Y10 Triple PPE 2025 Q1 (from paper 1 2020)

[00:00:02]I'm going to walk you through the mock paper you did this year 2024 uh mock we use as you can see probably underneath the tipex here the paper that was published in 2020 was a pandemic year so it wasn't sat in in May by people but was used in um autumn for people that weren't happy with their grades. This was a paper that was used. Um I took out 45 minutes of questions and I also added um some a question from paper two as you'll see towards the end. So I didn't use all the questions but it's a good idea of the kind of things you'll get in a GCC chemistry paper right it was the paper was tough I thought it was quite difficult and that's that's a be challenge this stage right so there's a lot in the first question about structure and bonding this is one of the most important topics I would really encourage you to spend time getting your head around it studying and and learning we got to get their head around what we mean by intermolecular forces this comes up a couple of times in this first topic so intermolecular forces is a force of attraction ction that happens in between molecules in between molecules. Now molecules refers to substances that are bound using simple uh simple coalent. So an example would be one of these on here standard example might be something like water. So that's a water molecule made of two hydrogen's and one oxygen joined together with coalent bonds. So there's a bond between the hydrogen oxygen and the other hydrogen. But the reason that water is a liquid at room temperature for example or a solid below zero is there are weak forces between the water molecules which can be overcome if you heat the water up. Um but um they are they are relatively weak much much weaker than coalent bonds. Coalent bonds are the lines we draw between the atoms.

[00:01:52]Okay really important idea. If you're finding this hard and difficult, you must get uh get your head around this, talk about it with your teacher before um before too long. So, water's one of them. Um I thought it was a much harder question to get the other one which was polyethene and I'll talk about that in a second, but you can work through the others and recognize by process of elimination it had to be polyethine. So, diamond is giant coalent, magnesium is a metal, sodium chloride is giant ionic.

[00:02:19]So, it had to be polyethene for that reason alone. But if you think of a polymer as like wet bits of spaghetti or cooked bits of spaghetti in a pot, they're long molecules, long chains of molecules. We studied these in much more detail in the back end of year two, year 11. There are weak forces between those long polymer chains and that's what's going on there. So I'm not too worried if you didn't get that for now. We'll do a lot more on polymers next year. Then what you have to do for for the main bit of this question was discuss the bonding and structure of three compounds. Okay?

[00:02:51]So there's lots and lots of things you could have said um here to get the marks exactly how the marks were issued by the examiners is very difficult to predict.

[00:02:59]So we've done our best to be consistent with marking but I wouldn't overly worry about your score or what you got compared to a friend let's say but I'd be more concerned about thinking about what you should and shouldn't know about this this idea because these are very very common questions. Okay so let's do them one at a time. So carbon dioxide the picture of it was given to you in your in your paper. It looks something like that. These lines are representing um strong covealent bonds.

[00:03:29]We know it's coalent cuz this is a non-metal and this is a non-metal. So there are strong coalent bonds between the atoms between. So people using vague terms like molecules or ions or whatever but these are atoms that have been joined together. You might have said in your answer what a coalent bond is or you should have done. So it's a shared pair of electrons and you should have said really these are double bonds as well. So there's two um shared pairs of electrons between the oxygen the carbon and that carbon and the oxygen there as well. So um mentioning their nonmetals was worth uh noting. uh they're both non-metal atoms which is what the clue that it was um simple coalent and these are what we call molecules. Okay, so there we are.

[00:04:20]So therefore they'd have intermolecular forces between them and people again were pretty unclear about unclear about this. The intermolecular forces were between the molecules in between one carbon dioxide and another. So, just like I did in the previous page, CO2, CO2, CO2. When CO2 turns from a solid into a gas, as it does if you heat it up um you know, dry ice, which is which is what this stuff is when it's very cold, you heat it up, the weak, very weak forces between the carbon dioxide molecules break. Okay.

[00:04:55]So, that's um carbon dioxide. You've got magnesium oxide. The structure of that is given in the picture. It looks like this. This is a latis of oppositeely charged ions. And really, you should have got that. It was given to you in the question. The ions are labeled with charges. The atoms are not labeled with charges. So these are um ions and we could give you some credit for that but really it was given to you in the question. So not too much. You should have been clear that was a giant structure because it goes on infinitely in in three dimensions and it's a latis described as a latis structure which is this arrangement of oppositeely charged ions. plus minus plus minus plus minus plus minus over and over again in three dimensions for gazillions of of ions.

[00:05:42]Okay, should be clear. The magnesium is 2 plus oxide 1 minus which was given to you in the question. I'm going to ionic because we've got a metal and nonmetal metal and non-metal.

[00:05:54]And my classes have seen this, but it's a nice way to show people that metals make positive ions. If you can't work it out when you're under the stress of an exam, metals got a plus in the middle of the word. If you write it like that, a nonmetal's got a minus in the middle of the word. So, if you've got a metal and nonmetal, you'll find you get a plus and a minus. Really easy to work out which one's which. So, you get credit for saying it's a giant structure. It's a lattice structure. Um, and you get credit for saying that the ionic bonds are strong. Again, some of you went on to explain then that that meant it had high melting point. Uh, but you didn't need to do that. wasn't worth any any marks, but you were expected to talk about how ionic bonds formed, which is whether there's a transfer of electrons. Ideally, you should say two electrons from magnesium atom to an oxygen atom to make a magnesium ion and an oxide ion. You should be talking about that. Um, and lastly, silicon dioxide. Again, it should be clear from the picture that these are atoms because there's no charges on them. And it should be clear that this is a giant structure. Again, you've got this very um sort of um large three-dimensional structure goes on in in every direction for or three dimensions if you like for a long way.

[00:07:17]So, SiO2 3D um giant structure.

[00:07:24]It's very similar the structure to to diamond. And if you if you know the structure of diamond and look at how the silicon atoms are placed, they're set up in exactly the same way as in as in diamond, you should have identified the fact that they're it's coalent bonding again cuz it's nonmetals.

[00:07:41]You've already said what a coalent bond is up there. Coalent bonds, non-metals only.

[00:07:49]You could have talked about the fact that coalent bonds are very strong again. And you might have talked about then the properties which you didn't have to do. You you were told as examiners to ignore that but you should have identified that they're single bonds this time though which you can see from the picture.

[00:08:06]But the key things the most important things I would say it's giant structure giant structure and this is a did I even say it simple coalent simple coalent structure up here. um probably the most important things to get across and that leads then to the different properties we know about.

[00:08:28]Okay, I'm going to do one more question.