let's see how quickly we can cover everything you need to know for AQA chemistry paper 2 this is good for higher ear Foundation Tier double combined Trilogy and triple or separate chemistry too that is topic 6 to 10 that's rates organic analysis atmospheric and resources for short I'll tell you when something is just for triple we're going to be booking it here so pause the video if you need a bit more time to get your head around something you see let's go how quickly a reaction happens is called the rate of reaction any rate is the change in a quantity divided by time in this case that something can be the quantity of reactant used or product formed this quantity could be mass or volume of gas that's usually made anyway they like to stipulate that this technically gives you the mean rate as the rate could be changing over the time you measure but that's true for any measurement over time ever so that's a bit redundant but we'll go with it for now an experiment on this could be reacting hydrochloric acid and sodium thos sulfate in a conical flask sitting over a piece of paper with a cross on as the reaction continues the product form turns the solution cloudy we say that's increased turbidity we stop the timer when we can no longer see the cross from above the flask repeat this at different temperatures and you should see that the hotter the temperature the less time it takes another potential experiment is measuring the volume of gas produced by using a gas syringe that fills up when connected to the reaction vessel a graph to show this would have the quantity on the y- AIS and time on the x-axis it's usually a curve that starts off steeply but then levels out or plateaus which shows that the reaction has completed or we can say reached its end point to find the rate at any time you draw a tangent at that Point Pro tip Turn the page so you're drawing the tangent horizontally that will help you draw it accurately then like the equation says you can take the changing quantity and divide by time up divided by Across the rate of a reaction can be increased by the following increasing the concentration of reactants that are in solution increasing the pressure of gas reactants and increasing the surface area of solid reactants that is crushing into a powder now these three all have this effect because the reacting particles Collide more frequently they come across each other more often increasing temperature does that too due to the particles moving more quickly but there's the added bonus that they also collide with more energy meaning they're more likely to react when they Collide due to activation energy remember your energy diagrams from paper 1 finally adding a catalyst also increases rate as it reduces the activation energy needed so particles are more likely to collide successfully and react of course any catalyst is not used up in a reaction it is not a reactant or product itself reversible reactions are pretty self planetary once the products are made they're able to return to their original reactants the prime example here is the harbor process hydrogen and nitrogen react to make ammonia which can also break down back into the separate gases again more on what ammonia is used for later in a closed system that is no particles or energy going in or out both reactions will continually take place eventually the quantity of particles on both s will reach a point at which the rates of both the forward and reverse reaction will be the same so that means there will be no more overall change in the quantities on both sides remember that's not saying that the reaction is stopped per se it's just that there's no more overall change that is until a condition is changed which will affect these rates later's principle states if a system at equilibrium is subjected to a change the system will adjust to counteract that change sounds awfully vague so let's see what that means in practice there are a greater number of moles on the left than the right of this reaction which means that the reaction take up more space therefore if you increase the pressure of all of these gases we say this favors the forward reaction that is the rate of the forward reaction will increase until equilibrium is once again reached but that will happen when there's a greater proportion of ammonia than there was before we could also say that the position of equilibrium is shifted to the right reducing the pressure would of course do the opposite by shifting it to the left instead concentration follows the same principle when it comes to solutions by the way naturally if you remove molecules from one side of the reaction the position of equilibrium shifts in that direction so more is produced increasing the temperature in essence means it's harder for a reaction to produce heat that means that a hotter temperature favors the endothermic reaction in this case that's the reverse reaction you can also think of it like this an endothermic reaction requires energy being put in so a higher temperature supplies that a colder temperature will favor the exothermic reaction retion in this case that's the forward reaction as a rule of thumb any reaction that involves the breaking down of one reactant ammonia in this case that's going to be endothermic in any reversible reaction if the forward reaction is exothermic the reverse reaction must be endothermic and vice versa time for one of the beasti chemistry topics C7 it's organic organic compounds are those that have carbon forming the backbone of the molecules crude oil can be found underground and is the result of Plankton being buried under water a long time ago it consists of mostly hydrocarbons that is molecules only made up of carbon and hydrogen atoms most of these are alkanes which are chains of single calent bonded carbon atoms surrounded by hydrogen atoms as such there's always twice as many hydrogens as carbons in a molecule plus another two on the ends we can therefore write a general formula for alkanes CN and then h2n + 2 all alkane names end with a whereas the beginning of the name tells you how long the carbon chain length is methis 1 ethis 2 propis 3 butus 4 penes 5 hexis 6 and so on crude oil isn't useful as a mixture of all of these different length alanes so we use fractional distillation to separate them out we heat them so they evaporate and rise up the fractionating column apart from the very longest ones which stay as liquid generally used as bimon on roads the column gets cooler the higher up the gases rise as different length alanes have different boiling points they condense H back into liquids at different heights where they're then collected longer alkanes have higher boiling points because there are stronger intermolecular forces between them which more energy is needed to overcome the shortest alkanes remain as a gas even at the top we call this fraction LPG or liquid petroleum gases because they're put into pressurized containers afterwards to transport and then turn into liquid LPG contains a range of chain length alkanes like all of the fractions Below in LPG case it's up to four carbons long these are the other fractions you need to know petrol is the next longest fraction so it condenses just below LPG that's used in cars of course Kine is used for jet fuel then diesel oil cars and lorries and things and heavy fuel oil is used in large ships as you can see these alkanes can be burned as fuel you should remember that complete combustion with oxygen produces carbon dioxide and water you know about their varying boiling points but you also need to know that longer fractions are more viscous or have higher viscosity it's just a sciencey word for more thick and gloopy and shorter fractions are more flammable easy to burn but these different fractions can also be used to make solvents lubricants detergents and perhaps most importantly polymers used for Plastics polymers can be made from alkenes but not alkanes an alen is a hydrocarbon that has a carbon carbon double bond in by the way we can call this C double bond c a functional group because of this double bond we can also say that this molecule is UNS saturated whereas alkanes are saturated which essentially means that they're full that's why you can test for an alken which is a colorless liquid by adding bromine water which is orange if the mixture turns colorless that means that the bromine has bonded to the alken for example it bonds to ethine by breaking that double bond into single bonds used to attach the bromines the proper name of this product by the way is one two dibromo ethane and this is saturated as you can hopefully see this can't happen with an alkane as it's already saturated of course so it stays orange chlorine and iodine react in a similar way and water can also saturate an alken by attaching itself as an h and an O functional group we've now made an alcohol by the way more on this for triple in a bit now there are two more problems with crude oil one is that the demand for shorter alkanes is much higher than that for longer ones also there aren't enough alkenes in it for our purposes cracking solves both of these problems that is breaking apart a longer alkane into a shorter alane and an alken catalytic cracking requires a temperature of around 550° c and a catalyst called a zeolite if there's no Catalyst you can just use an even higher temperature of over 800° which makes sense doesn't it this is called steam cracking let's take butane and crack it it can split right down the middle but there must be the same number of all atoms in the product that means that yes we make ethane but there's not enough hydrogen to make another ethane so instead it makes ethine as well the alken which of course is then useful for making polymers it could also split here instead to make methane and propane cracking allows us to meet the demands for shorter alkanes for fuels as well as produce alkenes for making other materials moreon polymerization for triple in a bit the rest of organic is just for triple so skip to chemical analysis if you're doing double like we mentioned earlier an alcohol is an organic compound with an O functional group their names always end with all so this is ethanol these can react with oxygen that is comust to make carbon oxide and water if it's complete combustion and carbon monoxide or carbon and water if it's incomplete combustion When there's less oxygen available reacting ethanol with sodium makes sodium ethoxide and hydrogen similarly for propenol and butanol just one of those random bits you need to know short alcohols like these can mix with water to produce a solution which gets more difficult as they get longer when an alcohol is oxidized without combustion that is with an oxidizing agent it makes a carboxilic acid that's a molecule with instead of Co it's co that's the functional group it still has the hydroxide the O group but it's not an alcohol anymore the name of this would be ethanoic acid we can also get propenoic butanoic acid Etc polymers are super longchain alkanes made up of repeating sections made from monomers poly just means Lots mono just means one for example lots of ethenes the monomer can be joined together through addition polymerization to make polyethene or polythene that's the polymer these monomers must have a double bond in note that even though it makes a long alkane we still use the name of the alken it's made from it's polyethene not poly ethane as you can see this happens because the double bond split so a carbon can bond to the next monomer and so on thankfully we only have to draw the repeating unit with brackets around it and the bonds coming out with an N on the outside showing that there are lots of these joined together condensation polymerization is when we join together two monomers that have two functional groups for example an alcohol and a carboxilic acid first let's look at the reaction between ethanol and ethanoic acid these can react to produce ethy ethanoate this is an Esther can you see water must also be produced now let's react an alcohol with an O on both ends and a carboxilic acid with Co on both ends too now this reaction happens on both ends and we can make a chain of this Esther this would then be a polyester it doesn't matter what's in between the functional groups we can sometimes just write r as a shorthand for the stuff in the middle or just a we box the process is the same every time again water is chucked out hence why it's called condensation polymerization you should remember amino acids from biology they're the building blocks of proteins they have two functional groups an amino group nh2 and a carboxy group Co which we just saw hence why it's called an amino acid these can be polymerized to make poly pepti Ides joining together different amino acids makes a protein DNA full name deoxy ribonucleic acid is the large molecule that stores genetic code it's made from two polymers that spiral around each other in a double helix and it's made from four different monomers called nucleotides starch is also a natural polymer where the monomer is glucose and cellulose is a polymer that's made from beta glucose and like we've just seen proteins have amino acids as their monomers C8 now chemical analysis how can we tell what chemicals we have in front of us obtaining pure substances is very important when it comes to chemistry one way to tell if a substance is pure or not is by testing to see what its melting point or boiling point is if it's pure it should be a very specific temperature a formulation is a mixture that has been specially designed to be useful in a very specific way with very specific quantities of different substances used to make things like paints fuels Alloys fertilizers think of George's Marvelous Medicine as being the ultimate formulation chromatography is a way of separating substances in a mixture for example pigments in inks or drugs in a urine sample the stationary phase often special chromatography paper or just filter paper is what the substances move up with the help of the mobile phase often just water which Rises up the paper due to capillary action dragging lighter particles further up the stationary phase we draw the line at the bottom in pencil so it doesn't move with the solvent the water then at the end of the process we measure how far the solvent has moved and also how far the substance or substances have moved too and these are both measured from that starting line we can then calculate an RF value that stands for a retention factor which is just a ratio of how far a spot has moved compared to the solvent so that ends up being a number between zero and one we can compare RF values of our spots with known RF values to identify what's in our mixture we can test for hydrogen by holding a burning splint over the test tube which will produce a squeaky pop oxygen will relight a glowing splint carbon dioxide will turn lime water cloudy when bubbled through it chlorine gas will bleach damp blue litmus paper that means turn it white we can test for some metals with flame tests lithium will produce a crimson flame sodium yellow potassium lilac calcium orange red and copper green we can test for other metals in solutions by adding sodium hydroxide aluminium calcium and magnesium in solution will produce a white precipitate however the aluminium hydroxide produce will then dissolve if excess sodium hydroxide is added copper 2 ions that is cu2+ ions form a blue precipitate Ion 2 green precipitate ion 3 Brown you might have to complete an ionic equation for these for example the copper and hydroxide ions making copper hydroxide and you got to make sure it's balanced too just three quick ones carbonates react with acids to make carbon dioxide gas and we know how to test for that we test for halide ions that's hogen ions by mixing with silver nitrate solution and nitric acid if chlorine ions are present silver chloride is made that's a white precipitate silver bromide is cream and silver iodide is yellow finally sulfate ions will produce a white precipitate when mixed with Barum chloride and hydrochloric acid of course all of these are chemical tests we can do in our school Labs but in proper Labs with lots of money they use instrumental methods to determine what substances they have these instruments are accurate sensitive and fast for example they can do flame emission spectroscopy flame tests on steroids the light produced by a flame is passed through a spectroscop which can identify exactly what wavelengths are being emitted say on an emission line Spectrum which can then be used to identify these metal ions atmospheric chemistry the composition of gases in the atmosphere has changed over the course of the Earth's history of course records only go so far so we have to extrapolate to get an idea of what it used to be like but as be usual historical science can't be tested so it's pretty much just a good guess to begin with it would have just been a lot of nitrogen and carbon dioxide this then probably dissolved into the oceans which were the cells probably a result of water vapor from volcanoes condensing this carbon dioxide could have then been trapped in sediment rocks and fossil fuels reducing the carbon dioxide in the atmosphere algae and plants turn CO2 into oxygen through photosynthesis reducing the levels of CO2 to 0.018% which is what we have today water vapor carbon dioxide and methane absorb longer wavelength radiation and keep the earth warm without them we'd freeze this is the greenhouse effect CO2 levels have increased since the Industrial Revolution ution which some think is responsible for the increase in global temperatures I'm old enough to remember when the term carbon footprint entered the mainstream in the mid 2000s when everybody went mad for it the idea that everything you do is responsible for carbon dioxide being released into the atmosphere and that we should reduce that or offset it by planting trees for example carbon monoxide is an atmospheric pollutant it binds to your red blood cells so less oxygen can be transported around your body it's also odorless and colorless so it's hard to detect that can prove fatal most fossil fuels release sulfur dioxide when burnt which causes acid rain nitrogen oxid can also be released which can cause breathing problems s is just particulates of carbon made from incomplete combustion which can also cause health issues it's everybody's favorite final topic full of random stuff literally C10 is using resources we need resources for warmth shelter food and transport some are natural like food wood for building fuels for burning and materials for making fabrics and clothing as demands for these increase we're trying to find new materials to use to help meet these doing so without compromising future Generations abilities to do the same is called sustainability if you like me you probably take clean drinking water for granted but many people around the world don't have that potable water is what we call water that has low enough levels of salt and microbes that it's safe to drink in most countries water is taken from a fresh water source so little salt is dissolved in it is passed through filter beds to remove large insoluble particles then sterilized to kill microbes usually using chlorine but we can also use ozone or UV light in some countries there are few or no freshwater sources so they must get sea water and remove the salt this is called desalination which can be done through distillation but also by using special membranes that employ reverse osmosis however both of these require a huge amount of energy potable water isn't pure water of course in fact Pure or distilled water is dangerous to drink in large amounts as there being nothing dissolved in it water will move into your cells due to osmosis and then become turgid going to the top toilet creates waste water as do industrial processes therefore needs to be treated before being released back into the environment which requires removing organic matter microbes and harmful chemicals we can do this with screening and grit removal sedimentation to produce sludge and effluent we can then treat them separately sludge is the solid stuff that sinks to the bottom which needs anerobic digestion to treat whereas the liquid eement from the top requires treatment with aerobic respiration extracting metals from the earth is a huge industry we use them for electrical appliances batteries for building and more most metals can be obtained from their ore after mining by electrolysis or displacement reactions a couple of new ways of extracting metals are being developed especially for copper as we need a lot of it for say electrical wiring phyto mining uses the fact that plants absorb minerals from the soil into their Roots grow a crop in an area with copper rich soil then burn the plants to be left with copper in the ash bioleaching uses bacteria that make leachates solutions that contain metal compounds and we can get the metal from those both of these ways are pretty terrible though as they yield incredibly small amounts of the metal an LCA or life cycle assessment is the thought process carried out in order to predict a new product's impact on the environment you need to consider a few things extraction and processing of raw materials manufacturing and packaging its use over its lifetime disposal at the end of its life then Transportation at each of these stages too we can reduce our impact by reducing the use of products in general we can reduce the materials needed to make them the energy required and also the waste produced we can recycle materials to reduce our impact too Glass and Metal can be recycled pretty much infinitely although energy is required to do this but the impact on the environment is less than what it would be if we just obtained these raw materials from the earth corrosion is when materials are destroyed slowly over time by chemical reactions for example Iron and steel rust when the iron reacts with oxygen and water other metals corrode in a similar fashion like the copper Statue of Liberty now green copper oxide on the outside we just reserve the term rust exclusively for iron we can coat a metal with a more reactive metal that corros before the other we then call that a sacrificial metal zinc is an example coating a sheet of another metal with this is called galvanizing Alloys are mixtures of different Metals bronze is an alloy of copper and Tin prass copper and zinc even gold jewelry isn't usually pure gold it would be too soft it's combined with silver copper and zinc 24 Karat is 100% gold 18 karat being 75% Etc steel is an alloy of iron and carbon which makes it stronger than pure iron if it contains chromium or nickel it's a stainless steel which is more resistant to corrosion Alloys are usually stronger than pure metals because the different size atoms disrupt the regular latice which means the layers cannot slide over each other as easily aluminium is used in an alloy when we need a low density most glass we use is soda lime glass made from Heating sand sodium carbonate and Limestone boros silic glass on the other hand has a higher melting point Ceramics like pottery and bricks are made from clay which are then heated in a furnace Composites are materials made from two materials usually that involves fibers of one material being binded or bound together with another an example of this is carbon fiber very strong yet light polymers can be high density or low density for example you might see hdp or ldpe on Plastics they stand for high and low density poly eth the difference depends on the conditions used when making them thermosoftening polymers melt when heated whereas thermos setting polymers do not melt no matter how hot they get the difference is that there are these cross links between the polymer chains that are formed when a thermos setting plastic is made that increases the forces between them holding them together like we saw at the start the harbor process is used to make ammonia which can be used for fertilizers nitrogen can be easily taken from the air whereas hydrogen can be obtained from electrolyzing water the gases are passed over a catalyst at around 450° c and a pressure of 200 atmospheres like we saw with l chatellier a high pressure favors the forward reaction however we can't have too low a temperature otherwise the rate of reaction will be too slow so that 450° is a compromise to balance yield and rate of reaction the ammonia produced is removed and the unreacted nitrogen and hydrogen are recycled ready to make more ammonia plants need nitrogen to grow which is why we use ammonium and fertilizers but they also need phosphorus and potassium therefore many fertilizers are n PK fertilizers the ammonia is first used to make ammonium salts to go in the fertilizer potassium chloride and pottassium sulfate are obtained by mining as is phosphate Rock which needs to be treated with an acid first to produce a salt before going into the fertilizer that's it I hope you found that helpful leave a like if you did pop any questions or comments below and hey after you've done the exam why don't you come back here and tell us how you found it we'd love to know click on the card to go to the playlist for all six papers if you need some extra help follow the link in the description to join our Discord and I'll see you in the next video good luck