added and the highest temperature reached by the mixture.' And we're calculating the heat energy released using this equation: Q = mcΔT. So this is really nice; they've given us pretty much all of it. So Q is what we're after. Mass of the mixture - so you need to add those two volumes together, so 25 plus 25 is 50 ... times the specific heat capacity, which we've been given is 4.18, times the temperature change ... which is - we know it goes from 16 to 35, meaning that there has been a 19° increase. And then when you pop that into your calculator, you get a value which is 3970 to four significant figures. Let's have a look at some more questions. So: 'Explain in terms of making and breaking bonds why some reactions are endothermic. Draw a labelled energy level diagram for an endothermic reaction.' So, this is what you need to do. You need to do your axes here. The y-axis is the energy ... and the x-axis is basically the progression of the reaction. So remember, with endothermic, you're looking at a positive ΔH, which means that the products, by definition, must sit at a higher energy level than the reactants. So make sure they are. And then we label them 'products'. We've got our reactants over here. And then just draw an arrow from the reactants to the products, going upwards. So ΔH is positive. 'Use the bond energy data to calculate the enthalpy change of the reaction below, 'making sure to give a sign and units in your answer. 'Draw a labelled energy level diagram for this reaction. 5 marks' Okay. So this is good. If they haven't drawn them out for you like this, you need to see all the bonds. Make sure you draw out that diagram. Otherwise, you'll screw up. So it's so important that if they give you it looking like this instead, like CH4 + 3O2, it is essential that you convert it into a picture like this. So let's have a look at the bonds broken first of all. And so just start by listing the bonds. So we've got CH ... and how many do we have? Well, we've got one, two, three, four. And I do like to cross them off just to make sure I've got them all. Then looking the table, and it's 412. Then we've got one C=C bond ... which is 612. Then we've got three lots of the oxygen, so that's 3 x 496. Use your calculator to add it all up. (typing on calculator) These questions are just about being accurate more than how difficult they are ... so you must check your answer. So that's 3748. Now bonds made. So, be careful here. We've got an O=C bond. And count how many though are there. There are one, two, and then there's a big two there, which means there's four ... times 743, which I've got from the table again. And then again with the O-H, we've got one, two, and then the two again, so it's four times O-H, so four times 463. And that gives us 4824. And then in order to work out this, you need to do 3748 ... take away 4824... to get (-1076) ... kJ/mol to the (-1). Be careful of your units. And that reaction is therefore exothermic because it's a minus. Just to show you how to draw the energy level diagram - really similar to what we did above. Here are our axes. We've got energy or enthalpy on the y-axis. Now, do remember because it's exothermic that our products, therefore, have less energy than our reactants, which is why it's this way round. We know the arrow is going to go down, and it's by (-1076) kJ/mol to the (-1). And then just label your reactants. And you can be really precise here because you can actually see what the reactants are. So I'm just going to write C2H4 + 3O2 is the reactants. And then I can see that the products are 2CO2 ... + 2H2O. (reading visual aid 3) So, this is about accurately reading the thermometer. So before, you can see that it is 18.7°C. The temperature after is 25.3°C, which means that temperature change, once you pop that into your calculator ... (no audio) So, let's look at organic chemistry, one of my favorite topics. So, first of all, organic chemistry, what are we talking about? We're talking about hydrocarbons. So what is a hydrocarbon? It's a compound containing hydrogen and carbon only. Make sure you say 'only' in order to get that second mark. So when we're looking at organic chemistry, we're really looking at different families of compounds. And the simplest family is the alkanes. And I'm going to show you now how to draw out the first four alkanes, and we'll have a look at their general formula. Let's look at how we're going to draw various families of compounds, starting with the simplest, which is the alkane family. Do notice their general formula is CnH2n+2. And you must obey that when you're working on the molecular formula. If we take C4H10 as an example, this is a molecular formula because it shows the actual atoms of each element present in the compound, so it shows that this particular compound has four carbon atoms and ten hydrogens. To make it into an empirical formula, just cancel down those numbers, so it becomes C2H5 because you can obviously divide four and ten both by two. This is, therefore, the empirical formula because it shows the actual atoms of each element present in a compound. And then just to notice, a displayed formula is when you draw out all the bonds, so something like that. So let's start by working out the first alkane. So obviously it's going to have one carbon atom ... according to the general formula CnH2n+2, so substitute in the number of carbon atoms as n, so it becomes C1, and then two times one is two, plus two is four, so H4. Because it looks a bit strange to write the one, I'm just going to erase that; there's an invisible one, so it's CH4. Its display formula looks like this, which is you draw the carbon in the middle ... and hydrogens around the outside, remembering that each carbon atom forms four bonds, each hydrogen forms one bond. And you must remember that to help you draw them. Its name - well, it contains one carbon, which is why it meth-, and it's an alkane, which is why it's methane. So looking at the second one this time, two carbons. So we're going to have C2, and then according to the general formula - two times two is four, plus two is six, so its molecular formula is C2H6. Drawing it out, therefore, carbon's in the middle ... then you've got your hydrogens filling up around the edge, each having one bond and each carbon atom has four. Because it's still an alkane, it ends in -ane, but it contains two carbons, which is why it's ethane. The third one now. So, it's C3. Two times three is six, plus two is eight. H8. 3 carbons in a line. Ends in -ane. It contains three carbons, so it's propane. For four carbons - I ran out of space - so it will be C4H10. And it contains four carbons, which is why it's but-. Still an alkane, so butane. So these are the simplest hydrocarbons, and we call them saturated, and that's because all the carbon bonds are single. If we look at alkenes, they are unsaturated, and that means they contain a double carbon bond (C=C). I'm going to show you how to draw the first four alkenes. Let's now look at the alkenes. And remember they have a general formula, which is CnH2n. Let's first of all start by discussing the functional group of the alkenes. Remember, this is the series of atoms or bonds which makes a particular family of compounds special. So here we see that the alkenes contain a C=C. By definition, therefore, they need a minimum of two carbon atoms to exist, which is why a 1-carbon alkene does not exist. And you have to start with the 2-carbon. So starting with the 2-carbon one, we know we need to substitute two in as the n, so it becomes C2, and then simply H4. The displayed formula - we need a double bond, and therefore, we're going to fill up our hydrogens. Do notice again that the carbons have four bonds, the hydrogen has one. Contains two carbon atoms, which is why it begins with with eth-. It's an alkene, so it's ethene. Looking at three carbon atoms now, so it's C3H6. Again, make sure you're filling these up properly, double-checking the bonds. I can't reiterate this enough. And this will be three carbons, so prop-. It's an alkene, so propene. Now looking at the four carbons, which is when it gets a bit more interesting. So we've got C4H8. And therefore, we can draw the first version of this like this. In terms of its name, it's butene ... however ... we now need to look at the other available isomer. Remember that an isomer is something with the same molecular formula but different structural formula. So if we draw that molecular formula out again - C4H8 - but we try and work out a different structural formula, we can simply shift that double bond along so it now appears in the middle. And now just fill in those hydrogens ... making sure you don't draw too many bonds on those central carbons. And you can see this is still C4H8 ... however, the structures are different ... and therefore these are both isomers. And the way in which we name them is according to where you find that double bond. Because the double bond in the black version is between the first and second carbon, we call it but-1-ene. Because the double bond is between the second and third carbon atom, we call it but-2-ene. So, let's try and work out the various isomers we can draw for C5H12, which is obviously pentane. So let's start by drawing the straight chain isomer straightaway because that's the easiest to do. Because we're drawing isomers, it's likely we need to draw a branched version now, so I'm going to add a methyl group. It needs to be on a minimum of this second carbon along because if you draw it on the first one, it's just like a straight chain isomer, but just going around the corner. You need to ask your chemistry teacher if you don't quite know what I'm talking about there. And make sure we've got five carbons. So I've drawn four. Here's the fifth. Then fill up with hydrogens. And just double-check them. So, we've definitely got five carbons. I've got 3, 6, 7, 8, 9, 10, 11, 12. Yeah. So that's C5H12. Let's work out its name. Well, the longest chain is but-. There are four carbons. We've got a methyl group on the second one, which is why it's 2-methyl-butane. Try not to capitalize that 'b'; I shouldn't have done that. And then let's work out where the next isomer will be. Well, we can't go and add the methyl group on to this carbon instead because that would actually be the same isomer as the one I've just drawn because it's still on the second carbon, but just looking right to left. So I'm just going to have to add another methyl group, I think, off that second carbon, which will look like this. And I do have one, two, three, five carbons, so that's right. Just fill up the hydrogens ... and count them all up. So five carbons. Three, six, nine, twelve. Yeah, that is correct. Right. This is going to be more difficult to name. So, the longest carbon chain has three carbons in it, which is why it's propane. It's propane - 'pane' - rather than 'ene' because it's an alkane; there's no double carbon bonds. And we've got two methyl groups, and they're both off the second carbon, which is why it's 2,2- - there's two of them, so it's di- - and their methyl group, so it's 2,2-dimethylpropane. Now, these families of compounds we call homologous series, and that's just a fancy way of describing a family of compounds. So, what can we say that all members of the same homologous series have in common? So what do all alkanes have in common? What do all alkenes have in common? Well, first of all, they have the same chemical properties, which makes sense. They're going to react in a similar way because they have the same functional group. They're, therefore, going to have the same functional group, which is good because I just said that. They obey the same general formula. So alkanes, for example, will follow CnH2n+2, whereas all alkenes will obey CnH2n. And then they show a trend or a gradual change in physical properties, which again makes sense. So ethane has two carbon atoms, whereas methane has one, so therefore, you'd expect ethane to have a higher melting point and boiling point, which it does. So what is a functional group? Well, it is an atom or a group of atoms which determine the chemical properties of a compound. So, we talked about alkanes and alkenes, but where did they all come from? And they come from crude oil, which is a black, sticky substance which comes out of the Earth's crust, and it has made some people billionaires because this stuff is worth a lot. Why? Because once it has been sorted, once it has gone through fractional distillation and been separated out into various fuels, that can be sold for a huge amount of money. Why? Because fuels are essential for how we run our lives. It's how we heat our homes and how we run our cars. So, what is a fuel? Well, it's a substance which releases energy when burnt. We've talked about crude oil, but how is fractional distillation actually carried out? So we get our crude oil - which we know is a mixture of hydrocarbons - we heat it until it evaporates, and then we pass that vapour into a fractionating column or tower. Now, that fractionating column has a temperature gradient, which means it's hotter at the bottom and cooler at the top. So in terms of these various crude oil fractions - and a fraction is just a group of compounds with similar boiling points - they will condense at different positions within the fractionating tower. So, the longer chains will condense at the bottom, where it is hottest. So, just make sure you learn my summary if you're not following what I'm saying because you'll get all the marks anyway. Now, looking at the top then - which we need to go through the order in which the fractions are condensed. So, refinery gases occur at the top. After that, you have petrol. Then you have kerosene, followed by diesel ... fuel oil, and lastly bitumen. So what are the various uses of these different fractions? Well, refinery gases are bottled gas, which we use in our central heating. Petroleum, or gasoline as it's otherwise known as in America, is obviously used as a fuel for cars. You have kerosene, which is a fuel for aeroplanes. Diesel is a fuel for lorries and buses, so anything big. Fuel oil is used as ship fuel. And lastly, bitumen is used for road surfacing or roof material. I don't know if that's a verb or not, to be honest. but I think it's used to help stick down roofs. I've no idea. Couple of words to be aware of: first of all, viscosity, so that's how readily a fluid flows. Be aware that the more viscous a fluid is, the less readily it flows. So honey is very viscous because it's slow to flow. I like the fact that that rhymed. And water it is very un-viscous or not viscous at all because it runs very quickly. Flammability, obviously that's to do with how readily something sets alight. Volatility is how readily something turns into a gas. So, if we take the various fractions and we make a few comparisons - let's compare the viscosity, volatility, and boiling points of bitumen compared with refinery gases. So clearly, bitumen will be more viscous, it will be less volatile, and it will have a higher boiling point. It will also have a darker colour because it's a brownish sticky color, whereas refinery gases are colourless. So do be aware and do be willing to make comparisons and make full comparisons. So say refinery gases are lighter in colour, have a lower boiling point, are less viscous, et cetera. So once we've got these fuels, what do we need to do to them? We need to burn them. And that's where complete and incomplete combustion takes place. So, complete combustion is when you burn something in a plentiful supply of oxygen, and that means you produce carbon dioxide and water as a byproduct, which is a good thing because neither of these things are toxic, although there are obvious environmental issues with carbon dioxide production due to it being a greenhouse gas. Incomplete combustion is when you have insufficient oxygen, and that means you don't produce carbon dioxide; this time, you produce carbon monoxide and water. So, what are the issues relating to carbon monoxide? Well, it is extremely toxic and poisonous, and that's because it combines with the haemoglobin in red blood cells, forming carboxyhaemoglobin, and that means the red blood cells can no longer transport oxygen around the body. Acid rain now, so we're looking at more environmental issues. So acid rain comes from two areas. Firstly, nitrogen and oxygen in car engines reacts due to the high temperatures found, forming nitrogen oxide. That reacts with water in the atmosphere, forming nitric acid. So there's your first acid rain. Next, crude oil can contain sulfur impurities, and when burnt, they form sulfur oxides. That reacts with water, forming sulfuric acid. So there's your second acid rain. And acid rain gets into lakes and rivers, making them too acidic, therefore killing aquatic animals. It damages trees, and it damages limestone buildings. And you must mention that they're limestone. (no audio) Cracking now - remember that is a process carried out in order to break large hydrocarbon chains into smaller, more useful ones. And it's all due to demand because, effectively, the shorter chained hydrocarbons - the shorter chain alkanes and alkenes - make much better fuels than the long chains, which is why we carry out cracking. Do remember that you need a high temperature which is between 600 and 700 degrees Celsius ... and you need an alumina or silica catalyst in order to speed up the process. Let's touch on a few reactions that you need to be aware of. So, if we take an unsaturated hydrocarbon, so an alkene, and we react it with bromine water - now, you must remember the colour change. What you'll see is it will go from being orange to colourless. And I'll show you the summary equation now. They could ask you, 'What is the test for an alkene or an unsaturated hydrocarbon?' That's actually the same question. So, effectively, you're testing for the presence of the C=C. What you'd write as your answer is that you add bromine water. And in terms of your observations, what you would see is that it would go from orange to colourless. Let's actually look at an example, so we'll take ethene. We're adding bromine water. Remember, bromine is diatomic, hence why I'm saying Br2. And then what happens is the double bond breaks ... meaning that there are two available spaces ... for bromine to join on, which is here and here. And there's no byproduct because of that. And because bromine simply added itself, you say that this is an addition reaction. So, what is the type of reaction? Addition. You add bromine water, and it turns from orange to colourless. Now looking at alkanes' reactions with bromine water - so, alkanes or a saturated compound; it's basically the same thing. What you see this time - I'm going to take methane as my example, but I could have used ethane or propane. We add it to bromine water, but what happens this time is one of the hydrogen pops off. The bromine joins. You complete the rest of the molecule. And what you have left over is clearly a hydrogen that's just left methane and another bromine atom, which is why this is your equation here. Because all that's happened is the hydrogen has simply been swapped or substituted for bromine, we say that this is a substitution reaction. So you can actually see what's happened here. Now we need to look at the Earth's early atmosphere topic. And in order to do that, I think the best thing for us to do is to look at the atmosphere today ... and that will help us understand how the early atmosphere was very different. So, today's atmosphere, hopefully you know, contains 78% nitrogen ... approximately 21% oxygen ... 0.04% carbon dioxide ... and then lastly, small amounts of water vapour and noble gases. But how was the early atmosphere different? And we're looking at, really, 3.2 billion years ago. And in fact, there was very little oxygen. The atmosphere was mainly carbon dioxide. And we think that that carbon dioxide was produced by volcanic activity. So we think that Earth's crust was covered in volcanoes which were belching out carbon dioxide. But how do we know this? After all, no one was around to measure gas composition, so how do scientists actually come up with this? Well, it's through study of other planets and moons within our solar system. (stylus tapping) So by studying ... other planets and moons ... in the solar system. They're particularly interested in Venus and Mars ... because they're incredibly volcanic ... and they have atmospheres that consist mostly of carbon dioxide. They're also interested in Titan, which is a moon belonging to Saturn. It has an extremely high amount of nitrogen in its atmosphere: 98.4% nitrogen. However, it has an icy interior, which we don't believe the Earth ever had. So, we know that the Earth today is mostly covered in ocean, which is why it's often known as the blue planet, but where did those oceans come from? Well, scientists think that water vapour condensed ... so cooled down. And we know when gas is cooled, it turns into a liquid. Next up, why is it unlikely that the Earth's early atmosphere contained oxygen? (stylus tapping) And that's because, as I've already said, it was mostly made up of volcanoes, and volcanoes do not produce oxygen. Secondly, there's lots of a compound called iron pyrite present in ancient rock. And iron pyrite usually gets broken down with oxygen, so the fact that it exists in ancient rock tells scientists that there probably wasn't any oxygen around then. And if you like these sorts of answers, don't forget my revision guide on my website contains - well, it's absolutely chockablock full of them for every single specification point, so visit the online shop at sciencewithhazel.co.uk in order to have a look at those guides. (no audio) Although this might seem slightly out of joint, we now need to look at the effect of excess carbon dioxide on the environment. So remember, carbon dioxide is a greenhouse gas. So, enhanced greenhouse gases - so more CO2 being released - will lead to global warming. Now, global warming causes polar icecaps to melt. Because they've melted, it means that there is a rise in sea level, which floods low-lying land. This obviously causes the destruction of many habitats. It can cause the extinction of species that get caught up in it. And other effects include changes in bird migration patterns - so that's where they fly in the summer and the winter - and also increased extreme weather. (no audio) Oh! We can move away from that disgusting topic now and just look at generic tests. So, the test for hydrogen - don't say it's the squeaky pop test; you won't get a mark for that. You need to say that you hold a lighted splint over the gas, and if hydrogen is present, there should be a squeaky pop. With oxygen, you need to say that it relights a glowing splint. Carbon dioxide, remember, turns limewater cloudy. Chlorine bleaches damp litmus paper. And ammonia times damp red litmus paper blue. Now, I've given you the most concise, precise definitions for this ... so make sure you've learned them. Every single word matters here. So, for example, 'damp' is worth a mark, 'red litmus paper', worth a mark. So make sure you learn them properly. And now we're getting more complex, and we're going to look at flame tests. So remember, if we have an unknown metal ion, a flame test is a good way of working out what that metal was. So, in terms of carrying out a flame test, remember that you're going to use a clean nichrome wire, which is - you could clean it using hydrochloric acid, but the point is you don't want any contaminants on the end of that nichrome wire. Then you dip it in the sample to be tested, and then hold it in a roaring blue flame, and that is key. You can't be adding it to a yellow, sooty flame. That won't work because the yellow will obstruct the colour. So hold it in a roaring blue flame. So, the colours - now, if we've got lithium ions, you will see a lovely red crimson colour. Sodium, you'll see a yellow flame. And potassium, as with when you add it to cold water, you will see a lilac flame. Calcium goes an orange/red colour or a brick red colour. And copper goes a blue/green colour. If you don't want to carry out a flame test, you can use a precipitation reaction and you can look at the colour precipitate formed once you've added sodium hydroxide. So if you add sodium hydroxide to something containing copper, you will see a blue precipitate formed. Iron (II) will form a green precipitate, and iron (III) will be a brown precipitate. And I remember those because they're kind of muddy, earthy colours. So it goes green for iron (II), brown for iron (III). Testing for ammonium ions now, which is NH4+. Again, add sodium hydroxide. You won't see a precipitate form in this case. Instead, a stinky gas will be released, which should be ammonia. And you test for the presence of that ammonia using the method I've already described, which is that it should turn damp red litmus paper blue. Okay, moving over now to the test for negative ions. We've looked at metal ions and ammonium, so we're looking now at the halides, which is Group 7, the halogens. So, first of all, you need to add nitric acid. You add that dilute nitric acid in order to remove any carbonate ions which might interfere with your test. Following that, you add silver nitrate, and then you'll end up with a range of precipitates. So, looking at the chlorides, if you add chloride ions to silver nitrate, you produce silver chloride, which is a white precipitate. If you add silver nitrate to something containing bromide ions, you make silver bromide, which is a cream precipitate. And lastly, adding silver nitrate to something containing iodide ions will produce a yellow precipitate. So notice those colours get darker: we go from white to cream to yellow. And be prepared to write the ionic equation for this, which will be - for example, with chlorine will be Ag+ plus Cl- forms AgCl solid. (no audio) Now we need to look at the chemical and physical tests for water. So the physical test for water is you just need to check a substance's boiling point. If it boils at 100° Celsius, you know you have water. And linked with this, how do you show that water is pure? Well, I've already talked about pure substances having one distinct boiling point, and the same is the case with pure water. The whole lot should boil at 100°. If it's boiling over a range, it tells you it's not pure. Now using a chemical test for water, you want to add white anhydrous copper sulfate. Anhydrous means lacking in water. Once it's exposed to water, it should turn blue, and that tells you that the substance you have is water. (reading visual aid 7.5) Okay. It's literally - you have to look at the bottom bar and have a look and see where the lines match up. This is quite a tricky exercise. But you'll see that the calcium lines, if you look down, match up and also the sodium ions match up, so that's your answer there. (reading visual aid 7.6) So, let's think about the colours that those flames would go for sodium and calcium. Remember, calcium would go a brick red colour; sodium would go a yellowy orange color. These colors are very, very similar, So first of all, state the colours. Say that they're very similar, that they would mix, and therefore, you wouldn't be able to work out the individual colours because you just end up with a kind of blur. Now we're going to look at addition polymerization. And they could ask you to show this as an equation, so I'm going to show you what's going to happen. We are taking a monomer, such as ethene. Got to make sure I pronounce that properly - ethene. This is your monomer, which means it is a small subunit. Because it is an addition reaction, we're effectively going to add lots of them together, which is why we write an n here. That just means you have lots of them. Then we need to draw some big square brackets. You want to break that double bond, as I've done there, extend the bond, and now just complete the rest of the structure. And you write an n here to show that there's lots of them. And this is the polymer formed. And if you were to name them, we know that that was ethene. Because there's many of them joining together we say that the polymer formed is polyethene, which you've probably heard of before and not realized is polythene. And that's used to make cling film and plastic bags, et cetera. Let's take propene now, and I'm going to draw propene like this, just to make it easier to draw the polymer. I hope you can see that that is propene; it is C3H6. Again, that's our monomer. We're going to have any number of them, hence the n. Big square brackets. Break that double bond, and now just complete the atom. Be very careful where you draw your bonds. Make sure those carbons are joining. Extend the bonds out. Draw your n. And this is, therefore, polypropene. This is a harder plastic than polyethene, so it's used to make buckets, windows, et cetera. Let's take a third example now. Again, square brackets. Break that double bond, extend the bonds, and then just complete. And this is polytetrachloroethene. What does biodegradable mean? It means breaking down the substance using microorganisms. And everything these days, we want it to be biodegradable; we don't want plastics hanging around for hundreds of years, which is why it's really good if they say that they're biodegradable. What problems are associated with the disposal of addition polymers, so, really, problems associated with plastics? That is that most of them are non-biodegradable. They are unreactive, which means it's difficult to break them down. And when you burn them - there's a different way of disposing them - they produce lots of toxic gases, so there's no one good way of disposing of addition polymers or plastics because they just fill up your landfills; they don't rot; they don't biodegrade; they're unreactive; and when they're burnt, they give off nasty toxic gases. Do notice that biopolyesters are biodegradable. Now, this next bit's quite tricky. They want you to be able to show how two amino acids may form a peptide bond. So I'm going to bring up an example now because that's the easiest way of describing it. Don't sweat it too much, guys. If you know everything else but you don't know this, you'll still be able to get your grade 9. So don't worry too much. But do be aware that we've lost a water molecule. It's a condensation reaction. And keep an eye out where the bond is formed, and it's formed between the carbon and the nitrogen, and that's forming a peptide bond. Then the syllabus dips into DNA. So remember that DNA is a double helix It's found inside our cells, and it's responsible for our features, for the proteins which we make. Now, in terms of the structure of that double helix, remember, it's made up of a sugar, phosphate, and base, and that base can be one of four things: it can be A, T, C, or G. Remember that A bonds to T and C bonds to G. So the straight letters bond together, and then the curly letters bond together. These are called nucleotides. So, a nucleotide exactly is a sugar, phosphate, and a base. Let's have a look at condensation polymerization right now, which is probably the most difficult part of the spec. So because it's condensation polymerization, that means that when these two monomers react, you're going to end up with the loss of a small molecule, which is water. So, let's have a look at our first monomer. So, hopefully you recognize the alcohol functional group, which is the -OH. You've got two carbon chains, so that's why it's ethane. The alcohols appear on both the first and second carbon, which is why its name is 1-ethane,1,2-diol. Over here on the right-hand side, hopefully you recognize the carboxylic acid functional group, which is -COOH. This is ethanedioic acid: ethane because it's two carbons ... -dioic because there's two of these carboxylic acid functional groups. So, let's try and work out where that water will be lost from. That is the -OH from the carboxylic acid, the H from the alcohol end. So that's where the water molecule will be lost. And then it's just a matter of sticking the two ends back together. Looking at the alcohols now, notice that their functional group is -OH. And do remember that each oxygen atom can form two bonds, while hydrogen, obviously, forms only one. So we'll bear that in mind now. So, starting with the most simple version, which contains one carbon. Its name - one carbon, so meth-; it's an alcohol, so it's methanol. In terms of drawing it, draw your functional group coming off first. I've already told you it forms two bonds when you're talking about oxygen. And then just fill up with hydrogens. And that is methanol. Two carbons now, so two meaning it's eth-, so ethanol. This is the alcohol found in actual alcoholic drinks. So, we need two carbons. Here's our functional group, the -OH. Filling up with hydrogen, so there's ethanol. Three carbons. Three carbons, so prop-, alcohol, propanol. Do notice there is a second isomer of propanol because actually what I've drawn here is propan-1-ol. But there's also propan-2-ol, so we can actually move the position of that alcohol functional group to be on the second carbon ... here ... and then just fill up with hydrogens. Try and draw the hydrogens better than I have. These don't even look like H's. So, how can alcohols be oxidized? Firstly, you can burn them in air, which we would call combustion. So that's burning. Secondly, they just react naturally with the oxygen in air, and that's due to the action of microbes in the air. We call that microbial oxidation. And lastly, you can heat them with potassium dichromate in the presence of dilute sulfuric acid, and that will also oxidize them. So if we're taking ethanol, for example, it will be oxidized to ethanoic acid. So we've taken an alcohol, we've oxidized it, and it has produced a carboxylic acid. Some uses of alcohol aside from use in alcoholic drinks - they can also be used as good fuels and in perfumes, and sometimes you'll see on your perfume bottle, it might say alcohol-free, because many actual perfumes do contain alcohol. Looking, now, at the production of alcohol, you need to know the two main ways, which is fermentation and hydration of ethene. So we need to compare both of these methods for making alcohol. So let's, first of all, look at their raw materials. Hydration of ethene - it's obviously ethene - so that's going to be from crude oil, which means it's a non-renewable resource Whereas, fermentation involves using sugar cane - and using your old-fashioned approach, so using yeast in order to ferment that sugar cane to produce the ethanol. So obviously that uses a renewable resource. In terms of temperature and pressure needed, fermentation, that's going to use low temperatures and pressures. Whereas, hydration of ethene is a very industrial process, so it involves high temperatures and pressures. The type of process involved now - we say that fermentation is a batch process, and that's because you mix together all the reactants, and you leave it for several weeks or months, you remove the alcohol, and then you start again, hence why it's a batch process. Whereas, hydration of ethene is a continuous process because it can just carry on endlessly; as long as you've got the reactants and the reaction additions, it keeps going. Let's look at our reaction equations now. You've got glucose from the sugar cane, so C6H12O6. And it breaks down using anaerobic respiration by yeast into ethanol plus carbon dioxide. And we know carbon oxide can be used in bread making. Hydration of ethene is, as the name suggests, adding water to ethene. So you've got C2H4. You add H2O to it. And that's how you produce your ethanol. Lastly, look at the product produced. Fermentation, obviously, makes a pretty impure product because it's got lots of other things mixed in with it, whereas hydration of ethene makes a pure product. So be aware when they give you an exam question and they're giving you a situation and they tell you what sort of resources are available - whether there's lots of electricity available, that sort of thing - be aware of which method would be better to use. Right. Let's look at the carboxylic acids now. They have a more complicated functional group, which is -COOH. Do notice in the top right corner that this actually looks like a C with a double bond to the O and then a sort of alcohol group coming off the bottom of it. So, one carbon - because it is a carboxylic acid ... we're going to start with meth- because it's one carbon, but it's methanoic acid. In terms of drawing it, draw that carbon, draw the functional group, and now just count up and make sure you've got enough bonds coming off the carbon. So far it has three. We know it needs four, which is why it just needs a single H here. Looking at two carbons now, so that means it's eth-, so it's ethanoic acid. Two carbons next to each other. Here's our key functional group. Fill up with hydrogens where necessary. And that is ethanoic acid. Looking at the three carbon version, so prop-. Propanoic acid. Three carbons in a line. There's your functional group. Fill up with H's. So what is a composite material? It's a substance made from two or more materials which give good properties. (no audio) Already mentioned it, but I'm going to mention it again - what is an alloy? It's a mixture of two or more metals. Why are alloys harder than pure metals? Because they have ions of different sizes. The layers are distorted, which means the layers can't slide over each other, and therefore it's a much stronger substance. What is stainless steel? Well, it's an alloy made up of chromium and nickel, as well as, obviously, steel. (cat bell jingles) Lyra, what are you doing? So, what are the useful properties of stainless steel? Why do we do it? Well, because it's very hard, it resists corrosion, it's very strong, and we can make use of these properties in using stainless steel to make cutlery - lots of cutlery is made out of stainless steel. Check it out next time you're eating. (no audio) Next up, we're looking at glass. So how is glass made? By heating a mixture of sand, limestone, and sodium carbonate. They want you to know how borosilicate glass is made. I have no clue what this is. But apparently you need sand and boron trioxide, and this produces glass with a higher melting point. Thank you so much for watching my video. Well done if you made it to the end. Don't forget you can buy my Science With Hazel perfect answer revision guides on my website. They're available right now at www.sciencewithhazel.co.uk. (music)