91�ȱ�

Rohan You need structure in your day for revision. It really helped me to get my head down.

Lauren So when I first started revising for my GCSEs, all I did was re-write out the notes I already had. About three months into it, so I wasted three months of revision time, I was no further on with my knowledge or anything, than what I was to begin with, because I wasn't doing active revision. I was just writing everything that I could see.

Rohan I had this technique, which was called look, say, cover, write, check, which essentially meant that you know, you look over the content, you cover over it, you say out loud, you write it down and then you check it. Going through that, it really helps you just solidify information in your head.

Baxter So I have dyslexia and reading in my head, it didn't really help. So reading it out loud really helped me remember key words.

Jacintha Doing active recall or testing yourself with flashcards can be very helpful, especially if you do it with friends, as revising can be quite an isolating event.

Milly Before an exam I think it's really fun to test your peers and what you know. Playing them games helps with that active recall before the exam and helps you see what key information you couldn't remember.

Niall For me, I put a mind map at the start of each jotter, just so I kind of know what I need to revise, so I can like tick it off, what I've done and what I need to do.

Rohan I love using mind maps because at the start of every topic, I like to write down everything that I know and then fill in any gaps later on.

Milly When I've been revising, I do like to use drawings, for example, the wall cycle. I like to draw that out and use words underneath to explain what's going on.

Jacintha If you struggle to study alone, doing video calls with a couple of friends when revising can really help. You can all go through the same exam paper and exam questions, and help each other with your answers. Make sure to choose your friends carefully so you don't distract each other.

Nung With my sensory overload that I've experienced quite often, I revise in smaller chunks, and kind of focussing on it for like 20 minutes, giving myself a break and then come back to it. But also, I have like a fidget toy that always had on me, because it helped me to focus.

Lauren I used sticky notes for stuff like French and English lit, so I would write down quotes, I would write down French tenses, verb endings, anything you can think of.

Jacintha I found it so helpful to embed Spanish in my daily life. For example, saving my parents under madre and padre in my phone, instead of mum and dad. Also, watching Spanish shows with English subtitles helps you get used to the language and the accent.

Shay I think everyone revises differently, and it's really important to remember that while you're doing your own studying. Find out what your own weaknesses are and work on them.

Jacintha There are lots of ways to revise, so figure out what's best for you.

Josh Revising is a skill, and there are loads of ways that you can up your game.

Dr Vanessa Make sure you know which topics you need to revise for each subject. Check with your teacher about your exam board specification for this year and use that as a revision list. Separate your revision notes into subjects right at the start.

Dr Colton Use exercise books, textbooks and revision guides. Don't rely on your lesson notes only ,in case you've missed something.

Dr Vanessa Making flashcards, rather than just re-reading your notes helps you practise remembering the information, just as you will need to do during the exam.

Dr Radha Movement breaks are brilliant. Give your brain extra stimulation by moving your body and working your muscles.

Josh Keep a log of what you feel you have achieved, even if this is just crossing off a checklist. You'll be amazed how far you have come. Mock exams the best form of practise. Aim to do as much revision for those as you do for an actual assessment. Try and replicate exam conditions, so set a timer and go for it.

Dr Colton Every subject is different and your teachers will have really good advice on how to maximise your time. So take on board what they're saying to you and incorporate it into your personal study.

Dr Vanessa Be as proactive as possible with your revision. Use lots of different methods of materials. Check in with your teacher that you're revising the correct topics and keep track of your progress. People are not naturally good or bad at exams. It comes down to technique and practise at the end of the day.

Dean McCullough Hello. I'm Dean McCullough from 91�ȱ� Radio 1. And here's how I would create my chilled out revision playlist. I'm talking songs that are going to get you in the mood, but are not going to distract you so I would create songs that are going to make me feel good, make me feel empowered, but are not going to distract me.

And here are some of the artists that I would include: I am obsessed with Arlo Parks, there's something about her music and lyrics that takes me to a happy place. And that's kind of what you need when you're revising. I also love Olivia Rodrigo. Holly Humberstone and you know what, I'm gonna put Blossoms in there because, let's be honest, you need music that's going to make you feel energised, we wouldn't wanna be falling asleep when we're revising, so a bit of Blossoms in there, I'm all right with that.

And then I do like my chilled out pop. I'm gonna throw Ed Sheeran in here. Ed Sheeran for me, I can have him on in the background. I feel like he's not too distracting, unless we get into Galway Girl and then suddenly I'm in a bar. So yeah, I'm going to keep those guys in there as well. And if you want someone else to do all the hard work for you, genuinely head on to 91�ȱ� Sounds. There are loads of relaxing playlists on there. You've got the Radio 1 relax stream which is 24/7 of really chilled out, beautiful tunes - there's something in there for everybody. Or you can listen to the Chill show. There are bands and artists and DJs from all across the world whose job it is to create these playlists exactly for this and I believe there is a revision playlist on there as well. So go and check it out.

Carl: Hello, and welcome to the Bitesize English literature podcast.

Jean: I'm Jean Menzies, author and ancient historian.

Carl: I'm Carl Anka, journalist and author.

Jean: We're here today to help you dive a little deeper into some of the texts in GCSE English literature.

Carl: It's worth noting that there will be spoilers in this as we look into each text as a whole. So if you're not quite finished reading, or you're not quite ready for spoilers, just come back later.

Jean: There's plenty here to get your teeth stuck into.

Carl: Now, you've clearly done something right, because you've made it here. If you want to hear all the episodes in this podcast, make sure you download the 91�ȱ� sounds app.

Jean: And don't forget that whilst you're in the 91�ȱ� sounds app, there's loads of other things you can use to help you with your revision – full versions of some of the texts you might be studying, revision playlists, and other Bitesize podcast series to help with different subjects. In this series, we'll be covering some of the key things you need to know about Macbeth: the plot, the characters, the themes, and the language Shakespeare uses.

Carl: In this episode, we're going to look at the plot of Macbeth and I'm going to tell you something now Jean - Macbeth is my text. This is one of my favourites and I'm very excited to take a closer look at some of these key moments. Is it weird to say Macbeth is one of my favourites?

Jean: Absolutely not - there is so much to keep you hooked in this play. I completely get it.

Carl: Let's get into this one then.

EXTRACT
Macbeth: Speak, if you can: what are you?
First Witch: All hail, Macbeth, hail to thee Thane of Glamis.
Second Witch: All hail, Macbeth, hail to thee Thane of Cawdor.
Third Witch: All hail, Macbeth, that shalt be King hereafter.
Banquo: Good sir, why do you start, and seem to fear things that do sound so fair?

Carl: Right, we've stepped inside the story. And straight into Act 1 scene 3, where Macbeth has encountered three witches for the very first time. Now, Macbeth is the Thane of Glamis. And I should probably say at this point in time that a thane is a nobleman who owns land that's been given to him by the king in exchange for his military services. Macbeth is on his way home from a battle with his best friend Banquo, where they've been successful against the Norwegians. Macbeth in particular has played a huge role in that success. He’s killed someone. He chopped him from his chin down to his belly button. So yeah, very early on, we find out Macbeth is a good fighter - big, strong lad. And on the way back with him and Banquo they meet the three witches who predict a number of things, including that Macbeth will one day become the King of Scotland.

Jean: I mean, seriously, what would you do? You're heading home today and three witches stop you and tell you that one of your greatest dreams is going to come true. I mean, you think they were trying to wind you up, wouldn't you?

Carl: Yeah, it would be my first thing. But then the witches tell them a number of things. They first greet him as the Thane of Glamis, which is what he already is. And then they predict he's going to be the Thane of Cawdor, and then they say he’s gonna be the King of Scotland afterwards. They also tell him that the sons of Banquo will be king one day as well, which is interesting. He doesn't think any of these predictions will come true. The first one comes true, like that - pretty much the moment he gets home, he finds that he's gonna be made the Thane of Cawdor when King Duncan awards it to him for his victory in the battle. So then Macbeth, the cogs start turning, Macbeth begins to wonder if the other predictions will become true.

Jean: And Macbeth is an ambitious man. So for this to feel like a possibility must be really exciting for him.

Carl: Macbeth’s wife, who is referred to as Lady Macbeth, is even more ambitious and ruthless than Macbeth is. So, once when Macbeth tells her about the witches’ prophecy, Lady Macbeth is fully on board with the plan for Macbeth to become king, which also includes a little spot of murder. She says, you know, maybe you should murder Duncan, when Duncan comes around to visit Macbeth in Macbeth’s castle.

EXTRACT
Macbeth: Is this a dagger which I see before me, the handle toward my hand? Come, let me clutch thee. I have thee not, and yet I see thee still.

Jean: You can’t discuss the plot of Macbeth without hearing this line - “Is this a dagger which I see before me”, one of the most famous lines of the play, and of Shakespeare's actually.

Carl: This is just at the point where Macbeth is on his way to do the deed and murder Duncan, when he sees a dagger pointing him in the direction of the king. We don't know if it's a hallucination, but moments after saying this Macbeth takes his own dagger from his belt and commits the deed. He murders Duncan. He hesitates just before he does it, but Lady Macbeth is very encouraging saying they have to go through with their plan.

Jean: Such a supportive spouse.

Carl: Of sorts…

Jean: So it's Macduff who finds Duncan murdered but Macbeth and Lady Macbeth are able to use the king's guard as a cover for their crime. Meanwhile, Duncan’s sons disappear as they're scared for their lives, which means…

Carl: Dun dun dun dun dun. Macbeth becomes the King of Scotland, just like the witches said he would.

EXTRACT
Banquo: Thou hast it now: King, Cawdor, Glamis, all,
As the weird women promised, and I fear
Thou play'dst most foully for 't.

Carl: That extract that we just heard there - that is Banquo, Macbeth's best mate. He was there the day the witches told Macbeth about the prophecy, and he knows that everything isn't as what it seems.

EXTRACT
Banquo: And I fear Thou play'dst most foully for 't.

Carl: Now, what does that mean? You may have heard the term foul play. That is a sentence that is all about violence and murder in certain crimes. Banquo is suggesting that he's suspicious about Macbeth’s involvement in the death of King Duncan. Now, we, the audience and the reader, know that Banquo's suspicions are correct. Macbeth did do a murder - Banquo's not totally sure. And then Macbeth decides something needs to be done about it.

Jean: He does another murder, obviously, because killing people is clearly what he does now.

Carl: Yeah. The first Macbeth that you meet when the play starts, Macbeth did murders but he was doing it in service of his king in battle. And this was described as noble, and to help his country of Scotland. But now, as things progress and Duncan has been murdered, and now that Banquo has been murdered, Macbeth is entirely self-serving. He's using violence and murder to push himself forward and to put others down. The whole play of Macbeth is about how ambition and the love of power can destroy someone and those around him. Right? This is something we're hearing unfolding every single scene. Banquo was Macbeth’s best friend. But Macbeth turns against him, because Macbeth’s need for power and the need to protect his own power warps him. And there's also Lady Macbeth, who helps convince him again and again that these deadly decisions are the right things to do.

Jean: And he has changed and started committing these acts of absolute evil since he heard the witches’ prophecy. But there's reasons to think that there could be guilt there, too. I mean, one of the interpretations is that he feels so guilty that he actually sees the ghost of Banquo later on. And because he's the only one who can see him, those around him start to wonder if he's imagining it, including Lady Macbeth.

Carl: There's a decent argument to be made that he doesn't actually feel guilty at all. And that he’s driven as a consequence of his sin of killing the king. People in the Jacobean era, which is the era between 1603 and 1625, believe that what behaviour was going on was punishment for Macbeth’s sin.

Jean: Either way, the witches have a lot to answer for, but Macbeth wants to know more from them.

EXTRACT
Witches: Double, double toil and trouble. Fire burn and caldron bubble.

Carl: And there's the other famous line: “Double, double toil and trouble, fire burn and cauldron bubble.” I love this line, so so much. It's the one that a lot of people quote when you say, “Oh, I'm studying Macbeth.”

Jean: I'm not even sure everyone remembers it's from Macbeth. I mean, why would you, it's in so many other pieces of pop culture as well, but that is where it comes from. It's just a really popular line now that's synonymous with witches and spells. So Macbeth has come back to see the witches here, and they tell him three things. Beware Macduff, the Thane of Fife. None of woman born shall harm Macbeth. And Macbeth shall never vanquished be, until Great Birnam wood to high Dunsinane hill shall come against him.

Carl: Now these are slightly more complex prophecies than the first batch. Especially because two and three are supposed to be logically and physically impossible. None of woman born can harm him and a forest physically moving location, so it can hurt Macbeth makes Macbeth feel safe. Well, those things certainly can’t happen. I'm absolutely cushty. But it's the first prophecy. Beware Macduff - that comes true quite quickly, because Macbeth finds out that Macduff, Thane of Fife, has gone to join Malcolm who is Duncan’s son, in England. So what'd you think Macbeth is gonna do about this prophecy?

Jean: Yep, you've got it. He does a murder. He seizes Macduff’s castle and has his wife and children killed. This in particular feels as if it's the most brutal murder up until this point in the play. But that does not prove to be a smart move, because Macduff is quite obviously devastated, and therefore vows to have revenge.

Carl: That's the thing about Macbeth. There is so much going on all the time.

Jean: Yeah, it really all is happening. And there's still a lot more to come. Because we haven't heard from Lady Macbeth for a while. That's because her own guilt has actually started to take its toll on her and she's sleepwalking around the castle, remembering all the evil things she's done.

Carl: Although that's the same thing we said about Macbeth. Some Jacobeans will believe that guilt is happening to Lady Macbeth. And some believe that this is insanity happening to Lady Macbeth as well.

EXTRACT
Lady Macbeth: Out, damned spot; out, I say!

Carl: So that we just heard now, “Out, damned spot” - that is one of the most famous speeches from Lady Macbeth. It's Lady Macbeth referring to imaginary blood that she can see on her hands. She can't get away from the guilt and responsibility for all the deaths that have occurred, and she's having a breakdown. In Act 5, the final act of the play, Macbeth finds out that Lady Macbeth has died. It’s never fully explained how or why Lady Macbeth died. And Macbeth himself seems pretty resigned, uninterested. There is a small suggestion that Lady Macbeth may have taken her own life. And it's also some suggestion that basically, Macbeth doesn't care anymore. It is the tragic downfall, so we began this play with so much determination. But we know that Macbeth is all about ambition. And we know how love of power that motivated Macbeth and Lady Macbeth in the beginning is detrimental to both of them in the end.

Jean: Act 5 scene 6 - Malcolm and Macduff’s invasion has begun. At this point, Macbeth still thinks he's protected by the witches' predictions, but he's wrong. When the invading army cut down the trees in Birnam wood to use as camouflage as they move to Macbeth's castle in Dunsinane, it seems as though the trees themselves are moving, and thus making the third of the witches’ latest prophecies come true.

Carl: So they said that Macbeth will never be beaten until the woods moved, and here they are. Right?

Jean: Exactly. It's such a clever way to make that come about. I absolutely love that revelation in that moment in the play.

EXTRACT
Macbeth: I bear a charmed life, which must not yield,
To one of woman born.
Macduff: Despair thy charm;
And let the angel whom thou still hast served
Tell thee, Macduff was from his mother's womb
Untimely ripp'd.

Carl: It's one of the greatest twists ever written I think, this one, because when you read it, that he can't be harmed by someone born of woman, you have no idea where Shakespeare is going with that. Are the witches lying? Are they trying to bring him down? And then Macduff answers them easily. He was from his mother's womb untimely ripped.

Jean: I know, another seriously clever way to spin that that I never could have come up with. I remember the first time I read that. And you're right. It's that moment, like when you're watching a great thriller, and it takes an unexpected turn that has you shouting at the TV. So Macduff was untimely ripped from his mother's womb. So we can assume, delivered by Caesarean rather than born of woman in the traditional sense. So he's able to kill and behead Macbeth. Malcolm becomes the new King of Scotland and we hear how accepting the witches' prophecies leads directly to Macbeth's downfall.

Carl: So, thank you for listening to Episode One of the Bitesize English literature podcast. And joining us as we explored the plot of Macbeth.

Jean: Well, there's actually still a lot more to learn. So take a listen to the rest of the episodes of the Bitesize English literature podcast on 91�ȱ� Sounds to find out more. In Episode Two we'll be taking a look at some of the characters from Macbeth, particularly Macbeth and Lady Macbeth.

ELLIE: Hello and welcome to the 91�ȱ� Bitesize Physics podcast.

JAMES: The series designed to help you tackle your GCSE in physics and combined science. I'm James Stewart, I'm a climate science expert and TV presenter.

ELLIE: And I'm Ellie Hurer, a bioscience PhD researcher. We're covering lots of different aspects of forces in this series, so make sure to listen to the rest of the episodes too.

JAMES: Yeah, and they're really good. Okay, let's get started because today, I thought so, because today we're talking all about the force that keeps our feet on the ground, gravity.

ELLIE: While we often think about space and astronauts when we talk about gravity, gravity actually acts all around us every single day. Because the definition of gravity is a force of attraction between two objects.

JAMES: The gravitational field is the area around an object where another object will feel a force of gravitational attraction from it.

Gravitational field strength is measured in newtons per kilogram, written out as ‘n’ forward slash ‘kg’.

ELLIE: And the size of the gravitational field strength affects the force of gravity acting on an object in that gravitational field. The other thing that affects the size of gravity is the object's mass. The bigger the mass, the greater the force of gravity.

JAMES: So one key thing to know that a lot of people misunderstand is that weight and mass are actually two different things.

ELLIE: Yeah, so when we say, oh, this loaf of bread weighs 400 grams, we're actually saying that the mass of the loaf of bread is 400 grams.

JAMES: Because mass is about the amount of matter, whereas weight is a force and is the heaviness due to gravity.

ELLIE: Exactly. So let me tell you about the equation you need to calculate the force of weight of an object.

JAMES: Yeah, I'm gonna get my pen and paper out for this one, so if you're listening, please feel free to do the same thing and write along as we go through this.

ELLIE: So, weight equals mass multiplied by the gravitational field strength.

JAMES: Weight is measured in newtons. Mass is measured in kilograms and gravitational field strength is measured in newtons per kilogram.

ELLIE: So to calculate the weight of an object in newtons, you multiply its mass in kilograms by the strength of the gravitational field in newtons per kilogram.

JAMES: That was a lot. Don't panic. Let's just hear that again.

ELLIE: So weight equals mass multiplied by the gravitational field strength.

JAMES: Weight is measured in newtons, mass is measured in kilograms, and gravitational field strength is measured in newtons per kilogram.

ELLIE: So, to calculate the weight of an object in Newtons, you multiply its mass in kilograms by the strength of the gravitational field in Newtons per kilogram.

JAMES: Right, let's try out some examples then. And if you don't have your pen and paper just yet, now would be the perfect time to grab them and you can write down these calculations with us as we go along.

ELLIE: Let's say we want to find out the force of gravity, their weight, acting on your physics teacher as they stand at the front of the classroom.

JAMES: Good image. Now first, you would need to find out their mass. Now let's say it's 80 kilograms, then you need to know the gravitational field strength of the planet they're standing on, which for the planet of Earth is 9.8 newtons per kilogram.

ELLIE: So to measure the force of weight acting on them, you would write down their mass of 80 kilograms and then multiply it by the Earth's gravitational field strength of 9.8 newtons per kilogram to get the answer 784.

JAMES: And because weight is measured in newtons, their weight would be 784 newtons downward. We always have to include those units. And because weight is a force, which is a vector quantity (more about that in episode one), we also have to say the direction it is in, which in this case is downwards.

ELLIE: In those instances, the weight of an object and its mass are directly proportional. So let's say if something had a bigger mass, its weight would be higher. And if something had a smaller mass, its weight would be lower.

JAMES: Exactly. And when we're measuring weight in terms of gravity, we don't use regular kitchen scales. We use something called a newton meter, also known as a calibrated spring balance.

ELLIE: And when we do that, we say that the weight of an object, or in this case, person, acts at a single point. The object or person's centre of mass. The force of gravity, weight, always acts from the middle of an object, straight down.

JAMES: Okay, that was a lot, but I hope that helped you understand gravity a little bit more.

ELLIE: So, let's recap the three main points.

Firstly, gravity is a force of attraction between two objects. The next point is, mass is the amount of matter in an object. However, weight is the force of gravity acting from the middle of the object straight down.

And finally, the equation to find out an object's weight is mass multiplied by gravitational field strength equals weight.

There's your key points about gravity. In the next episode of Bitesize Physics, we're going to dig into work done and energy transfer, and I cannot wait.

JAMES: I believe you. Thank you for listening to 91�ȱ� Physics. If you found this helpful, and hopefully you did, please do go back and listen, make some notes, so you can come back here and always have this as your point to revise from.

JAMES: Thank you, bye!

ELLIE: Bye!

Hello, I’m Dr Alex Lathbridge and this is Bitesize Biology.

In this podcast I’m going to take you through the main things you need to know for your GCSE Biology exam.

I’m going to be talking about things as small as cells, as big as rainforests and everything in-between.

There’s going to be a lot for you to remember. And as we go through all of the topics, there will be a few key terms that you’re going to need to learn off by heart. But don’t worry, I did it, you can do it too.

This is the is the first episode of a nine-part series on The Cell, let’s go.

All living things are made of cells, which is why they’re called the building blocks of life.

Plants are made of cells, animals are made of cells, humans are animals so even you, yes you, are made of cells.

In fact, right now, you are a giant, complex container made out of trillions of cells all working together, to learn about cells.

Anyway, today we’re going to take it back to basics and find out about the structure of the cell and the two main types that you are going to need to know.

The thing about cells is that they are small, like really, really small.

Anything between 0.01 and 0.1mm across.

This means they are too small to see with the naked eye. In order to study them properly, scientists first had to invent really powerful microscopes in order to see what’s inside them.

If this is all new to you, don’t worry, scientists like me are learning stuff all the time too.

Nearly all cells have four key things in common:

1. They have a membrane. This holds the cell together, keeps its contents inside and controls what can enter and exit the cell. Think of it like a balloon that can let things in and out.

2. They have a cytoplasm, which is kind of like a really useful jelly. It’s where all the chemical reactions take place in the cell. Think of it like water inside that balloon.

3. They have DNA. DNA is genetic material. And it contains all the information that tells the cell what to do, your cells following all these instructions is how you develop and grow.

4. They have ribosomes. These are sort of like mini-robots which make proteins based on the instructions found in DNA.

So, you could say that a simple cell is just a tiny a water balloon, filled with instructions and little protein-making robots.

Or, if you want to pass your exams, you could say that a cell is between 0.01 and 0.1mm across and made of a cell membrane containing cytoplasm, DNA and ribosomes.

Now, there are two types of cells you’ll need to know about:

Eukaryotic and prokaryotic cells.

You are a eukaryotic organism. This means that you are made up of lots of different types of cells, most of which have a nucleus.

These kinds of cells, the ones that work together with lots of other kinds of cells to make up a plant or animal or human, are called eukaryotic. Easy to remember: because you are eukaryotic.

Let’s think about most eukaryotic animal cells. As well as the stuff we’ve just talked about (that water balloon) most eukaryotic cells also have a nucleus.

Remember that cells always contain DNA? Well, in eukaryotic cells, the genetic material is kept inside a nucleus. Think of it like a little folder.

And they have Mitochondria. This is where cells release the energy they need, that’s where respiration takes place. Think of them like little batteries.

So, when it comes to most eukaryotic animal cells, we’ve got our water balloon (a membrane filled with cytoplasm), containing instructions to make proteins inside a little folder (DNA inside a nucleus), robots to synthesise the proteins (ribosomes) and batteries to power the whole thing (or mitochondria).

And just because things are never that simple, in animals red blood cells are the exception because they don’t have a nucleus.

It’s worth drawing it out, I've always found it useful, even just a quick doodle. Remember, there are lots of diagrams on the Bitesize website. It might be useful to look at those while you listen.

Now, although you might think you are a little bit more interesting than a lettuce, most eukaryotic cells in plants have some extra stuff on top of all that. So, plant cells have a membrane, cytoplasm, DNA, a nucleus and mitochondria and:

1. They have an extra layer outside of the cell membrane called the cell wall. Plants need a cell wall because they need to stand up straight, but they don’t have a skeleton, and this is where the cell wall comes in, it helps keep plants upright.

2. Green cells in plants’ stems and leaves have chloroplasts, which contain chlorophyll and the enzymes needed for photosynthesis. Photosynthesis is really important and we’re going to come back to it later in the series, but for now what you need to know is that chloroplasts contain the stuff that plant cells use to store energy from sunlight. Think of it like a little solar panel.

3. They also have a permanent vacuole. You can basically think of it like a little pocket inside of the cell, filled with something called cell sap that helps to keep the cell in shape.

And remember how red blood cells don’t have a nucleus? Most plant root cells don’t have chloroplasts, so they’re white not green.

Ok, so that was eukaryotic cells. Now let’s look at prokaryotic cells

Prokaryotic cells are always single celled organisms.

Like bacteria. The whole organism is just one tiny cell that does it all.

But just because it’s small doesn’t mean it’s not important. We need bacteria in our guts, to help us break down food and the environment is the same, the life cycle of things dying, and their nutrients being returned to the earth depends on bacteria.

This is why you should be very pro prokaryotic cells.

Like all cells, prokaryotes have a cell membrane, cytoplasm, DNA, and ribosomes.

However, there are two main differences:

1. Firstly, the DNA isn’t inside a nucleus, instead it floats free inside the cytoplasm in a single circular loop of DNA, with some extra little bits of circular DNA called plasmids.

2. Secondly, prokaryotes also have a cell wall, outside of the membrane.

And yeah, all cells are microscopic but there’s a big difference between eukaryotic cells and prokaryotic cells.

So eukaryotic cells, plant cells and animal cells, can be anything from 10 to 100x larger than prokaryotic cells, found in single celled organisms like bacteria.

I’m Dr Alex Lathbridge and this is Bitesize Biology. To hear more, search Bitesize Biology on 91�ȱ� Sounds.

SUNAYANA: I’m Dr Sunayana Bhargava, a scientist and poet.

TULELA: And I’m Tulela Pea, a science communicator and podcaster.

SUNAYANA: And this is Bitesize Chemistry. This is the second episode in an eight-part series on atomic structure and the periodic table. In this episode, we’re going to look at the history of the atom and how that model has developed over the centuries.

TULELA: We’ll look at how this led to our understanding that atoms are made up from protons, neutrons and electrons.

SUNAYANA: And we’ll end with a quick summary of the main important facts for you to take away because life is just so darn busy these days.

TULELA: But also because that’s why we’re here after all - to help revise GCSE chemistry and combined science.

SUNAYANA: Our chat bot NNICK is with us again.

NNICK: Oh, I love Chemistry, I adore it, divine chemistry!

SUNAYANA: Before we unleash NNICK, what I like about the history of the structure of the atom is that it’s a really good example of how science works. You come up with a new idea or hypothesis, devise an experiment to test the hypothesis and if the evidence backs up your predictions then it becomes a better theory. And our understanding is a little better than it was before. And this is exactly true with how the model of the atom has developed throughout history.

TULELA: Totally! So if we begin say only 200 years ago, back then what we thought an atom looked like was actually quite basic, tiny.

SUNAYANA: Very, very tiny.

TULELA: Very, very, tiny spheres that can’t be divided. This idea was proposed by a scientist from Manchester called John Dalton in 1804.

SUNAYANA: Actually, it kinda goes all the way back to the ancient Greeks and the word atom comes from the Greek ‘atomos’ – which means uncuttable.

TULELA: Nice trivia, Sunayana! But since then, we now know that atoms are composed of electrons, protons and neutrons arranged in a particular way.

SUNAYANA: So how did we get from there to our understanding today? NNICK, can you give us a quick history of the structure of the atom?

NNICK: The history of ideas about atoms. The most sensible, mature and adult way to discuss the history of ideas about atoms is through the medium of song.

SONG
Mr John Dalton imagined that atoms
Were miniature spheres that you cannot divide
And then JJ Thomson, who probably liked snacking
Described them as a plum pudding with electrons inside

Rutherford, who was Ernest, suggested a nucleus
Which no one had ever considered before
And around that were shells filled with orbiting electrons
According to that fascinating fellow Niels Bohr

Experiments suggested the existence of protons
Which contribute to the nucleus in a positive way
Add to those the neutrons discovered by Chadwick
And that's the atomic model which we still use today, OK!

SUNAYANA: Thanks, NNICK! Lots to unpack there but sounds like there are some key moments in this history of the atom that we should explore a little. And each one has progressed our understanding. First up, JJ Thomson. From his experiments, he concluded that atoms weren’t solid spheres and he proposed that they looked more like a plum pudding.

TULELA: Who even eats plum pudding these days?

SUNAYANA: Sounds like the kind of dessert they’d have had in 1904 when JJ Thomson came up with the idea. His plum pudding model could be thought of as a positively charged dough spread out evenly in which negatively charged electrons…

TULELA: …the plums…

SUNAYANA: …were embedded. Quite simple, but an advance from the solid spheres model.

TULELA: Anyway, JJ Thomson’s plum pudding model of the atom didn’t last very long because only about a decade later, along comes Ernest Rutherford who tested Thomson’s theory and proved that the plum pudding was way past its sell-by date. And he did this by showing that the positive charge in the atom wasn’t spread out evenly and was in fact concentrated in the centre – the nucleus – where most of the mass of the atom is. And his evidence came from firing positively charged alpha-particles at a very thin sheet of gold foil.

SUNAYANA: Which I shall now demonstrate in the Bitesize studio purely by the magic of sound effects! If Thomson’s plum pudding model was correct then when I fire some alpha particles at the gold foil…

TULELA: Whoa! Careful with that sound effect, Sunayana!

SUNAYANA: Because the positive charges in the gold atoms were thought to be evenly spread out, all the alpha-particle bullets would simply pass straight through – or deflected just a tiny amount if they travelled close to an electron in the plum pudding.

But what they found is that although, yes, most of the alpha particle bullets did indeed pass straight through the foil undeflected, that a few alpha particles were deflected by extreme angles or even reflected backwards as if ricocheting from something.

TULELA: Whoa! Be careful!

SUNAYANA: And this could not have happened with the Thomson plum pudding model.

TULELA: Nice shooting, Sunayana. So, from this experiment, the new model of the atom was now one of mostly empty space where a positively charged mass or nucleus is concentrated at the centre and around this are the electrons. End of story?

SUNAYANA: Not quite yet! Because Rutherford’s model only answered some questions but not all. It didn’t tell us anything more about the electrons. To resolve those questions, we had to wait until Niels Bohr. We had to wait ‘til he proposed a new development of the previous model of the atom. In this, the electrons orbit in particular shells – or energy levels to give them their correct name – which are precisely fixed distance from the nucleus. Again, his experimental observations agreed with his theorical calculations, updating the science and our ideas.

TULELA: So what does that mean, orbiting electrons in shells of a precise distance?

SUNAYANA: I like to think of them as if I were a gymnast twirling a baton over my head and I could choose a different length baton. The electrons are in the ends of the baton spinning around as I dance. They can’t get any closer or further unless I change the baton size – which is like being in a different shell.

TULELA: Baton twirling and alpha particle sharp-shooter – you’d be so talented.

SUNAYANA: Thanks! But we’re not finished yet – because even Niels Bohr’s model needed refining and later experiments from Rutherford again led to the idea that the positively charged nucleus in the atom could be subdivided into a whole number of smaller particles called protons, with each proton having the same amount of positive charge.

TULELA: The end?

SUNAYANA: Not quite – because finally about 20 years after Rutherford’s nuclear model, in 1932 James Chadwick put the final (for the moment) missing pieces into our model of the atom when he proved the existence of neutrons – chargeless particles, also within the atom’s nucleus.

TULELA: And that is the model we use to visualise the atom today. A nucleus of protons and neutrons, with orbiting electrons at specific distances from the nucleus.

SUNAYANA: And if you decide to study chemistry or physics at a higher level, you’ll see how even that model becomes more exciting and extraordinary.

TULELA: And an exciting and extraordinary career in science awaits everyone – every nationality, every gender, every background.

SUNAYANA: I couldn’t agree more.

SUNAYANA: Time for a quick interactive quiz. Three questions, 5 seconds each – here goes…

TULELA: Question 1. Who came up with the plum pudding model of the atom?

SUNAYANA: Answer - JJ Thomson.

TULELA: Question 2. Who showed that this plum pudding wasn’t correct and what was the experiment that proved this?

SUNAYANA: It was Ernest Rutherford who fired alpha particles at gold foil and updated the atom with his nuclear model.

TULELA: And Question 3. How did Niels Bohr’s model update the nuclear model further?

SUNAYANA: He brought in the idea of electrons orbiting the nucleus in energy shells.

TULELA: OK, Sunayana, quick summary?

SUNAYANA: Sure thing.

TULELA: Let’s go. From the ancient Greeks until about 200 years ago, the atom was thought of as tiny solid spheres.

SUNAYANA: Then JJ Thomson comes up with his plum pudding model.

TULELA: Rutherford fires alpha particles at gold foil and shows JJ Thomson was wrong. His nuclear model is one with a positive nucleus.

SUNAYANA: Bohr’s orbiting electron shells helps modify Rutherford’s model.

TULELA: Protons are discovered by Rutherford. Neutrons are discovered by Chadwick and the current model of the atom is in place.

SUNAYANA: And all these developments are a really good example of how science progresses though theory, experiment and evidence.

TULELA: And now I’m hungry. Plum pudding, anyone?

SUNAYANA: In episode three of this series, we’ll be looking at the structure of the atom in more detail its size – its parts, charge and its mass.

I’m Dr Sunayana Bhargava.

TULELA: And I’m Tulela Pea.

SUNAYANA: To hear more, search ‘Bitesize chemistry’ on 91�ȱ� Sounds.

TULELA: Say bye, Sunayana.

SUNAYANA: Bye Sunayana.

TULELA: Thanks for listening.