AQA Physics Paper 1 Last Minute Revision Livestream

Added: 2026-06-03

[00:00:49]All right, I think we're working now.

[00:00:58]Do you think we're working?

[00:01:04]Yeah, things are much better at my end though.

[00:01:13]Had a lovely computer crash, so that was fun.

[00:01:33]So, I'll give it a little bit.

[00:01:36]We'll see how this goes because obviously it is annoying that that happened.

[00:01:42]Such an such a rookie setup. That's what it is.

[00:01:46]Causing a crash.

[00:01:50]Oh. Oh, stop knocking that as well.

[00:01:53]Amateur hour.

[00:01:59]Okay. Right. I knew I knew we had electricity last time, but at least uh I I'm testing everything works now after the crash. So, that's beautiful.

[00:02:12]Right.

[00:02:16]Okay. Electricity.

[00:02:18]Okay. Uh is there any particular thing in electricity or just all of it? Uh I mean all of it might be a little bit tricky but if there is anything in particular obviously um I can start with that.

[00:02:48]Okay.

[00:02:53]Right. So, electricity kind of has a few kind of aspects to it really that you need to be happy with.

[00:03:02]The first one is circuits.

[00:03:05]Okay. Actually, what they are. Okay. Uh that includes things like your kind of uh like basic units, what they mean, how they relate to actual electricity. Um you've got required practicals.

[00:03:24]Um now uh mostly uh you've got the resistance in the wire that's the bigger uh you've uh got like electricity like so domestic electricity like electricity in the home.

[00:03:47]Okay. Um and and obviously as always in this paper there's a hearty amount of equations. Um so the first thing I suppose to think is what actually is electricity because we often kind of overlook that. So electricity electricity is uh it's quite simple really. Okay, it is uh a charge uh now most often that's negative charge because of the electrons.

[00:04:29]Okay, moving in a circuit.

[00:04:35]Okay, so fundamentally for an electrical circuit um you need to have uh some form of charge and a closed loop. If you don't have closed loop, you're not going to have electrical circuit. Uh unit conversions. Is there any unit conversions in particular that you find tricky or is it just like the milliamps and all of like kilows and stuff like that?

[00:04:58]Um okay.

[00:05:02]Now there are kind of three to four main units with uh electricity. First one we need to be happy with is current. And current is our flow of charge.

[00:05:18]And all of these were discovered by old 1700s white men. So they named them after themselves obviously. Um so current is our flow of charge that was named by uh Mr. Ampair. So that is the amp. Okay. Um you then have uh potential difference. No potential difference is quite a weird one because um multiply divide. Okay. Yeah, we're going to do we'll do some equation practice because I think like if you can smash an equation question on this, you're going to get like half marks.

[00:05:53]Um so, uh you have potential difference.

[00:05:59]Now, that's also called the voltage, and your teacher will often call it that, which gives away what it is. Now, I like to think about this as kind of it's the energy per charge, but in normal words, what do I think of that as? I think of that as kind of the push, how much oomph it's got as it goes around the circuit. Uh, and this is measured in volts.

[00:06:23]Okay? Uh, you have uh resistance.

[00:06:28]Resistance is how much you oppose the flow. So, that's kind of the opposition to the current.

[00:06:38]And again, this was discovered by Mr. Ohm. Okay. Uh that has a funky symbol that looks like that. Okay.

[00:06:47]Um so we've got our basic unit. So this is probably quite a good idea to start to introduce the equations. Now remember, you do not need to remember the equations, but it is a bit weird because uh the unit of this is a for amps, but in equations, it's given the letter I. Okay, this one's easy because it's V and V and resistance and equations is R and then it has that weird symbol for the unit. Okay, so first thing is just make sure you use the equation sheet. Um you'll know that uh in lessons to death I talk about FIFA.

[00:07:30]Okay.

[00:07:32]uh and the reason I talk about FIFA is not the corruption ahead of the World Cup but instead okay because if we follow it we will get as many marks as we possibly can on these equation questions. So we formula we insert we fix and then we get the answer. So when you're talking about if you should multiply or divide that really is this stage the fix. Okay. So, I'll tell you what, I've got a few past papers near me here.

[00:08:06]Um, so here's a simple one. Here's a simple one. Okay, it says here, uh, a student, uh, connects a resistor to a cell for 60 seconds. The current through the resistor is 0.97 amps. Calculate the charge flow. Now, again, it'll either be given to you or is in the equation sheet. So, you've got it there. Now, even though it's there, I'm going to write it again because I want to follow that idea of FIFA. So, Q= T is it in symbols, weirdly. Okay, so that's my formula done. Tick. I'm then going to stick the numbers in. I don't care about units at this point. I'm going to stick numbers in. Okay, so Q is what we're trying to work out. That's the charge. No idea what that is. I is 0.97.

[00:08:56]time is 60.

[00:08:59]Okay. Now, here just so happens that that's in seconds, which is fine, and that's in amps, which is fine. So, we're kind of doubly okay. Everything here works out as a time, so I don't need to do any fixing or anything like that.

[00:09:12]This is as straightforward as it gets.

[00:09:15]Okay. No such thing as an old calculator, science paper. Stick that in. And that would be Oh, off top of my head.

[00:09:27]Um uh it's like 67.2 something like that. Okay.

[00:09:37]And uh uh and then uh C for kudos. Okay.

[00:09:42]So that is our first bit. So that in a normal equation this so far you'd get a mark for sticking it in and you get a mark for the answer. You'll notice this is three marks. So that means there's three things to do. Stick it in answer.

[00:09:56]The third thing is for remembering that two significant figures. So this to two significant figures will Oh, great.

[00:10:05]Um 67. Great. I hate myself a little bit. Okay. And that would be our three marks. Okay.

[00:10:14]Now, let me locate you a harder one where I show you how to think about um it more with the rearrangement.

[00:10:26]Uh let's do what's the energy. So, that's still fine.

[00:10:32]Ah, here we go. Right ear is an absolute classic.

[00:10:40]Lovely.

[00:10:42]Right. So it says here the potential difference across a piece of wire is 2.1 volts. The current in the wire is 0.3 amps. Calculate the resistance of the wire. Write any equation you use. So again we go straight to our equation sheet.

[00:10:57]Bosch, that's what it is. V= I * R. Now that's our F formula.

[00:11:04]So I am still going to stick with what we've said. I'm going to stick my numbers in. Right now this is our voltage. So this is going to replace the letter V. So that's 2.1.

[00:11:17]This is our current. So that's going to replace the letter I. 0.3.

[00:11:22]And then R. We still don't know. That in itself would be one mark. This is why I encourage you to do this. Okay.

[00:11:30]Now this is where you go. You're not sure whe to multiply or divide. This now basically now becomes a maths question.

[00:11:39]All right. So you know you get used to your maths having 6 = 3x find x and you go right well I need to divide both sides by 3 and you would probably even think about it right that okay so this is exactly the same 2.1 = 0.3 * r so let's divide both sides by 0.3 and look I don't even worry about if it's times or divide because I've worked it out just by doing my maths again stick that into a calculator and the answer is 7 ohms and that is going to be there. Okay. So this kind of bit here is where I'm referring to as the fixed stage. Now the other thing that it could do is ask about a unit conversion. Now that unit conversion is a bit more prevalent on the higher tier. Um but obviously it does come up on the foundation.

[00:12:38]Let me locate a nice one for you.

[00:12:43]Uh there's obviously also double equations and stuff on the higher where you have to use two equations.

[00:12:52]Bit Maybe this one's This one's got a beauty.

[00:13:33]Right. Let me um let me adjust this one.

[00:13:36]So, we're going to we're going to get a little bit of a pretend here.

[00:13:40]Okay. So, this one is one about specific heat. I know it's not electricity, but we're talking about equations. Now, here it's already converted. Okay. It says it's 0.072 kg, but let's let's imagine that it didn't say that in the question. It said 7.2 g. Okay, we're still going to follow FIFA. Okay, write the equation. On the equation sheet, you'll find that energy is the mass times the specific latent heat E= ml.

[00:14:11]I look and see which numbers have I got in the question. Well, I've got energy.

[00:14:15]Okay, so I'm going to replace the E with that.

[00:14:20]Okay, M. Well, let's not worry about a conversion yet. Let's just stick our number in. That's 7.2 grams. But in the back of my head, I'm thinking, well, that's not kilograms. I'm going to need to do something there. And then L I don't know. All right, that again would be a mark.

[00:14:37]Okay, so now we enter our fixed stage.

[00:14:41]Now this is a two things to do in this fixed stage. First of all is to sort the units out.

[00:14:46]Okay, now I know I'm covering it up there, but 7.2 g, we've got to put that into kilogram. That means I've got to divide by,000. So that becomes 0. 0.72 * L. Now I've got to remember our kind of algebraic principles. I've got uh 0.02 72 * L divide both sides by that. I'll get L on its own.

[00:15:20]Now you get a mark for the conversion and then you'd get a mark just for seeing that working out. I stick it into a calculator and that's going to get my answer. Okay, that one I'm not going to be able to do. I might be able to do my head.

[00:15:38]Um and that uh I think okay um does that answer your how we work through equation questions kind uh dilemas.

[00:16:19]Okay.

[00:16:21]Um right. Uh is there any aspects of the electricity which um you'd like me to go through? I know I kind of went off straight away on units and then start talk about uh equation questions. Um but is there a particular aspect of electricity that anyone really wants otherwise I will just ramble.

[00:16:44]Um it's not going to be a massive uh one tonight.

[00:16:48]Um but it's at least something and somewhere for you to vent any issues and see what I can do to help.

[00:16:58]Okay.

[00:17:00]Right, I tell you what. Let's do some uh random electricity stuff in here, shall we? And that provides a nice little catalyst for how we're doing stuff.

[00:17:18]Okay, so let's take it back to the basics. And the absolute basics are our circuit symbols. Really good source of a lovely tick box question, right? Which one is a variable resistor? Now um I think that the circuit symbols are quite logical.

[00:17:36]So this is the symbol for a resistor.

[00:17:42]Okay. Now if I put a little dial on it.

[00:17:47]Uh so this is technically a combined science foundation paper but it appears on literally everything. It's unlikely that they'll do a tick box on the higher. It would be draw the symbol.

[00:17:59]Okay, I try and go through fundamentals if I'm honest, which apply to everything.

[00:18:05]Um, so, uh, if I take my resistor and I say, look, do you know what? I want to be able to dial it up or down. That then becomes a variable resistor, right? Can you see how I've just altered the resistor symbol?

[00:18:22]All right. Now, let's say I want the resistor to be affected by light. I circle it, stick some light on it, and that now is our LDR, which is our light dependent resistor.

[00:18:39]And let's say I want to adjust it with temperature. Well, it turns out this line is uh how uh the resistance changes with temperature. Um, weirdly, it's kind of the inverse. It's a little bit odd, but that is our thermister. Okay, so they're all variations of our resistor symbol.

[00:19:02]Okay, because that's fundamentally what they all are. So which one is a variable resistor? I take my resistor symbol, whack a dial on it, that makes it a.

[00:19:09]Which one is a thermister? That's C. So again, in higher it tends to be it'll be a box and say, can you draw that symbol for a thermister? And then you go, yes, lovely. Give me the marks. Thank you.

[00:19:22]um which component will the resistance decrease when the temperature increases?

[00:19:26]Okay, that is C because um this is quite weird when you think about it, right?

[00:19:30]Because what is resistance? Resistance is um uh this is all of them. The tick box questions would be a foundation, but the the symbols appear on actually everything. It's not a higher foundation or anything. Um so resistance resistance is anything opposing the flow okay of the current. So, uh, ordinarily, um, I mean, in class I've always talked about it like I don't know if you've ever seen, uh, the gauntlet in Gladiators, right? So, the gauntlet in Gladiators, they have a big old like kind of um, looks like a halfpipe with the mean old gladiators like stood in there and then they have the person there ready to run through.

[00:20:21]Okay.

[00:20:23]Well, this is like our charge.

[00:20:26]This is like our wire. And these are the ions in the wire.

[00:20:34]Okay. Now, I want you to imagine that I said, "Right, you've got to run through.

[00:20:38]You got to beat these people. How would you do that? How how can you make it easier?" Well, the first thing I could do is I can make this really wide so I've got lots of space to run through.

[00:20:48]Okay. So, if I make it wider, that's easier. Okay. If I instead of having to go through that, I make it really short.

[00:20:59]Okay, that's easier.

[00:21:05]Okay, if I swap the big strong gladiators out for a little tiny year 7.

[00:21:10]Okay, that's easier. So, that is changing the material. So, I want to put a more a more conductive material.

[00:21:21]And the other thing is if I like cool it down, okay, I say, "Right, chill."

[00:21:27]Right? Do some breathing exercises.

[00:21:29]Yeah. Do some mindfulness, right? Whatever. Okay. And then they're all like, "Chill." Okay. If I make it cooler, all of those things end up with a lower resistance.

[00:21:45]Okay. So, if I have a short wire, smaller resistance. If I have a if I have a thick wire, lower resistance. If I make it out of a more conductive material, lower resistance. If I have the wire be cold, lower resistance.

[00:22:01]So, most things if the temperature goes higher, the resistance goes higher.

[00:22:10]The only thing which really doesn't do that, and this is why this is weird.

[00:22:14]Will the resistance in which component will the resistance decrease when the temperature increases? This is kind of opposite and that is why the thermister is its own weird thing. Okay, because the thermister is opposite to what you usually expect. Now, why have I gone off on this tangent?

[00:22:30]That's because this comes up when you are looking at IV characteristics, right?

[00:22:39]So um you have to know certain devices.

[00:22:46]So the first one here right where you have a nice straight line this is the o IV characteristics of an omic resistor something which follows ohm's law is directly proportional.

[00:23:05]Why and how do I know that? because it's a straight line and it's through the origin that makes it directly proportional. Okay.

[00:23:18]The next weird thing you have to uh be familiar with and if I did it backwards it would do like that. Okay. Is this shape. Okay.

[00:23:29]Now this is a filament bulb.

[00:23:35]Okay. Now, how do I remember this to me?

[00:23:42]That kind of looks like a curly F F for filament bulb. Okay. Now, why does it do this curve? Okay. Why does it do this curve? Well, up here, okay, the bulb is getting hotter.

[00:24:03]And if the bulb is getting hotter, we've just said over here, if the temperature increases, the resistance increases. So that means that it kind of flattens out to follow that trend. And the other one that you need to be happy with, okay, is um is this one, okay, where the resistance you basically have nothing nothing, right? And this is a diode.

[00:24:30]Okay? Now diodes only let electricity go through in one direction which is why it's flat in the negative direction. You get this what's called a lag period and then okay so this is a diode that thing. Okay let's look for a Z3 that way right uh going back to this in which component will the resistance decrease when the light intensity increases that is the hallmark of this bad boy the light dependent resistor.

[00:24:57]Okay.

[00:24:59]Again, always feel free to interject with any questions, any queries, any quibbles because you don't need to let my ADHD go wild.

[00:25:09]Right.

[00:25:11]We have got different arrangements of resistors.

[00:25:15]It says two of the arrangements are in series and two are in parallel. Describe the difference between series and parallel. Right. So uh series series circuits are ones where uh the components are in the same loop.

[00:25:39]Okay? And in parallel they are in different loops.

[00:25:52]How can you remember this? Uh in series like if you watch a series on TV they come one after the other. Okay. And also in parallel you get parallel lines.

[00:26:00]Okay. Now what does that mean for our circuit? Well if everything's in the same loop let's think about a river right? If there's no offshoot to the river all the water has to go through every part of the river. So that means that uh the current is the same everywhere in a series circuit. So there's nowhere else for the water to go. But um just like if you've ever been like to the gym or something or you know in PE right and then they say right it's our last exercise um and then they lie to you and you've got one more and you're like I just gave all my effort to that last exercise. You conned me. I've got nothing left. Um like Ian Bill. Okay. um that means that you have to kind of the electricity kind of knows that in a way and uh doesn't give all of its energy to the first thing. So that means that the voltage the potential difference is shared between components.

[00:26:58]Now for a parallel circuit it's back the opposite. Okay. So the current is shared, the flow is shared because I've now got different kind of um uh different paths and the voltage is the same everywhere. Okay.

[00:27:21]So um in at foundation it might be something as simple as components are in one loop in series like this question.

[00:27:28]Components are in one loop in series. Uh they have their own loops in parallel.

[00:27:32]for something higher um a higher tier it might start to be thinking about okay um what's going on with the current what's going on the voltage now um I know that I've got questions coming up with this but let's let's look at this let's see see what's going on here I've got a 10 ohm resistor and then another 10 ohm resistor okay so if I um face Then if I go outside and I face 10 people in my way and then I face another 10 people in my way. Funny enough, in series, okay, the resistance is add.

[00:28:15]So here I'd face 20 ohm total of resistance. Uh at foundation here that is all the calculations to do with it that you will need. Okay, next one. Okay, here I've got five in series five. That means that it would face 10 ohms in total.

[00:28:36]Now, resistors in parallel are bizarre.

[00:28:39]Okay? Because think about it like this, right?

[00:28:46]I've got options now, right? I could go here or I could go here, right? So, imagine I've got a queue of people Right? Because I've now got two paths, I can almost have two going at once. So, it actually means that they get through this much quicker. So, weirdly, when you have resistors in in uh in parallel, the resistance actually decreases.

[00:29:16]That's quite weird. You're adding a resistor, but it actually overall reduces the resistance. Okay. Um it's kind of like turning a single track road into a d into a dual carriageway. You've now got two paths for you to go down that overall actually makes it easier to flow. So uh there is a way of working this out. This would actually be 5 ohms.

[00:29:36]But the whole idea is this would be less than 10 ohms and this would be less than 5 ohms. Okay. So it says which arrangement has a resistance of 10?

[00:29:46]That's going to be R. Okay. Which arrangement has the highest resistance?

[00:29:50]That would be P.

[00:29:52]Okay.

[00:29:54]Right. Uh I'm glad I turned over this because this is another like real gimme section and it doesn't matter what tier it is. This is like we got to think about what can we go into the exam just knowing off our heads. And that is domestic electricity. Okay. There are three wires in the UK plug. God bless it. Okay. Moment of pride for the British plug. Okay. Yeah. You don't need to stick your hand up. Just say it. It's all right. Or you just saying hello. Who knows? You are the Roblox king.

[00:30:29]Maybe you've got what's it? Garden garden grow. Is that the one? Who knows?

[00:30:35]Um, right. You got three here. Okay. Three wires.

[00:30:41]Okay. Um, you've got the live wire and that is brown. P R Brown goes to the right. The neutral wire, the L blue goes to the left. And up above here, the green and yellow. Okay, that is our earth wire.

[00:31:01]Ah, you know what it is. Green and yellow. Green and yellow.

[00:31:06]Okay.

[00:31:08]Um, right. How to remember it?

[00:31:12]Live wire. This is one with all the electricity. If you touch it, your trousers will go brown. Okay. Um, it's quite weird because people think of like Earth as blue, but maybe you think all or like brown because of the dirt, but let's imagine we've got a nice lovely image of the Earth where it's got green on it. Okay? So, our lovely green green earth. Okay. Um, and a neutral neutral blue sky, lovely calm, scenic. Okay. Now, what do they do? So this is at this is what kind of uh uh kind of provides the uh AC uh uh potential difference or alternating potential difference because that doesn't really make sense saying the a the alternating current potential difference is it? Okay. So this this here provides the alternating uh potential difference, right? This is what's giving us the oomph. Now in the UK supply that is at 230 volts. How can you remember that? Because if you touch the wire, it will hurt your teeth. The electrocution will hurt your teeth.

[00:32:29]230.

[00:32:31]230.

[00:32:33]Yeah.

[00:32:35]Um the uh neutral wire provides a return path.

[00:32:45]Okay. So you've gone into the component, you've used it, comes back, right?

[00:32:49]Remember it's alternating. So it's switching back and forwards. But you can think of that about a return path. Now, weirdly this is actually at zero volts.

[00:32:56]Like it should be at zero volts when things are connected in it become 230 volts. If I just looked at it, it would be at zero volts. uh um and that is uh maintained all the way back at at the um at the substation. Okay. At the um step down transformer uh the earth wire should ordinarily not be used. Okay, this is purely there for safety.

[00:33:25]Okay, that's why the British electrical system is good because we mandate that is used unlike freedom land where they do kind of now but they didn't for a while. Okay. Now um that is there only for safety. So it's at zero volts. Okay.

[00:33:43]And it provides a return path should something become electrically dangerous on the on the um on the appliance. Okay. It provides a return path to ground. Okay. um uh in some cases literally a stick in the ground. Okay. Uh uh and that prevents the electricity going to ground via you and your heart. Um so let's look at this question. Uh what is the wire? It is the earth wire.

[00:34:12]What does it do?

[00:34:14]Okay. It can prevent an electric shock from the toaster because it's providing a much nicer path to ground rather than through you and through your heart when it is plugged into the main supply.

[00:34:24]Potential difference between both of those would be 230 volts.

[00:34:30]Okay. 230 main's electricity is an alternating supply. Okay. Now, so that means it's going like that. And this is the other domestic UK supply fact that you need to know which is how quickly it's alternating. What's its frequency and the frequency of the supply is 50 hertz.

[00:34:53]Okay, that means it's going changing direction technically 100 times a second. Okay, it's kind of going forwards back forwards again 50 times a second. Okay. uh like like the okey kokei or something.

[00:35:10]Okay.

[00:35:12]Um the direct supply just that just maintains a constant flow. Okay. Direct supply is kind of like the DC is is I'd say more logical when you think about it with electricity, okay? Because you're just doing it, okay? Um whereas the alternating is change direction. That can seem counterintuitive. Um, but again, if you think about it like if I had a bit of rope in my hands, if you had a bit if you were holding a bit of rope in your hands and I and I shuffled it backwards and forwards, you'd still kind of feel that friction both ways and I'm transferring energy to you. So, what are the main differences here? Well, if I look at this, first of all, we're changing direction. Okay, so we have positive and negative supply. So, we have positive and negative.

[00:36:01]Okay, you'll notice also these bits here, right? Technically, it's at zero.

[00:36:08]So, periods were actually at zero. Okay.

[00:36:12]And the other thing is the peak of the supply is actually higher on this graph than than these ones. Okay? So, you have higher peaks and lower troughs because it all kind of balances out.

[00:36:26]Uh, right. the national grid. Let's use that as an opportunity to revise the national grid. Okay. So, here is our power station.

[00:36:37]Okay.

[00:36:40]In Suffuk, so it's going to be size.

[00:36:42]Well, see, look at it. Beautiful. Okay.

[00:36:45]Love a bit of nuclear. Okay.

[00:36:51]Spend that important time doing that.

[00:36:54]Oh, lovely.

[00:36:56]Beautiful.

[00:37:00]Okay.

[00:37:01]And uh that produces our electricity.

[00:37:03]Now, in an ideal world, I could just go power station to home. Okay. But, uh I'd have to live close to the power station.

[00:37:12]Uh and that's what they used to do. The problem you've got is here you're going to lose electricity. You're going to lose energy.

[00:37:23]And when I say lose, that means waste, right? you're going to waste energy.

[00:37:26]Why? Because it's quite inefficient. So what we do is we do this whole palava.

[00:37:30]That's not what we do. Power station goes to a step up transformer.

[00:37:37]Okay? And what that does is that will increase the voltage.

[00:37:41]But what that does is it decreases the current. And that means that the electricity in that wire, okay, because it's at a high voltage and a low current, that means that it doesn't get as hot.

[00:37:58]Okay? And if it doesn't get as hot, it means you're not wasting as much energy, right? When you charge your phone, right, you it feels hot, doesn't it?

[00:38:10]Right? So, by doing it kind of, you know, in this way, you're kind of you're you're not making it gets hot. You're not wasting that energy. And beauty of this is because I'm not wasting as much energy, I can send this across the whole country, right? I can, you know, I can send this wherever I want.

[00:38:28]There's my lovely pylons.

[00:38:32]Right there they are. Beautiful. Okay.

[00:38:35]And then the problem is this is now say 132,000 volts or 400,000 volts. If I now start to do that into my home, problem.

[00:38:42]Okay, I'm going to start electrocuting myself. It's going to start uh going through insulation. Um, not good. So, to get it back ready for where we are near where you live, you will have a step down transformer. And that puts it down into our our much lower uh thing for our homes and our factories.

[00:39:03]Okay. And obviously this is as we know and we need to remember at 230 volts and at 50 hertz. Okay. Obviously they can then ask you about ways that you're generating that. So uh disadvantages of fossil fuels, advantages of nuclear, disadvantages of nuclear, whatever.

[00:39:22]Okay. They love that for a long answer question.

[00:39:27]Okay.

[00:39:29]Um, I haven't really done the resistance in a wire practical. I I'll be honest, I think that's quite straightforward. Um, uh, does anyone have any particular topics that they are desperate for now?

[00:39:45]Uh, I suppose we've we've we've done a bit of electricity. Um, some people were desperate for particles. I can do some radiation. I can do some energy.

[00:39:55]Whatever floats your boat. Should we do another poll?

[00:39:58]Oh, professional ask a question. Next top question mark particle model of matter.

[00:40:23]Oh, that's actually very interesting.

[00:40:27]Oh, resistance and wire.

[00:40:37]Okay, there is professional professional not scuffed.

[00:40:57]Why is my bottle start to go all kind of whistly all of a sudden?

[00:41:07]Okay, I'll give another 30 seconds and provide a good snack break.

[00:41:16]100%.

[00:41:18]Okay.

[00:41:21]Uh, is there a particular thing in particle model of matter or just I don't like part of matter?

[00:41:31]Oh, 50%. Oh my goodness. Cuz we're overwhelmed with people. Look, who says a vote doesn't matter.

[00:41:46]Oh, look. was in front of me the whole time.

[00:41:50]Right.

[00:42:10]Okay.

[00:42:34]Okay. Uh right.

[00:42:40]So, uh particle model matter. Um right, it has a few bits to it. Okay.

[00:42:48]So, The first one is the kind of basics when you're coming to the particle model, which is what you've probably done all the way since year seven, right? Which is solid, liquid, and gas.

[00:43:07]Okay, remember solid all nice and like that. Uh, okay. Gas all over the place.

[00:43:13]People trying to find that quite easy.

[00:43:15]The hard one is a liquid. Now again the the mark scheme tends to say you have to have over 50% of them touching. So I like to kind of draw it almost like a solid but I'll just kind of give them a jiggle because they can kind of move over one another. Uh the first thing which I would say is properly GCSE with this is the concept of internal energy.

[00:43:38]Okay.

[00:43:40]And you're probably used to saying low energy, medium energy, high energy. But what's actually going on? Internal energy is the sum of two things. It's the sum of kinetic energy, okay?

[00:43:53]Plus the potential energy, okay? And the kinetic energy is the movement energy. Okay?

[00:44:02]And this is intimately related to the temperature. Okay? So this is what gives us the temperature.

[00:44:11]Right? Now here they're only vibrating.

[00:44:13]So it's low kinetic energy. That's what it's called. Here it started to move a little bit more and more kinetic energy.

[00:44:19]Here really wasn't about lots of kinetic energy. Hotter.

[00:44:25]Then we have this thing called potential energy. This is all to do with the state. Okay. Now, it's kind of like I've got two separate bank accounts. I can put money into one. I've put money into the other. Okay. I don't really put both in at the same time. Okay. Um and this leads us to the first kind of main thing I suppose and and that is uh this graph.

[00:44:48]This is called a heating curve or cooling curve. It's going down. Okay.

[00:44:52]Where I've got the temperature and over here I've got the time.

[00:45:00]Okay. Now, as I'm heating this up, okay, you would expect it to just kind of be a straight line, but that's not what happens. Did you get straight line, flat line, straight line, flat line, straight line? Why do you get this?

[00:45:14]Okay, in these sections here, okay, where the temperature is going up, that is the energy going into kinetic.

[00:45:28]Okay, so in all throughout the whole thing, the energy, if I did a graph of internal energy, it's going straight up.

[00:45:34]Okay, but this is not a graph of internal energy. This is a graph of temperature. on these flat bits. Okay, on these flat bits here, here, the energy isn't going into making them move faster. It's going into potential, okay? It's splitting them up.

[00:45:49]It here, we're going from a solid to a liquid. And here you're going from a liquid to a gas. You're putting energy into breaking them apart and doing like that. Okay? It's kind of like um uh in a game where you get experience, right?

[00:46:04]And then eventually you need to like level up because it kind of caps you, right? So here you're putting in experience. Put in experience. Right? I now need to spend time leveling up.

[00:46:14]Right? But I now went a new level. I can put in more experience. Put in more experience. Put in more experience.

[00:46:19]Right? I need to level it up. Right? I can now put in more experience. More experience. More experience. Okay. So throughout the whole thing, you're kind of let you know you're kind of increasing energy, but you have these flat bits. Now, what do they like to ask about you? to say first of all foundation level it might be what is happening at these flat bits change of state if you've got an actual like cooling curve or heating curve they might um say like what is actually happening at each specific one you could also ask you what is the melting point well here is where I'm melting I can look there and that will be my melting point and that will be my boiling point okay so that's another thing that they might ask um now both of these kind of sections have equations related to and they're both in the equation sheet. So the flat bits, okay, where I'm changing state, okay, they uh are all to do with specific latent heat equation, okay, that's E= M * L. And then these bits here where I'm increasing the temperature, these are all to do with specific heat capacity. So the first thing you need to establish if if it's a question like this is what is happening in the temperature. It's going up a specific heat capacity staying the same specific heat. So right uh we'll come back to that. That's that's quite hard.

[00:47:50]We'll we'll do it, but we'll uh do another first.

[00:48:01]Yeah, here we go. So, this one, you can see I've got a change in temperature because it says the temperature of the air in the balloon decreased by 215. If I've got a change in temperature, that's a change in temperature.

[00:48:20]That means we're now looking at specific heat capacity. Okay. Now, I know it gives it away here, but just bear that in mind. How many marks for grade four?

[00:48:30]Um, are you combined or triple?

[00:48:39]Um, so combined, uh, about 50% is always a good sh. Uh the problem is is with the uh equation sheet for physics traditionally now the grade B has been a lot bit higher so you're probably looking at about 45 marks now um you can just like that by the way the grade boundaries are all publicly accessible like you can literally type into Google AQA grade boundaries uh and search through that document and you'll see them uh you do it by paper so I think last year it was maybe 42 something like Yeah, of course it is. I mean, a one-1's a pass. It's just people don't particularly like it. Um, yeah, like depends on what you want to do next year. Um, but 43 not to be sniffed at.

[00:49:32]Okay. Uh, so here and again from our equation sheet, we've got energy equals mass time heat capacity times temperature change. Now, why they decided to use theta? because they're a bit edgy. Okay, it's just T in Greek or it's TH in Greek, but it's like 10 to change. It's like um Mike Tyson doing it.

[00:49:59]Uh yeah, it's all of them.

[00:50:02]That's the thing like people always are like head up on if it's foundation or higher and all this type of stuff. high pretty much everything's in both as if it's if it's something which is specifically on higher you know and I'll tell you it's only in higher um right so again from our equation sheet that's our first thing always write in our formula then we go to insert let's stick our numbers in right well we've got the air and the balloon had a mass of this okay so m is now going to be 0 0320 2 O.

[00:50:39]Okay.

[00:50:41]Now, uh the specific heat capacity I don't know. So, I'm going to put that as C. Okay. The change in thermal energy of the balloon is um uh was 86 uh sorry was 215. So, that's 215. And because I'm a here, it should be 860. Okay. You would get a mark for that.

[00:51:05]Next thing. Whoop. Wobble wobble wobble.

[00:51:08]Next thing we do, okay, is well, let's simplify this side. We now want to treat it like it's an algebra problem. We got 600 860 equals stick in the calculator.

[00:51:20]No such thing as an old calculator science paper. What would that be? That would be that might be a little bit tricky on the end.

[00:51:30]I did do some beautiful mental maths earlier.

[00:51:34]Been a long day, haven't it? Yeah.

[00:51:45]150 688 * C. And again, now, oh yeah, so much maths. I think it's uh it might even be more than 30%. Um, so now I want to get C on its own. So let's divide both sides by this. 860 / 0.688 equals C. If they see that or they see 860 / 0.0 320 * 215, that's a mark.

[00:52:20]That's why we do our fix step because even if you muck up by seeing that, we're going to get our mark.

[00:52:26]Divide that through. Okay. on our calculators and again uh 860 / 0.688 is 1,250 JW per kilogram C. So that is our answer. Uh that's pretty hard.

[00:52:51]Um you'd get close if you smash all the maths.

[00:52:57]you get close, right? Let's do one on hard mode. So, this is the type of thing you'd only really see in the uh in the higher, but you know, there good lessons for us all in here. That's why I'm going to do it.

[00:53:14]Okay, it says the initial temperature of the mixture was plus 20. The mixture froze at minus 1.5.

[00:53:21]Okay, it says a total of 165 kJ of internal energy was transferred from the mixer to cool and freeze it. Right, so this is really tricky. So don't get yourself put off if you're like no idea here. But this is provides us a good opportunity to revise what we've just said. Remember we said internal energy is the energy from the kinetic plus the energy from the potential. So that means right that that 165 K has gone to cooling it.

[00:53:58]Okay. And that's all to do with specific heat capacity and it's gone to freezing it and that's all to do with specific latent heat.

[00:54:09]Okay.

[00:54:12]So uh if I do both of those equations.

[00:54:16]Okay. So the civic heat capacity is energy equals mass time key capacity time temperature change and here is energy equals mass time uh specific lay heat. Those two added together will be 165 kJ. That's quite weird because what you're saying is this thing plus this thing is going to equal 165,000.

[00:54:47]And that's your insight to then work through it. Now, I'm not going to spend the rest of the time doing it because, you know, my class is foundation. I've got a lot of people here, but like and I think most of you are foundation. Um, but like that's that's our insight. And it's just the same equation stuff as before.

[00:55:06]Right. Um, does anyone have any particular topic requests? I've kind of done particles now. I did electricity earlier a bit. So now really it's uh energy or or the radiation stuff. I'll do a little bit of that.

[00:55:26]It's not going to be a long one tonight.

[00:55:27]So I'll probably do about 10 15 minutes more.

[00:55:31]Um unless people have particular questions energy please okay do you know the types of energy that's the first thing to know okay so way to remember the energy is kg cement okay yeah kinetic and stuff stuff like that right so these are all types of energy And again, I always like to think about them as like money, right? You know, you've got like pounds and dollars and euros, right? These are our currencies of energy. We've got kinetic.

[00:56:11]They're called energy stores.

[00:56:13]Gravitational potential.

[00:56:16]So that's the energy in being high up.

[00:56:19]We've got chemical. And the weird thing about chemical is is it comes up in different forms. So that could be in fuels because I can burn them. It could be in food because that's basically R for you all. And quite a weird one is batteries. Okay, batteries and cells are stores of chemical energy. They are not stores of electrical. Electrical is not one of these stores. Um uh I can have elastic potential. I can have magnetic, I can have electrostatic. So that's in charged particles. I can have nuclear and I can have thermal. Now, whilst these are all of the types of energy, overwhelmingly that one's common, that one's common, that one's common, that one happens occasionally, and that one's common. You mainly deal with them. Okay? Now, uh the other thing, uh we need to know how we transfer between them. Uh and the way to remember the transfers is Mr. Hehe.

[00:57:22]Okay. So, Mr. heat and uh you can transfer by mechanical.

[00:57:29]So that's like physically moving something, physically touching.

[00:57:35]Yeah. Yeah, I get you. I love a tip run.

[00:57:39]I love a tip run. I like going to the tip enough that when I see someone in the wrong bin, I can t at them.

[00:57:49]I'd say, "Oh, you don't want that there, mate. That goes in that one.

[00:57:58]Right. But yeah, your chem chemical goes in the other one, right? Because it's like it's like sto up. But it's so easy to think of it as like electrical, but it's not. Right. It's chemical and then it goes via the electrical pathway to whatever you're using it for. So if I'm looking at a phone, right? If I'm looking at the transfers in a phone, right?

[00:58:17]I have chemical in the battery and then that will end up as you know um thermal maybe okay phone gets hot you have some of it going off via the radiation pathway okay so that's light and stuff kinetic it makes the speakers move and sound move but this thing is happening via the electrical pathway That is not a type of energy. It's a way of transferring electricity. So by going the chemical going via electrical to thermal. Okay.

[00:58:54]Now the cool thing about this is if again if you like to think about it like money. Okay.

[00:59:00]What can you do with money? You you can't make you can't print money. Okay.

[00:59:08]So you can't create new money. You can't destroy money. The only thing you can do is change it. So, you know, you can exchange your efforts for money. You can if I've got 100 pounds, I can put it into dollars. I can put it into euros. I can change between them. Now, I know in real life they take a cut of it and stuff like that commission, but let's pretend that like we're a lovely perfect world. All right? So, the thing that you can only do with energy is transfer it.

[00:59:39]Now, what that means is is whatever energy I have before Right?

[00:59:44]It has to equal the energy after.

[00:59:47]That's such a fundamental idea. Like probably the most fundamental idea in the whole of physics like genuinely. And that's called conservation of energy.

[01:00:00]Okay? Think of conservation like the word conserve means to keep the same, right? Uh if I'm a conservative politician, I want to keep things the same back as I always were, right? If I work in animal conservation, I want to save. I want to save the animals. Make sure they're all nice and they're all the same. Okay. So, conservation of energy means I want to keep it the same.

[01:00:22]Now, where does that rear its head?

[01:00:24]Well, it rears its head often with transfers. So, um uh we can talk about efficiency, right?

[01:00:35]So uh efficiency again it's an equation which is given to us and uh efficiency is the useful energy divided by the total that you put in times by 100 to make it as a percent a percentage. So uh I don't know let's say I put uh 500 juwles into a light bulb.

[01:01:04]Look at that. I know what you're thinking. Are you doing art GCSE?

[01:01:08]Well, there's in the office. Um 500 drills in that. Let's say uh 50 of that goes as light that you like. Okay. And 450 uh is is thermal.

[01:01:22]So let's think about this. What is the useful energy? Okay. Well, the useful energy is the is the light that you want at the top. That's 50. The total energy is 500. That's what's going in.

[01:01:35]Okay. Times by 100 that would be 10%.

[01:01:39]Okay. Hello. Do you have any particular questions?

[01:01:45]Because I'm rambling here until people give questions. Only going to be about 10 15 minutes more. Um so that's uh 10%.

[01:01:59]Uh, I did the electricity earlier. Um, unfortunately, um, I'm sure you can scroll back on the live stream and see, you could try and pinpoint exactly where I lose my mind.

[01:02:13]Uh, some of you might say I never had it. Um, but I did a bit of electricity earlier.

[01:02:20]Um, so, uh, yeah, that's 10%. Now, good thing here, and this is What what I say always to to people is is have a sanity check. Okay? So about 10 minutes before the end, imagine that I storm into the exam hall and I go right sanity check.

[01:02:38]And what that means that you want to do is check, have you done the tick boxes?

[01:02:41]Have you done the fill in the gaps? And the other thing you want to do, especially here on a maths one, is does your answer make sense? Now this is efficiency. Now efficiency cannot be below zero and it cannot be above 100%.

[01:02:55]Okay? It's like a probability.

[01:03:03]I don't think you are clueless. I think you're probably less clueless than you think. I would say as long as you get happy with FIFA, right? Or however, you know, however you have been taught, but I would suggest FIFA uh doing equation questions, you will get an all right mark. Okay? Not saying you're going to like light the world on fire, but if you can do the equation questions, that's a skill. That's not something that you need to worry necessarily about revising because it's a skill, right? It's not it's not a bit of knowledge you need to remember off your heart.

[01:03:37]Um, so yeah, a good sanity check here would be like is have I done an efficiency and it ends up being over one or over 100%.

[01:03:45]It's like probability. That would be silly. I remember there was a question a few years ago where if you didn't change the units it was like how high would the toast pop out of a toaster and I had people put a thousand kilometers was the answer right but if you did a sanity check you'd be well obviously I'm not putting a thing down on a toaster and a toaster is being launched into space right it's obviously going to be like you know what a toaster is so so that's what I mean with like a sanity check um right I tell you What?

[01:04:19]Um, ramble with a little bit about energy.

[01:04:25]Let's do a couple of energy stuff or or let's do radiation. We haven't done any radiation and I feel like we've uh we've talked about radiation.

[01:04:35]Okay. Right before I ramble on that.

[01:04:38]Okay. There's actually three types of radiation. Okay. That you need to worry about. ion types of ionizing radiation and that is alpha, beta, and gamma.

[01:04:51]Okay. Oh, he's on fire. Right now, all of these are the idea of I have an unstable nucleus and it wants to get stable.

[01:05:03]Now, just like some of you right now, you're feeling a little bit vulnerable, feeling a little bit thing. How do you start to feel a bit better? You have a breakdown.

[01:05:11]Okay.

[01:05:12]Now, it turns out that when atoms break down, they're all ionizing. Yeah, they're all ionizing. Um, when they have a breakdown, atoms can do it in three ways. They can do it in the way that we call alpha, the way that we call beta, and the way that we call gamma. This is just ABC in Greek because scientists like to pretend that they're really clever. Okay? It's all it is. It's literally ABC.

[01:05:32]All right? Now alpha okay is where it breaks down by losing a lump which is two protons and two neutrons okay so this is made of two protons and two neutrons now because of that it's often called a helium nucleus.

[01:05:52]Okay.

[01:05:55]All right. Now beta is where we lose a little electron and it's not from the outside where we think electrons are.

[01:06:01]It's an electron, but it's weird. It comes from the nucleus, right? It's an electron from the nucleus. It's like a fast electron.

[01:06:13]And then gamma, I know it's in paper, too, so you don't have to worry about it, but you know when you do waves and you do radio waves, microwaves, infrared radiation, all of that fun, right? That is the same thing there. That's an electromagnetic wave.

[01:06:30]It's a high energy electromagnetic wave.

[01:06:33]Now, here's how I like to think about, and please do not write this in the exam. I always think about alpha as like a sumo wrestler. I think of beta as like a year seven. And I think of gamma as like a ghost. Right? Now, this is a big big old lump. Two protons, two neutrons. It's heavy. Okay? Okay, it's mass is four big huge.

[01:07:01]All right. Now, just like a suma wrestler, if they run into you, that's going to cause a lot of damage. Now, we call that its ionization power, right?

[01:07:10]Because we're measuring how much it it will knock electrons off atoms and turn them into ions. And the ionization power of alpha is really high because if I ran into a suma wrestler, he's going to send me flying.

[01:07:25]Okay.

[01:07:27]Now, how far does it go? This is where we come to something called penetration power. Now, if I was being attacked by a suma wrestler, actually quite easy to get away from. You just jog slightly in the other direction. He runs out of breath. Easy. Okay. So, if he hits you, big damage, right? But it's easy to get away. It's the same thing with alpha radiation. If the alpha radiation is say inside you going to cause loads of damage, right? If it's in a gas and you breathe it in, right? It's an alpha source starts making alpha radiation problem. Okay?

[01:08:05]But it's actually easily stopped. It's stopped by paper. It's stopped by only a few centimeters of air.

[01:08:12]And that's actually why we use alpha in smoke alarms or we used to because it would get stopped by the smoke and it would trigger the smoke alarm.

[01:08:20]Now I said beta. Let's imagine it's like a little year seven. Now, their math is actually very small. It's about one divide by 1,800. Just like a little small year seven. They're they're nippy.

[01:08:29]They're wily. Okay? They start thinking they're rebels. They'll run the wrong way wrong way down a oneway system, right? All of this stuff, right? And maybe, you know, if a supply teacher comes out or something, okay, they'll ignore him because they think they're mad lads, right? And they'll run through, okay? If they hit into you, they're annoying, right? They're not going to cause big damage like sumo, okay? But they're going to cause like a medium amount of damage. Right.

[01:08:57]But their penetration power is again we can think of it as as kind of medium.

[01:09:02]This we need something a little bit more solid to kind of stop them getting away.

[01:09:06]And that we tend to typically say aluminium.

[01:09:09]Okay.

[01:09:11]And then finally gamma. Gamma, right?

[01:09:14]It's like a ghost. It mass is literally zero.

[01:09:17]Okay. Now gamma it ionization power is actually quite low.

[01:09:22]Right? Because if ghosts move through you, you go, "Oh, right." You go, "Oh, what's going on there?" Not that ghosts exist, but that's a debate for another time. But they'll go through everything.

[01:09:31]They're penetration power is really high. To stop them, we need something like thick lead.

[01:09:36]Okay?

[01:09:38]So, we kind of got this tradeoff. If you imagine that you've got high ionization and low penetration for s for the for the alpha particle, then it kind of flips. All right?

[01:09:49]So, we've got alpha, beta, and gamma.

[01:09:51]Now, at foundation level, they straight up like to ask about the stats, right?

[01:09:55]What one's got the highest penetration power? That's gamma. Okay. What one has um is stopped by element minium beta.

[01:10:07]Okay. Um see good one.

[01:10:21]Yeah. So look look at this. What a question right? What a long answer question. It says explain the differences in properties of alpha beta and gamma radiation. So it's explain. So that means you need to say why.

[01:10:34]Okay.

[01:10:36]Right. So it's not just like what is going on. It's not describe. Okay.

[01:10:41]Saying why. Okay.

[01:10:43]And remember you can answer in bullet points. Okay. So let's think about alpha. Okay. What is it that we know about alpha?

[01:10:52]Okay. Alpha the properties of it.

[01:10:57]Okay. is it has high ionization power.

[01:11:06]Why is that? Okay.

[01:11:10]Because it's a heavy particle.

[01:11:15]Okay. It has low penetration power.

[01:11:22]Again, that's because it's a heavy particle.

[01:11:25]Okay. You could say it's deflected.

[01:11:29]by uh electric field. It's quite weird. That's because it's that is two plus, right?

[01:11:39]So, it's got a charge. That's because it has a charge.

[01:11:46]Okay. And what beta like?

[01:11:49]Well, beta is a medium. Okay. So you could say even say that this is a is because it's a helium nucleus, right? Beta is got a medium ionization power.

[01:12:05]Okay, it's uh stopped by aluminium.

[01:12:14]Okay, why is that the case?

[01:12:17]This is because it is a fast moving electron.

[01:12:26]You're linking it back to what it is.

[01:12:29]They are all ionizing. Absolutely. Yeah.

[01:12:33]Just a different levels.

[01:12:35]Okay.

[01:12:37]Um but because it talked about differences, that's why I'm kind of not going to say they're all ionizing because that would imply similarity.

[01:12:45]Okay. Okay, we're just focusing on the difference.

[01:12:48]And then I've got gamma.

[01:12:51]Okay, well gamma, okay, has got low ionizing power.

[01:12:59]Okay, it needs thick lead to stop.

[01:13:04]So I'm answering this like I'm like running out of time at the end of the paper, right?

[01:13:10]Okay, why is that? Okay. It's because it's a high energy electro magnetic wave. Right. And I scrambled an answer there in the last two minutes.

[01:13:24]Okay. And I'm home for tea and cake.

[01:13:28]Um, right. Another little kind of idea just to think about here is is these nuclear equations. Um, and the thing about nuclear equations is, uh, and my advice is to imagine that there's like a little equal sign there with like a little invisible equal sign.

[01:13:52]Okay? And whatever I have on the left, I've got to have on the right, just like I would in a in an equation. All right?

[01:13:57]So, if I've got 89 here, that means a plus whatever number is there, okay?

[01:14:03]It's got to equal 89. Okay? So let me do a different one just as an example.

[01:14:08]Right? So let's say I've got uranium 238.

[01:14:13]Okay. Now this actually does alpha decay. And given what we've said before here, alpha is two protons, two neutrons. So like a helium nucleus. So I'm going do a little alpha symbol. And it would have a top number of four and a bottom number of two. So given what I've said, whatever I have at the top, what I have there. So 238 equals something + 4.

[01:14:36]Well, that's going to be 234 because 234 + 4 is 238.

[01:14:41]And again down here, something + 2 is equal to 92. That's going to be 90. And again, they're not you're not expected to be able to find it on the periodic table, but you would you would see that that's uh that's four in TH. So if I look over here, beta, it turns out the stats of the particle is zero on top and minus one. So 89 equals something plus 0. Well, that has got to be 89, right? It's got to be the same. Plus 0 means that's 89. This is the beta is the hardest one for these equations. And you can see here why because people easily go I take that minus one and that'll be that. But 38 equals whatever number that is minus one. That actually means that that's got to be 39 because 39 minus one is 38. So that would be 39. That's quite tough.

[01:15:34]Right. The last thing I'll do before I hit off, okay, is there was a halflife question.

[01:15:46]Okay.

[01:15:47]Now uh oh the other one is contamination versus radiation. Uh contamination is the unwanted presence of the material.

[01:15:59]So that means it is physically on you and ioniz radiation is simply you're being exposed to it. So in this question it says radioactive dust from the nuclear weapons testing settled on the desert. So that means it's physically on the desert and that means it's contamination.

[01:16:17]Okay, if I was stood there watching a nuclear bomb go off, right, and I got the radiation kind of hit me in the face, that means that I would be I would have been radiated. If I then start breathing in all the radioactive dust, that's contamination. Okay.

[01:16:34]Um, now we then get this thing called halflife. Okay.

[01:16:41]Now halflife is basically the time it takes to have right be that activity be that number of atoms. So can you see here the activity is 80.

[01:16:56]So to have it would have to get to 40.

[01:17:01]And if I read across to 40 and I read down here, that would give me 12.5 years as our half life. Now in another 12.5 years, okay, it will have halved again. So after 25 years, it will be at 20.

[01:17:27]Okay? and after another 12.5 years it'd be at 10 and after another 12.5 years it' be at five. So it's permanently this h havinging business.

[01:17:37]Okay. So you can see here on foundation they tend to hold your hand through it.

[01:17:41]Right? How much time did it take for the activity of the sample to decrease in age 40 that's 12.5 years. You can see it from my from my thing. Now here's your last kind of question spot thing. If you have something like this where there's no line of working out the answer can be two things. It's either same as above or it's zero. Now, given the fact we've gone from 8 to 40, that suggests that it's got to be the same as above. It's 12.5 years. Okay. Or because I've written it in that thing in my flusterness, I've gone 12.5 years years.

[01:18:17]Cool. We'll call that ramble over. Um, does anybody have any final questions before I uh bid you?

[01:18:36]So, I appreciate it's been a bit rambly.

[01:18:38]Anyone have any final questions?

[01:18:57]It's nice to get peak viewership cuz I'm about to go on it. Um, right. Uh, hopefully that was uh um useful in any way, shape, or form. Uh, it was a bit of an annoying start uh with my computer crashing and stuff. Um, and you know, I think I'm a bit tired myself. Um, just relax into it. Um, remember to follow FIFA.

[01:19:22]Do your equations to the best of your ability and I'm sure it'll be okay.

[01:19:27]Okay, you're getting there. Two weeks left. That's it. And you're all done.

[01:19:34]And you have the best summer ever.

[01:19:37]Okay. Right. Thank you very much. And have uh good luck. Have a lovely rest of your evening.