All of GCSE Chemistry Paper 1 in UNDER 25 minutes (taught by a med student)

Added: 2026-05-07

[00:00:00]We're doing chemistry paper one today.

[00:00:01]We're covering the entire GCSE chemistry paper one, and this is what I did when I got my grade nine in chemistry many years back, and this video is more for those who want a final whistle-stop tour and want to see if they actually know everything and then continue to learn from there. This doesn't go over absolutely everything, and it does skip some parts. They're going to I'm going to decent detail in some areas, but in some areas I don't as well. I try and teach you in a way which you will understand. Let's get going.

[00:00:29]So, the first topic is physical chemistry. In physical chemistry, it's all about what is inside atoms, okay?

[00:00:34]So, we have the periodic table, and within these atoms and these elements, we're going to have the nucleus, okay?

[00:00:39]In the nucleus, we're going to have protons and neutrons. Protons, think positive. They weigh one, and they have a charge of one. Neutrons are neutral.

[00:00:46]They weigh one, but they have a charge of zero, and electrons, think negative.

[00:00:50]These are negative one, and they have a charge of zero. Here then, we need to look at the periodic table. The periodic table is basically what everything is made of. We have two numbers we need to be aware of. The top one is the mass number, and the bottom one is the atomic number. The mass number, okay, is going to be the number of protons.

[00:01:07]Okay? So, think six is going to be six protons. Whereas, the atomic number is the number of atoms.

[00:01:14]So, it's going to be the number of protons and neutrons. You need to know that. Okay, there's a few things we need to go over. Isotopes is basically when you have the same number of protons, different number of neutrons, okay? Same protons, different neutrons. Protons never change in the periodic table.

[00:01:30]Let's count, okay? Let's go to the sixth element. 1 2 3 4 5 6. Carbon's the sixth element. How many protons will it have?

[00:01:36]Six, okay? So, it always goes like that.

[00:01:39]The top number here is the one where the number of protons are found. Okay, and always protons equals electrons unless you have something called an ion, which is basically different number of electrons. That's all you need to know.

[00:01:51]Okay.

[00:01:52]The mass number as well down here, the atomic number, sorry, is going to be protons plus neutrons, and protons is always the number up here. You need to know that. It comes up often. Two definitions. Compounds are elements joined together in different proportions. Think H2O, like that. And then, mixtures is when they're not chemically joined together. So, like sand and water is a mixture. It's not chemically joined together, okay? Then, you need to know this definition here.

[00:02:14]Relative atomic mass equals the sum of all of the isotopes times the abundance over 100. There's an example here. Work it out in your own time. Okay, next then, we need to go over types of ways to purify things. There's these four methods here. I recommend you learn them all in your own time, and they all have different functions and negatives and when you would use them for. You need to know when you would use each of these individually.

[00:02:36]Next then, we need to know about the evolution of the atomic model. So, we start off with something called the plum pudding model. If you have ever had Christmas pudding, it's literally like a plum pudding. So, basically, it says there's negative electrons dispersed like raisins in a plum pudding, and that's the model. There's limitations because we actually now know electrons orbit in shells, but this is a definition of it. It's basically solid spheres of positive charge with negative electrons floating like uh raisins in a pudding. That's all you really need to know. We then actually moved on to the nuclear model, which is basically when we have positive charge is concentrated in the center, and we started to think of this idea of a nucleus. Remember, in the nucleus, there's protons and neutrons, and protons are positive. So, we have this positive charge. Then, we adapted this even more to the Bohr model. So, a guy called Bohr made this, and he basically said, we have this nucleus where all the positive charges are, and we have these electrons orbiting in different energy levels. And you you would have heard of the 2 8 8 16 rule. That's where the electron shells come from, okay? Right, that's all of that part done. Next then, we need to know about some of the periodic table. So, periodic table is in groups and periods. Groups go down. So, group one, group two, group three, group four, all of that. Then, periods go across. Here's what's really important.

[00:03:47]Elements in the same group have the same number of electrons on their outer shell. So, if I say group one, they're going to have one electron on the outer shell. Group two will have two electrons on the outer shell. This is super important because the number of electrons on the outer shell overall determines elements' reactivity, okay? So, elements in group one are going to react really similar. Elements in group two are going to react really similar cuz they have similar amount of electrons on the outer shell. Periods is when you go across the periodic table, and this period basically means how many shells of electrons do they have? So, period one, hydrogen and helium, they're going to have one shell of electrons. Period two, lithium, beryllium, boron, carbon, nitrogen, oxygen, fluorine, and neon, going to have two shells of electrons cuz remember, 2 8 8, do you remember that whole rule? That's why it's important. That's periods and that is groups. Okay, we need to know group one.

[00:04:38]Group one are known as the alkali earth metals. Just really quickly, the metals in periodic table is basically this stuff here, and then this stuff here are the nonmetals {slash} gases generally, okay? So, alkali metals, they have low density, they're soft, they can be cut, we say they are malleable, and they're really soft. We store them in oil so not to be oxidized.

[00:04:58]Uh they all react very similarly. Why?

[00:05:00]Cuz they only have one electron on the outer shell. Incredibly reactive with water, and they get more reactive with water as you go down the group. Here are some examples, potassium, sodium, lithium. They form ions. They form ions to form their 1+ ions. So, it goes K+ Na+ Li+. The reason for this is because we want to In chemistry, generally, you want a full or empty outer shell. So, let's take sodium, for example. It's in group one, so let's pretend this is outer shell. It has one electron on the outer shell.

[00:05:28]It reacts to lose electrons so it becomes more stable, zero electrons on the outer shell. Electrons are negative.

[00:05:35]If we lose something negative, it becomes positive. That's a sodium ion.

[00:05:38]It's more stable. That's why these form ions, and their reactivity increases down the group. Great. Next then, we need to know group seven. Group seven is this here. These are known as the halogens, okay? So, if it's in group seven, how many electrons does it have in its outer shell? Seven. Okay, halogens are quite reactive. They all form colored vapors. They're nonmetals because remember, I said these areas are nonmetals.

[00:06:00]>> [snorts] >> Uh they form ionic salts, and they are diatomic. Diatomic basically means there are two of them when you find them normally in nature. So, chlorine doesn't exist like that. It exists like Cl2. Why is this? Remember how I said, you want a full outer shell or a negative outer shell in chemistry. If chlorine's in group seven, let's draw its outer shell of electrons. How many electrons will it have in its outer shell? It's in group seven, so it's going to have seven. This isn't a stable, whereas if we have something called a um covalent bond, more on that later, and we do this, and we share some electrons. Let's do one here and one here. 2 3 4 5 6 7. We have now a full outer shell. Chlorine's happy. These are diatomic. So, Cl2, F2, I2, Br2. Worth knowing that. Okay, they These form salts with the group one metals. These can gain electrons. These ones lose electrons. Okay, carrying on from that then is group eight. Group eight is the final group. These have eight electrons on their outer shell.

[00:06:54]Remember the rule, 2 8 8. Their outer shell therefore is full. Therefore, these are stable, very stable. These are unreactive. These are known as the noble gases, okay? That's what you need to know. And then, finally, on the physical chemistry topic. This one's a long one, but the other ones are really short, okay? In the physical chemistry topic, this is like changing in um particles.

[00:07:12]So, solids are going to be really really really compact, and there's not many ways to rearrange a solid. This Vaseline here, I can't rearrange it because it's going to be one shape.

[00:07:20]However, some liquid then, when you melt something, liquid can take many shapes.

[00:07:24]You can pour it into a cup, it can take the shape of a cup. You can pour it into like a coffee mug, it can take the shape of a coffee mug. And then, when you evaporate it, which is boiling, gases can take any kind of form really. They can go anywhere. And then, the reverse applies here. So, condensation is gas to a liquid, and freezing is liquid to a solid. Know each of these. Know the diagrams, really worth knowing. Okay, bonding now. We're on with bonding. So, there's three types of bonding, covalent, metallic, and ionic. We need to know each of them. Covalent is the sharing of pairs of electrons. Covalent bonding is probably the most common kind of bonding I would say, and let's talk about chlorine, okay? So, chlorine, remember, group seven. It has seven electrons on its outer shell. Let's draw these in dots. So, 1 2 3 4 5 6. Let's do one here, seven, okay? Let's get another chlorine molecule, and we're going to overlap these shells of electrons. So, let's draw 1 2 3 4 5 6 7. If we count each of these chlorines uh the electrons individually, we have 1 2 3 4 5 6 7 8, and then we have 1 2 3 4 5 6 7 8. So, we have enough electrons on the outer shell. This means they have a full outer shell. Remember, full outer shell {slash} empty outer shell equals stable.

[00:08:37]Okay? Covalent bonds are very strong, very strong. So, you see some structures like diamond have covalent bonds, really really strong, and you need to know its applications for that. Next is metallic bonding. Metallic bonding talks about the metals. So, if we go back to here, metals are going to be these Well, these are transition metals, but then also some of the other metals as well, depending on if they're bonded or not.

[00:08:58]But, the transition metals generally are just general metals, okay? So, all of these as well. So, with the metals then, they basically form ions. So, remember, ions is same number of protons, same number of neutrons, different number of electrons. Let's take aluminum, for example. Aluminum forms a Al3+ ion. This means it's lost three electrons. So, we're going to have three electrons per aluminum ion. Aluminum metallic structure looks like this, and we have all of these Al3+ at ions with this We say a sea of delocalized electrons.

[00:09:34]And this sea of delocalized electrons is what allows a current to be conducted.

[00:09:37]This is the reason why metallic uh metallic structures can conduct electricity. Also, the electrostatic forces of attraction between the positive ions and negative electrons is what causes their temperature melting point to be so high. All metals in the periodic table are solid at room temperature, meaning they have a very high melting point, apart from mercury.

[00:09:57]You don't need to know that, but you do need to know they have a high melting point. That's one of their properties.

[00:10:01]Finally then, we have ionic bonding.

[00:10:02]Ionic bonding is between a metal and nonmetal, and it's the exchange of a pair of electrons.

[00:10:07]Sodium chloride, that is what common table salt is chemically, okay? So, sodium is group one. Remember, let me go to a period table. Do we want to We want to make this either a full outer shell or an empty outer shell? If it's group one, sodium, sodium's here in group one, do we Do we want to make it a full outer shell or a negative outer empty outer shell? What's easier? Empty outer shell.

[00:10:29]So, it goes Na. It has one electron in the outer shell.

[00:10:32]Chlorine, over here, group seven, has seven electrons in its outer shell. How do we What's better? To make it a full outer shell or a negative empty outer shell? It's going to be a full outer shell. So, what if we give this one here to him? So, then we go Cl with eight electrons in the outer shell, sodium with zero electrons in the outer shell.

[00:10:48]Everyone's happy. Remember, 2 8 8.

[00:10:50]Everyone is happy now. So, this forms sodium chloride, salt. That's ionic bonding, the share the exchange of a pair of a a single electron, okay? So, we have sodium plus Cl minus. We don't show the pluses and the minuses, they cancel out. So, we just say NaCl. But, they've swapped electrons. Cl is now negative, it's gained an electron.

[00:11:08]Electrons are negative, so if you gain something negative, you get even more negative. Sodium's lost an electron, so it's now more positive. Okay, that's all to do with that. There's a table here comparing all of them. You need to know this. Read up as well on giant covalent a giant covalent as well. It's really important you know about that. But, these is kind of the general description and summary of that. Screenshot it, learn it. Okay, next is polymers.

[00:11:31]Polymers are basically big molecules made up of many repeat units. So, a monomer, for example. So, we could have like, let's say, ethene, C H C C H H H H. That's ethene, but then if I have polyethene, it'll be like this.

[00:11:51]Many, many, many ethenes joined together, and you remove the carbon double bond, but don't worry about that.

[00:11:56]But, basically, you have many, many of these together. You put n. N means basically means like many, many more.

[00:12:00]It's a repeat unit, okay? That's what polymers are, you need to know that.

[00:12:03]Okay, that is all of that done for bonding. Okay, next is quantitative chemistry. Right, really, really, really important. There's a thing here, relative formula mass is basically the sum of the atomic masses. Let's take CO2, for example.

[00:12:15]The relative formula mass of CO2 is the sum of the atomic masses. Let's go back to the periodic table. What is the atomic mass? The atomic mass is the one at the bottom. Basically, the number of atoms. So, for example, it's not shown in this one here, but the carbon I drew up here, for example, will show you it's 12. That's the atomic mass, okay? Number of protons and neutrons. You need to know that for relative formula mass.

[00:12:35]It's super duper important. So, if we go back here then, we have here, yes.

[00:12:42]Relative formula mass is the sum of the atomic masses. So, here we have CO2, it's going to be 12 plus 16 lots of two, 44. The relative atomic mass therefore of CO2 is 44. It's really important we know that. There's an idea to do with conservation of mass. Conservation of mass is the idea that energy cannot be created or destroyed, only transferred from one system to another. Basically, you can't make or destroy mass, you can only just convert it from systems. It's really important in chemistry, because let's say we do combustion of CH4, so we're combusting it. O2, it's going to make CO2 plus H2O. I'm happy that this is balanced, so I'll put a two here, okay? A two there, I'll put a two here.

[00:13:17]The thing with this is, you can't create or destroy atoms. You must balance it on both sides, okay? It's really, really, really important we know that. So, the relative formula mass on the reactants is going to be the same as the relative formula mass of the products. We can't create or destroy atoms or energy, for that matter, okay? Right, next then.

[00:13:33]Moles is a definition. This is basically the amount of stuff. Like, sometimes people say it's molecules, but don't worry too much about it. Moles is the amount of things. One mole of anything in chemistry is 6.02 * 10^23 particles.

[00:13:46]Basically, it's an insanely big number.

[00:13:48]Particles are tiny, moles are big. Okay, you need to know this. This is the most important thing to take. Moles equals mass over Mr. A good way to remember this is moles equals grams over rams, relative atomic masses. Grams over rams. I used to do that, okay? Make sure you know how to rearrange an equation. So, sometimes people like it as a pyramid. So, if this was a pyramid, it would look like this here, mass over Mr. This would be the pyramid, and you can rearrange it by just putting your hand on the area you want to do, and then covering it out and making that the subject. Okay, here's the equation for moles equals mass over Mr. Make sure you know it, and do that one there. Next one is triple only. These are for both for triple. It's basically percentage yield equals actual over theoretical times 100. And atom economy is Mr. of desired Mr. of all times 100. You need to know them if you're triple only. Next then is this here, okay? I've talked about Avogadro's constant. So, we said Avogadro's constant is basically this idea that it is 6.02 * 10^23 particles per mole. So, if you want to work out the number of particles, literally do moles times Avogadro's constant. So, for example, if we have one mole of sulfur, and we want to find out how many particles are in it, you do 1 * 6.02 * by 10^23, which is going to be 1.

[00:14:57]6.02 * by 10^23 particles of sulfur in one mole. Remember, moles is just amount of sulfur. That's all you need to know. There are some equations here and some written examples. Make sure you go over these in your own time.

[00:15:13]Okay.

[00:15:14]This is a a written equation as well to do with percentage of mass by compound.

[00:15:19]You need to know this. Go over it in your own time. It's explained all here.

[00:15:21]All the notes are on CameraVise. As well, here we have balancing equations and calculating the mass. Something really important for this one is concentration equals mass over volume.

[00:15:31]When we go over this here, concentration, what is concentration given in? Concentration is in grams per unit of volume. So, like, it'll be grams per liter, for example. So, therefore, we know it's going to be mass over volume. You need to know that equation there, okay? Next then is going to be excellent limiting reagents. This is a very, very, very difficult topic. So, if if you don't really understand it, I honestly would recommend just leaving it for now, because it's going to be really hard to learn in such a short amount of time. There's a written example here, and I would recommend going on CameraVise. The notes are all there for you. I need to talk as well really quickly about balancing equations. So, let's let's take a combustion equation.

[00:16:06]So, let's do C3H8 plus O2. Okay, so combustion is going to make CO2 plus H2O. When When balancing equations, you need to split it into two, and you need to do carbons, hydrogens, and oxygens, okay? Always, always, always, I would recommend doing the carbons first. So, do carbons first.

[00:16:24]Here, we have three on this side.

[00:16:26]Carbons, hydrogens, oxygens, we have one on this side. Put a three here. Great.

[00:16:31]Now we have three on this side. Next, do oxygens. How many Sorry, hydrogens. How many hydrogens do we have on the left-hand side? Eight. How many do we have on the right-hand side? We only have two. So, we need to put a four here, okay? Now we have eight. How many oxygens do we have on the right-hand side? Well, we have three lots of two, so six plus four, 10. How many do we have on the left-hand side? Two. So, we need to put a five here. This is ratios, okay? So, now we've balanced it here.

[00:16:53]You need to be able to get good and slick at balancing equations. Loads of stuff on CameraVise if you want to go over that. Next is chemical changes.

[00:16:59]Chemical Okay, gosh. This is the reactivity series. You need to know the reactivity series well.

[00:17:05]And basically, this is a nice like What's the word? Pneumonic of remembering it. And the reactivity series is important for many reasons here, and I'm going to label here carbon as well, cuz I need to go over that later. So, we have these things here called displacement reactions.

[00:17:17]Displacement reaction is when you displace something. So, we have copper sulfate and magnesium. Copper sulfate is CuSO4 plus magnesium is going to be Mg. So, where is magnesium? It's here. Where's copper? It's here. Magnesium's more reactive. It's going to displace it, okay? So, we're going to have MgSO4 add Cu. That's the displacement done.

[00:17:41]Simple, right? Next then, you need to know this idea here. If something is less reactive than carbon, which is why I labeled carbon off here, it can actually be extracted via reduction, okay?

[00:17:53]From their oxides. And this is really important for like chemical industry and getting some metals that we need. Let's say just iron, okay? So, iron is below carbon. Iron can be extracted from iron oxide via reduction using carbon. Okay.

[00:18:08]There's something called redox. You would have heard oxidation is loss, reduction is gain. Oil rig. What does that even mean? Okay.

[00:18:16]When we oxidize something, we lose electrons. When we reduce something, we gain electrons. I'm going to explain this in detail. So, let's take zinc and copper sulfate. So, zinc is Let's take zinc and copper sulfate. Zinc is really high in the reactivity series.

[00:18:31]It's here, it's above copper. It's going to displace it. So, first of all, we're going to have Zn plus CuSO4 is going to make ZnSO4 add Cu. So, what has happened here? So, we've gone from zinc on its own, okay?

[00:18:48]So, Zn then it goes to Zn2+ cuz it forms this thing here with sulfur. And sulfur is a two negative ion, this zinc's going to be a two positive ion here then. So, zinc actually has been oxidized.

[00:19:12]Because it has lost electrons, okay?

[00:19:14]It's lost these two electrons here to join with sulfur ions. So, it's going to be plus two e minus. On the other way round, CuSO4 is actually made up of copper ions and sulfate ions, okay? So, copper is going to go from Cu2+ is going to gain two electrons to make Cu. Look, Cu on its own. So, it's going to be reduction.

[00:19:36]Okay, it's gaining electrons. You need to be familiar with redox. They're really important. Next up is acids and bases, okay? So, acids are basically when a pH is less than seven. Bases is when the pH is more than seven.

[00:19:48]Something neutral, like water, is when the pH is seven. Strong acids dissociate well into their protons and weak acids don't dissociate very well. So, a strong acid would be HCl. This basically in solution will dissociate into H+ ions and Cl- ions. pH is determined by the concentration of protons here. That's what pH is determined by. It stands for proportion of hydrogen, I think. So, pH is to do with how many H+ ions there are. Loads of H+ really low pH, okay?

[00:20:17]Right, you need to know something about electrolysis. Electrolysis basically is how we can split up metals and things of anything really, ionic solutions within molten solutions. So, we have an anode and a cathode. Anodes are positive, sorry. Positive is anode, negative is cathode. So, if you have sodium chloride, sodium makes positive ions, chlorine makes negative ions.

[00:20:40]Chloride ions go to the anode, sodium ions go to the cathode. You need to read up on this in more time. I don't have enough time to talk about this today. I really recommend watching videos on this, though, and understand how each of these work. Okay, next up then will be energy changes and we're almost done.

[00:20:54]So, energy changes If anyone's played Rainbow Six Siege, think exothermic.

[00:20:58]Think of these exothermic charge.

[00:20:59]Basically, heat energy is given off.

[00:21:02]That's what exothermic is. So, it goes from the reactants to the surroundings.

[00:21:06]So, like fire, burning fire is exothermic. Endothermic, you take energy in. So, then cold things will be cold your hands when you snap them and they go really cold. It's taking heat energy from the surroundings, go into the reactants and it's making it really cold. You need to know this reaction here and this practical to do with the polystyrene cup. Notes on Camera Vise, give that a read up. Okay, and then there's something called activation energy. Activation energy is the minimum amount of energy required for a reaction to take place, okay? You need to know that. So, we have these energy profiles here. When it looks like this, this is basically a exothermic reaction. Why?

[00:21:39]Because energy of the reactants is less more than energy of the product. So, where is the energy gone? To the surroundings. It's released heat energy.

[00:21:48]You need to know a few things here. This increase in energy is known as the energy activation or activation energy.

[00:21:53]That is this here, this gap, is the minimum amount of energy required for this reaction to take place. And then this gap here is the amount of energy released into the surroundings in the exothermic reaction. If it was an endothermic reaction, it would look like this. And then this here is the activation energy and this here is the energy change or energy taken in and heat energy is taken in in exo-endothermic reactions. And finally, you need Oh, please, please, please learn this. Okay, energy changes is sum of bonds broken minus sum of bonds made. Basically, go over this one here and watch a video on this if you need to. I can't stress this enough.

[00:22:30]It's really high yield, this. And that is everything. We've covered all of the four topics thus far. And this is kind of, like I said, a really quick whistle-stop tour. I didn't cover everything. So, there's some areas that I didn't go over because it's not as high yield and also you need to do it in your own time. Use this. If you don't know some areas and you think, "Oh, I can't balance equations really well. I don't know redox really well. I don't know how to do polymers really well."

[00:22:52]Then go over it from there. Don't use this as your main source of studying because it doesn't go over everything.

[00:22:58]And that is everything. Thank you so much for watching. Sorry for not being around recently. I've had my final exams and they're all done now and they went really well. Send this to someone or one of your friends if they need to be studying chemistry. We're going to have a paper two video out very soon. Best of luck in your GCSEs. I know they're just around the corner. Keep on working hard.

[00:23:13]You are doing absolutely amazing, guys.

[00:23:15]And as always, thank you for watching.