the entire of GCSE CHEMISTRY paper 2 (taught by a medical student!)

Added: 2026-06-04

[00:00:00]Okay, we are on with GCC chemistry paper 2, a highly requested video where we're going to go over everything in this video. I got a grade nine in GCC chemistry. I got a grade A sadly in A level chemistry and I got into med school from there and I learned loads about chemistry in med school and I really enjoy it. It's my favorite topic out of all of the GCs and A levels. So without further ado, let's get going. So paper two, topic six, we're on with rates today. Rates are to do with how fast a reaction occurs. Rate by definition is we say 1 /x. That basically means how fast something happens in a given amount of time. Okay, don't worry about that though. So rate of reaction we're going to have obviously the x-axis here the independent variable. I change on purpose the thing you change and the yaxis x to the left y to the sky. Y-axis is the dependent variable. It depends on the thing you change. So you measure it.

[00:00:51]We're measuring the amount of product forms. Here we have four reactions.

[00:00:54]Reaction number one has a very slow rate of reaction. How do we know? Because of the gradient. Gradient is how steep a reaction is. The rate of reaction is the gradient. The same damn thing. Number two has a greater rate of reaction.

[00:01:07]Number three even more. Number four the most. But rate of reaction changes.

[00:01:10]Remember it's 1 /x. X depends on where you're measuring it. The rate of reaction here isn't as much as the rate of reaction here because the gradient is less. How do you work out gradient then?

[00:01:21]Gradient is simply dy by dx. This literally means, don't worry if you don't know what that means. It means change in y over change in x. What does that mean? I'm glad you asked. Let's say we wanted to work out the gradient of this point here. What you need to do is draw something called a tangent. And a tangent is a straight line that only touches your curve once. Now, you're going to need to plot coordinates.

[00:01:43]Remember, x comes first, then y. Take two coordinates. Let's take one here, and let's take one here. Let's pretend this is number one. This is number two.

[00:01:51]At number one, let's say x is going to be five. So it's going to be five, comma, let's say y is 20. Okay? And then let's say for coordinate number two, x has gone a lot longer. So let's say x is 20 and y is y is also a lot higher. So let's say y is 25. You need to do dy by dx, which means the change in y over the change in x. So let's call this x1 y1 x2 y2. Change in y over change in x. 25 - 20 change in y over 20 - 5 and that's that's your gradient that's your rate of reaction that's all you need to know but seriously try and learn how to do tangents it will come up this okay right next then on this topic is the rate of reaction being determined by the number of successful collision so I've said rate of reaction is gradient and rate of reaction is also the number of successful collisions in a given amount of time so four things affect the number of successful collisions in a given amount of time please remember This one of them is temperature. So we increase temperature, kinetic energy goes up, more successful collisions. In the exam, you need to end it by saying more successful collisions or less successful collisions depending on what the question is asking. You need to use a terminology though. Please do. Next one then is surface area. Greater surface area, more chance of contact, success, more chance of good successful collisions or successful collisions, greater rate of reaction. That's all you need to know. Explanations here. Learn this. Next one's concentration.

[00:03:13]Concentration is a measurement of how much liquid how much things in a liquid there are. Concentrated orange juice has a lot of orange juice in the liquid, not a lot of water. In the same way in chemistry, something really concentrated has lots of dissolved substance in it.

[00:03:26]So they're going to be more successful collisions if it's more concentrated, greater rate of reaction. Finally, a catalyst. Okay, there's an idea called activation energy. And activation energy by definition is the minimum amount of energy required for a successful collision to occur. If we have a catalyst, it lowers the activation energy. Meaning less kinetic energy is needed for a successful collision to occur. It's a bit like pretending you wanted to boil some water and you added some kind of some kind of thing that made water boil quicker. It takes less activation energy for that reaction to occur. That's all you need to know.

[00:04:00]That's what a catalyst does. So a catalyst means less energy is needed for a sex of collision. Therefore, it's going to be quicker, greater rate of reaction. Please learn all these four.

[00:04:08]You get asked to apply them quite often.

[00:04:10]Next up then is how do we measure the rate of reaction? This is all about rates. How do we measure rate of reaction? There's three ways. Um, and these two are the best ones and this middle one's the worst one. I'm going to talk about them briefly. Using a gas syringe. Basically, when the product is a gas or there is a gas in a product, you can use a syringe and it obviously inflates as you use a gas. And the more gas that's been made, the more it will inflate. That can determine the rate. So let's say we have like a beaker here and then we have a tube and a gas syringe like that.

[00:04:42]If this bung gets pushed by really fast, we know loads of gas is being made. High rate of reaction. This can only be used though obviously if a gas is being produced. So be really careful when you read the state symbols. There must be a little G meaning a gas is made. If no gas is made, you can't use this. You can't work with it. Okay. So the next one is going to be the precipitate/color change. So for this one basically a precipitate is a insoluble solid. So this is either going to appear or disappear depending on the nature of the reaction. The problem with this is a subjective to your eyesight. If I let's say a color was going to form and it formed let's say at 20 seconds but I thought it was 22 seconds. It's just subjective depended on our eyesight and our vision. It might be a color change.

[00:05:24]My pink might be different to your pink.

[00:05:26]It's all subjective. That's a limitation of this but it's easy to do. Final one is mass change. Once again, if a gas is released, it might go be released into the atmosphere and therefore you lose some weight. You can measure that weight loss using a mass balance. Okay? And here's one of the benefits of that. Give this table a read. Learn it. Next then in rates is equilibrium. Okay? We've only covered forward reactions.

[00:05:46]Reactions can also happen backwards as well. Okay? Yes, they can. It's amazing.

[00:05:50]Um it's pretty cool fact, right? So we have this thing called equilibrium which is basically when the rate of the forward reaction and the rate of the backward reaction are constant. Not the same, but constant. And basically reversible reactions will always reach equilibrium in a closed system. Remember rate of forward rate of backwards are constant. Okay? And it's something called lashilia's principle. These systems here will always try to keep the say the same. So for example this here if let's say it takes in energy as this reaction occurs energy is taken in. If we if we change the temperature of the system this system here this equilibrium will do everything it can to decrease the temperature and bring it back down to equilibrium. In the same way, if we increase the pressure, this equilibrium will try and decrease the pressure.

[00:06:33]Don't worry too much about it. Just know that's Latitilia's principle and equilibriums oppose change to bring it back to equilibrium. A dynamic equilibrium does that. It's amazing.

[00:06:42]Okay, read up more on that if you don't really get it. That's all of rates done.

[00:06:45]Look at that. We are flying through this. Next one then is organic chemistry. So, organic chemistry refers to one beautiful element, carbon. Carbon is organic chemistry. Let's talk about it. This is concerned about hydrocarbons. So you need to be able to define a hydrocarbon. Believe it or not, it's in the name hydro hydrogen carbon carbon. These are molecules containing only hydrogen and carbon. Learn that. It comes up all the time. Very high yield.

[00:07:11]Next then we have types of hydrocarbons.

[00:07:14]First is an alkan. So we have something called a general formula. All alkanes follow this general formula. CN H2N + 2.

[00:07:27]What this means is let's apply the number N to any given number. So let's say N equ= 1. So it's going to be carbon * 1 plus hydrogen 2 * 1 + 2 which is going to be C H4 or methane. Okay. So methane is our first hydrocarbon, our first alkan. Okay, CH4. And it looks if go do the displayed formula like this.

[00:07:53]Why? Because carbon is the fourth in group four. Group four elements have four electrons on the outer shell. They can have eight max. So it goes 5 6 7 8.

[00:08:03]Carbon's happy. Okay. Remember something called honk. This is how many times these organic elements can bond.

[00:08:09]Hydrogen needs to bond once, oxygen twice, nitrogen three times, carbon four times. Remember this. It's quite important and useful when you draw a displayed formula. Methane is our first organic molecule. There's one called ethane. And now if you do C 2 C * 2 H2 * 2 + 2 is going to be C2 H6.

[00:08:28]You need to know how to apply the general formulas. That's ethane. Then there is propane and butane. Learn them in your own time. They are hydrocarbons.

[00:08:36]Okay. Then there's something called alkenes. Alkenes are slightly different.

[00:08:39]The ones I've talked about here are known as saturated hydrocarbons. If something is saturated, that means it is covered in. Saturated hydrocarbons are covered in hydrogen atoms. Unsaturated hydrocarbons aren't covered in hydrogen atoms because they have carbonarbon double bonds like this molecule here. It is not saturated in hydrogen because there is this carbonarbon double bond here. By definition, that is what an alken is. Alkenes have a general formula CN H2N where N can be any given number.

[00:09:11]In this case, N is two. They are named a bit differently. This one here is E and it's going to be E, not Ethane, ethine because this is an alken. You're going to get propene and butine as well. Okay, that these are unsaturated hydrocarbons.

[00:09:26]And both of these have we call these homologous series. So alken homologous series is basically like molecules and compounds that react similarly. If something's in the same homologous series, they react similarly. So alkenes generally react similarly and alkanes generally react similarly. That's what you need to know about that. Now we're on to a bit more of the properties of hydrocarbons. So hydrocarbons vary in chain length massively. I've mentioned something like methane which is CH4. And this is a really short chain. Ethane CH3 CH3 is only a twocarbon chain. But you can get ones with like 20 30 even 40 carbon chain lengths. Really really long. And the properties change with the chain length in general. Think really long chains are going to be sticky, more solid, high boiling points that hence why they're solid. Going to burn really badly. Low chain ones are going to be gaseous. Boil obviously boil and melt really easily because they're a gas at room temperature. Flammable. So let's consider both of these then. Short chain hydrocarbons more volatile. Volatility is a measurement of reactivity. Think of these. Methane is a gas. You use it on buns and burners. Ethane can be used in gas cookers and patio cookers. These are all volatile and react easily. Longchain hydrocarbons. I want you to think of tarmac. The hydrocarbon is called bitumen. Okay, bitumen or bitumen is basically what tarmac is. Tarmac is not reactive at all. You see it on the roads. It doesn't react. It's pretty dull, right? But believe it or not, these are made from the same chemical compounds, just different chain lamps.

[00:10:51]These are less viscous obviously. And then longchain hydrocarbons are more viscous. Think of once again tarmac. It kind of is like a liquid, but it pours terribly. Viscosity is a measurement of fluidity. Something that's very viscous is like honey or syrup doesn't pour very well. Next one then, flammable. Think of gas cookers. And then these are less flammable. And finally, short chains burns with a clear flame. Long chain does not burn with a clear flame. That doesn't come on very often, so don't worry too much about that. Okay, we can do something called cracking. Um, and basically cracking is when you break down large chain hydrocarbons into smaller chain hydrocarbons that are more useful. So, as you can see here, I've already said like these are short chain hydrocarbons are flammable, more reactive. They can be used in like engine or petrol, fuel oil, all that.

[00:11:35]It's a lot more it's a lot more useful than let's say like tarmac. I know tarmac is useful but it's not as useful as these smaller ones and like plastic can be made from small ones as well. So we can do something called cracking which is when we break down large chain hydrocarbons into smaller ones which leads us on then nicely to something called fractional distillation using crude oil. So crude means impure and oil means obviously oil. So when we drill oil from the seabeds, we get impure oil or crude oil which is a mixture of hydrocarbons, okay, of hydrocarbons and it also has impurities within it as well, such as sulfur impurities, which is why it's bad when we burn them. More on that later. Long story short, crude oil, you put it here and you heat it.

[00:12:13]Further down in the fractionating column is going to be really hot. Further up is going to be not so hot. So the not so remember short chain hydrocarbons can boil and melt really easily. So at the top that's where they form because it's not very hot and you're going to get things like methane, ethane, propane, butane. Further down is hot. This is where you get the things that can't boil very easily or melt very easily like tarmac which is also known as bumen. So you're going to get this really far down here. You see ashphalt just there.

[00:12:40]You're going to get fuel oil a bit further down as well. That is all you need to know about fractional distillation. And you need to know at the top is short chains, the bottom is long chains and know some uses for each at each little step because sometimes you get diagrams and you have to fill them in. So learn this here.

[00:12:56]And look at that guys that is organic chemistry done. Very very straightforward. Next is chemical analysis. This is needed to know what things are. This is kind of easy this topic so I'll rush through it. Okay.

[00:13:07]Purity is a like a chemical or a molecule or a compound in its natural state. So water, pure water is H2O. This is also known as distilled water. It's only H2O. Drinkable water that we get from a tap is known as portable water.

[00:13:24]This isn't just pure H2O.

[00:13:27]This is going to be H2O with things like this fluoride ions, chloride ions, probably a bit of sodium, maybe a bit of bicarbonate. There's going to be there's going to be loads in water, but it's still drinkable though, but it's not distilled pure water. This is portable water. Okay. When we test for purity, we need to basically you boil the thing you're testing for and you compare that boiling point, the one you got obviously to the textbook values. For example, if I was to have a sample of water and I wanted to test if it was pure or not. If I boiled it and water boiled at 120° C for me and I open the textbook and it says, okay, water should boil at 100° C.

[00:14:00]This says this is impure brin because it is impure. When there's impurities, it doesn't boil at textbook values. You need to know that. It does come up quite often. There's something called formulations which is basically the exact amount of chemical in each mixtures. That's all you need to know for that. Okay, we need to know tests for four gases. Number one is chlorine.

[00:14:17]This is a H hallogen in group 7 Cl2.

[00:14:20]It's diatomic. We did that last video link up here. Right, chlorine can be tested for by adding litimus paper. LMUS paper and it bleaches it or turns white so it bleaches litmus paper.

[00:14:32]This is a nice two marker. Learn it.

[00:14:34]Next one is oxygen. Oxygen, remember, is used in combustion. If you put a glowing splint or like a wooden piece into the end of a test tube containing oxygen, oxygen allows combustion. It will reignite it. Next one then, hydrogen is known as a squeaky pop test. You light a splint, put it in a test tube of hydrogen, and it goes like pop. That's all you need to know. And this one here for CO2, carbon dioxide. You bubble carbon dioxide through lime water and it turns it cloudy. Okay, that's all you need to know for these four. Bleaches litmus paper reignite. Squeaky pop turns cloudy. Next is chromatography.

[00:15:05]Chromatography is a method to see what substances are in other substances kind of. That's the best way to describe it.

[00:15:13]So ink is a great example. In ink, you're going to have many colors within it. And you want to see how soluble each of these solvents are. Okay? So the way we do this is we this is a really really important practical. So I'm going to talk about it for a bit. You basically put the ink spot onto a piece of paper and then you want to dip the paper into a solution. But the really really key, you don't want the solution to be above the ink spot entirely because it will rub the ink spot off, but you don't want it to like not be touching it at all. So you want the solution to be drawn up, but you don't want it to completely cover it. So just like this diagram here shows, the solution is below the black dot, which is exactly what we want because if it's if it wasn't submerged in it at all, nothing would be drawn up.

[00:15:52]If it was completely submerged in it, the ink would wash off. You need to draw a reference line here in pencil. The reason you need to do it in pencil is because if you did it in pen that would be absorbed and taken up or it would just rub off. Pencil doesn't rub off. It doesn't interact with water. And that's all you really need to know for that. So these these are the ones here. That's and read that. Pause the video. Give that a read. Okay. There's something called RF value. And the RF value is the distance moved by the substance. So let's say the red substance here divided by the distance moved by the solution.

[00:16:22]This here. So let's say about 6 over 10 cm. RF value is always between one to zero and it has no units. This is a simple two marker question. So, make sure you learn how to do RF value. You have to learn that. Remember, it's a quick note. If you like the scrubs you see in the video today and you want to pick yourself up a pair cuz you're thinking of starting med school or some healthcare related course in college or after college, then head over to Nila Scrubs, that's N I L A Scrubs, and go pick yourself up a pair and even get 10% off using code bin 10 in the checkout.

[00:16:54]So, thank you to Neil Scrubs for sponsoring this video. Wow. Wow. Wow.

[00:16:57]That all of that done. Now, we are on with evolution in the atmosphere. Quite an interesting one. This this is topic nine and chemistry in the atmosphere.

[00:17:04]So, we need to know about the phases of like Earth's history. This is like ages ages ages ago. So, phase number one, basically the Earth is really, really hot. We have all of these volcanoes and they are spewing out tons of lava molten and in addition CO2. The majority of the earth in the first stage is CO2 alongside NH3 which is known as ammonia, H2O obviously water vapor, nitrogen which is N3 and methane CH4. By the way, this is a greenhouse gas. Methane, water actually is a greenhouse gas or water vapor and CO2 is a greenhouse gas. More on that later. Next is phase two. We absorb the CO2. Remember the atmosphere is full of CO2. We need to absorb all of this. Now currently CO2 makes up a tiny amount of the atmosphere's gases less than 1%. Primarily right now you need to know these two because it comes up quite often. Our atmosphere is made up of majority of nitrogen and some oxygen.

[00:17:59]Okay, we the high CO2 was brought down because algae and plants photosynthesize. If you don't know what photosynthesis is, this is when plants use carbon dioxide and sunlight to make energy. So we go CO2 plus H2O makes C6 H1206 which is glucose and um oxygen. It releases oxygen. They have to do a balances 6 six and six. So basically plants took in CO2 and released oxygen. Over time CO2 decreased to what we have now. And this is exactly why um trees are like good for the climate because it takes in CO2 and releases oxygen. Water vapor from volcanoes. Remember water vapor is one of the things that's released. This condenses which is the opposite of boiling. So it forms a liquid and basically it can rain, oceans can form and we can have more complex life as well. Plants will have CO2, plants have the sun, plants can literally live and flourish. It's a good time for plants in phase two. Then phase three, oxygen is made. How? From photosynthesis.

[00:18:55]Photosynthesis increases, CO2 decreases, oxygen increases. We have photosynthesis happening. Plants need CO2 for photosynthesis. But remember plants also respire. So they need oxygen and we need oxygen as well. But this led to the atmosphere as we have today which remember is 20% oxygen, 78% nitrogen and a fractional amount of CO2 and helium and other gases in the atmosphere. Okay.

[00:19:19]Greenhouse gases, we need to get this down. Greenhouse gases is a term to describe gases that enhance the greenhouse gas effect. Okay, the greenhouse gas effect is normal. It talks about like Earth's climate being like a greenhouse. So green houses take sunlight in and trap the heat in there so plants can thrive and grow. There are three greenhouse gases CO2, H2O and CH4 or CO2, water and methane. These three trap sun's the sun's heat in okay or u radiation heat in the form of radiation. Okay, basically the sun shines on the earth. Most of the earth reflects it black but greenhouse gases stop this. Let's draw the earth here.

[00:19:58]The sun is shining down here and then we have the atmosphere. most of it is reflected but then there's some gases like CO2 which absorbs this and it causes the greenhouse gas effect to be enhanced. Okay, so you need to say enhanced though. These don't cause the greenhouse gas effect is normal. They don't cause it. They just enhance the greenhouse gas effect. Remember we have natural amounts of CO2 and methane and water in the air. But burning fossil fuels, let's say CH4 plus O2. If we burn methane like we do in school labs, it makes CO2 plus H2O. If we're to balance it, you do a two here and then that's balanced. Fine.

[00:20:38]Here we are releasing CO2 which is a greenhouse gas. We're enhancing the greenhouse gas effect. Okay. Right.

[00:20:44]Greenhouse gas. So the enhanced greenhouse gas effect leads to climate change. Climate change obviously is the climate changing and this has some sad negative consequences such as extreme weather and also just increasing temperature. The weather has been beautiful in the UK right now. I'm sure you're aware. And that is, you know, a product of the greenhouse gas effect. It doesn't affect us as much, but it does affect some things like polar bears and melting ice. So that's one of the things and consequences of the greenhouse gas effect and the climate change being enhanced. [music] Finally is carbon footprint. A footprint is basically like how much you do in your lifetime of something. So the carbon footprint is a measurement of how many greenhouse gases something or someone emits over a given time. And it's basically super duper difficult to measure. So let's say like um you fly tons and tons of airplanes in your lifetime you have a really big carbon footprint. If you eat no meat and you don't travel, you don't drive, you have a low carbon footprint. It's just a measurement of how much carbon you use in your lifetime. Okay, now we on with same topic using resources. So there's something called life cycle assessments, LCAS, and this is very similar to carbon footprints, but it's basically for products and it's a way to measure the sustainability and environmental impact a product or like a a hat, let's say, has on its lifespan. So there's a fair few things you need to consider here.

[00:21:53]Well, four things actually. Number one, getting the raw materials. Let's consider a car. Okay. So, if we have a car, number one is getting the raw materials. So, is it damaging [clears throat] to get the materials for a car? Probably. Yeah. They're made of plastic and aluminium. You need to mine the aluminium. Mining's bad for the environment. What materials are needed?

[00:22:09]Let's say aluminium. Does it require energy? Yes, it does. So, that's not great. Next, then manufacturing and packaging. You need to consider does it cause pollution to create and package the product? Well, you need energy to make a car. So, yes. And you need boats to transport it from China and other countries to the other countries. So yes, it's bad as well. Using the product, will the product be bad for the environment when it's used? Yes, cars burn petrol. How long will it last? 30 odd years, maybe a bit less. I don't know. So then that's also not great. But I suppose it lasts quite long. So that's a good thing I suppose. Disposal. Can we recycle cars? Yes, you actually can. So that's a good thing. And will it be end up in landfill? No. Unlikely. So reusable of cars actually is a good thing. But overall, not a very good LCA for a car. Okay. What is recycling then?

[00:22:50]So in your okay so in your exam you need to be able to apply the LCA of everything to the question recycling what is it basically it's a way we can you know recycle you can use something again re means like to do again and cycle you're doing it over and over it's a cycle basically recycling is way way way cheaper than making stuff again like for glass you can just use the same bottle or just clean it so it's way cheaper than to actually just melt down sand and all of that and make glass again. Um and same for metal as well. You can reshape it rather than mining it from the earth.

[00:23:20]So recycling is good just economically and also it's good because we have limited resources. Okay. Two a few more things we need to cover. Extraction of metals. There's something called biolleaching. And biolleaching is when bacteria can convert copper ore. So basically copper in the ground to soluble pure and usable copper. And basically we extract this copper by using the reactivity series. So we b all you need to know is like this process here. We have bacteria and then we extract the copper using the reactivity series. Finally, there's something called phyto mining. And if you have an area full of copper in the soil, plants take up ions in the soil, remember, and it's going to take up the copper. You then burn the plants once it's done, and you extract the copper from the dry leaves. Finally, once again, I've mentioned this here about drinkable and distilled and portable water. When we want to purify water, we need to do a few things. First of all, we need to filter out large objects. Then, we filter out the smaller objects. And then, we sterilize it to kill bacteria. Water is often sterilized with chlorine. Can be done with other things as well. Usually a small amount of chlorine, but nowhere near as much as things like swimming pools. But we need to talk about it. It's a bit more complex. So first we need to screen for the larger objects. And then basically there's a process called sedimentation.

[00:24:28]The sediment is to form like a fine precipitate or pulp at the bottom. So this is when a sediment of fine things form at the bottom. You then remove the liquid. So the water you're going to start using and then you do undergo this into something called aerobic digestion.

[00:24:43]Basically bacteria break down organic matter that is dissolved in the liquid.

[00:24:47]Obviously you don't want that dissolved organic matter because it can be dangerous for you. So bacteria break it down so it can be removed. So there and then you've removed the dissolved things. The solid things or the undissolved things you can see like the sludge and the gunk is going to be removed by anorobic bacteria. This is makes methane which can be used as energy. Remember and also made is other products that can be used as fertilizers in fields which is good for crop economy. Wow. we and that is everything in chemistry paper 2. Remember I didn't go over everything today. I went over the things that were high yield and this is just to see if your knowledge is up to date and check on your knowledge. If at any point you think oh I don't remember that go look it up on other resources such as other YouTube videos or even your own textbook your own notes and make sure to do past questions on areas you're struggling on. As always if you have found this useful and you want to see more content like this it really helps if you drop a subscribe like so we can push it out for the algorithm. If you have a friend who's struggling on GCSE chemistry and needs to see this video, send it to them as well. And as always, thank you for watching.