Maths
Chemistry
Biology
English Language
History
Responding to change (a2 only)
Infection and response
Homeostasis and response
Energy transfers (a2 only)
Cell biology
Organisms respond to changes in their internal and external environments (a-level only)
Biological molecules
Organisation
Substance exchange
Bioenergetics
Genetic information & variation
Inheritance, variation and evolution
Genetics & ecosystems (a2 only)
Ecology
Cells
Show all topics
Britain & the wider world: 1745 -1901
1l the quest for political stability: germany, 1871-1991
The cold war
Inter-war germany
Medieval period: 1066 -1509
2d religious conflict and the church in england, c1529-c1570
2o democracy and nazism: germany, 1918-1945
1f industrialisation and the people: britain, c1783-1885
1c the tudors: england, 1485-1603
2m wars and welfare: britain in transition, 1906-1957
World war two & the holocaust
2n revolution and dictatorship: russia, 1917-1953
2s the making of modern britain, 1951-2007
World war one
Britain: 1509 -1745
Show all topics
128
•
10 Dec 2025
•
Chloe Parkes
@chloeparkes
Chemistry might seem complex, but it's actually about understanding the... Show more
Every single thing you can touch is made of atoms - they're literally the smallest bits of an element that can exist on their own. Think of them as nature's Lego blocks that build everything from your phone to your morning toast.
When two or more different elements chemically stick together, you get a compound. These are held together so tightly that you need a proper chemical reaction to separate them again. The brilliant thing is that compounds follow the law of conservation of mass - whatever mass goes into a reaction must equal what comes out.
Mixtures are completely different though. Here, elements just hang out together without forming chemical bonds, so you can separate them using physical methods like filtering or heating.
💡 Quick tip: Remember compounds = chemically bonded (hard to separate), mixtures = just mixed together (easy to separate)!
The atomic model has evolved loads over time. Scientists went from thinking atoms were tiny solid spheres to discovering they're mostly empty space with electrons whizzing around a nucleus. Each breakthrough - from Thomson's "plum pudding" to Rutherford's nuclear model - helped us understand atoms better.
Protons have a +1 charge, neutrons are neutral (0 charge), and electrons have a -1 charge. Protons and neutrons both have a mass of 1, whilst electrons are so tiny their mass is basically negligible.
Isotopes are atoms of the same element with different numbers of neutrons. They're like identical twins who weigh different amounts - same chemical properties but different physical ones. Some isotopes can be radioactive, which makes them useful in medicine and industry.
Electrons live in shells around the nucleus. The first shell holds up to 2 electrons, and all the others can hold up to 8. This arrangement determines how atoms behave and what they'll bond with.
💡 Remember: The electronic structure tells you everything about how an atom will react!
The periodic table arranges elements by atomic number, and there's a brilliant pattern - elements in the same group (column) have the same number of electrons in their outer shell. That's why elements in the same group behave similarly.
Group 1 alkali metals are the show-offs of the periodic table - they've only got one electron in their outer shell and they're desperate to get rid of it. This makes them incredibly reactive, and they get more reactive as you go down the group because the outer electron gets further from the nucleus.
Group 7 halogens are the opposite - they've got seven electrons in their outer shell and really want one more to complete it. They exist as diatomic molecules (pairs) and get less reactive as you go down the group.
Group 0 noble gases are the chilled-out ones with full outer shells. They're basically unreactive because they're already stable and don't need to gain or lose electrons.
💡 Pattern spotting: Reactivity in Group 1 increases down the group, but in Group 7 it decreases!
Ionic bonding happens when metals meet non-metals. The metal loses electrons to become positively charged, the non-metal gains them to become negatively charged, and then they stick together through electrostatic attraction.
Covalent bonding is all about sharing - non-metal atoms share pairs of electrons to fill their outer shells. It's like best mates sharing everything because they both benefit from the arrangement.
Metallic bonding creates a "sea" of delocalised electrons that can move freely through the metal structure. This is why metals conduct electricity and heat so well - those free electrons can carry energy around.
The type of bonding completely determines a material's properties. Small covalent molecules have weak forces between them, so they have low melting points and don't conduct electricity.
💡 Key insight: The bonding type predicts the properties - learn the bonding, predict the behaviour!
Ionic compounds form regular structures with strong electrostatic forces, giving them high melting points. They only conduct electricity when molten or dissolved because the ions need to be free to move. Giant covalent structures like diamond have incredibly high melting points because breaking them means snapping strong covalent bonds.
Diamond and graphite are both pure carbon but couldn't be more different. Diamond has each carbon forming four covalent bonds in a 3D network, making it incredibly hard. Graphite has each carbon forming three bonds in layers, with delocalised electrons that let it conduct electricity.
Graphene is basically a single layer of graphite - it's like the ultimate 2D material. Fullerenes are hollow carbon molecules that can form tubes (carbon nanotubes) or ball shapes, opening up amazing possibilities in nanotechnology.
In pure metals, atoms arrange in neat layers that can slide over each other, making metals malleable. Alloys disrupt these layers with different-sized atoms, making them harder and stronger.
💡 Cool fact: Carbon nanotubes are stronger than steel but lighter than plastic - they're revolutionising materials science!
Nanoparticles are tiny but mighty - they're used in everything from suncream to medicine. Their huge surface area makes them brilliant catalysts and UV blockers, but we're still learning about potential health and environmental effects. The key is their size gives them properties that bulk materials don't have.
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
You can download the app from Google Play Store and Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
App Store
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
Chloe Parkes
@chloeparkes
Chemistry might seem complex, but it's actually about understanding the building blocks of everything around you. This guide covers the fundamentals of atoms, how they bond together, and why different materials have such different properties.
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Every single thing you can touch is made of atoms - they're literally the smallest bits of an element that can exist on their own. Think of them as nature's Lego blocks that build everything from your phone to your morning toast.
When two or more different elements chemically stick together, you get a compound. These are held together so tightly that you need a proper chemical reaction to separate them again. The brilliant thing is that compounds follow the law of conservation of mass - whatever mass goes into a reaction must equal what comes out.
Mixtures are completely different though. Here, elements just hang out together without forming chemical bonds, so you can separate them using physical methods like filtering or heating.
💡 Quick tip: Remember compounds = chemically bonded (hard to separate), mixtures = just mixed together (easy to separate)!
The atomic model has evolved loads over time. Scientists went from thinking atoms were tiny solid spheres to discovering they're mostly empty space with electrons whizzing around a nucleus. Each breakthrough - from Thomson's "plum pudding" to Rutherford's nuclear model - helped us understand atoms better.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Protons have a +1 charge, neutrons are neutral (0 charge), and electrons have a -1 charge. Protons and neutrons both have a mass of 1, whilst electrons are so tiny their mass is basically negligible.
Isotopes are atoms of the same element with different numbers of neutrons. They're like identical twins who weigh different amounts - same chemical properties but different physical ones. Some isotopes can be radioactive, which makes them useful in medicine and industry.
Electrons live in shells around the nucleus. The first shell holds up to 2 electrons, and all the others can hold up to 8. This arrangement determines how atoms behave and what they'll bond with.
💡 Remember: The electronic structure tells you everything about how an atom will react!
The periodic table arranges elements by atomic number, and there's a brilliant pattern - elements in the same group (column) have the same number of electrons in their outer shell. That's why elements in the same group behave similarly.
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Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Group 1 alkali metals are the show-offs of the periodic table - they've only got one electron in their outer shell and they're desperate to get rid of it. This makes them incredibly reactive, and they get more reactive as you go down the group because the outer electron gets further from the nucleus.
Group 7 halogens are the opposite - they've got seven electrons in their outer shell and really want one more to complete it. They exist as diatomic molecules (pairs) and get less reactive as you go down the group.
Group 0 noble gases are the chilled-out ones with full outer shells. They're basically unreactive because they're already stable and don't need to gain or lose electrons.
💡 Pattern spotting: Reactivity in Group 1 increases down the group, but in Group 7 it decreases!
Ionic bonding happens when metals meet non-metals. The metal loses electrons to become positively charged, the non-metal gains them to become negatively charged, and then they stick together through electrostatic attraction.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Covalent bonding is all about sharing - non-metal atoms share pairs of electrons to fill their outer shells. It's like best mates sharing everything because they both benefit from the arrangement.
Metallic bonding creates a "sea" of delocalised electrons that can move freely through the metal structure. This is why metals conduct electricity and heat so well - those free electrons can carry energy around.
The type of bonding completely determines a material's properties. Small covalent molecules have weak forces between them, so they have low melting points and don't conduct electricity.
💡 Key insight: The bonding type predicts the properties - learn the bonding, predict the behaviour!
Ionic compounds form regular structures with strong electrostatic forces, giving them high melting points. They only conduct electricity when molten or dissolved because the ions need to be free to move. Giant covalent structures like diamond have incredibly high melting points because breaking them means snapping strong covalent bonds.
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Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Diamond and graphite are both pure carbon but couldn't be more different. Diamond has each carbon forming four covalent bonds in a 3D network, making it incredibly hard. Graphite has each carbon forming three bonds in layers, with delocalised electrons that let it conduct electricity.
Graphene is basically a single layer of graphite - it's like the ultimate 2D material. Fullerenes are hollow carbon molecules that can form tubes (carbon nanotubes) or ball shapes, opening up amazing possibilities in nanotechnology.
In pure metals, atoms arrange in neat layers that can slide over each other, making metals malleable. Alloys disrupt these layers with different-sized atoms, making them harder and stronger.
💡 Cool fact: Carbon nanotubes are stronger than steel but lighter than plastic - they're revolutionising materials science!
Nanoparticles are tiny but mighty - they're used in everything from suncream to medicine. Their huge surface area makes them brilliant catalysts and UV blockers, but we're still learning about potential health and environmental effects. The key is their size gives them properties that bulk materials don't have.
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
You can download the app from Google Play Store and Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
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The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
Sociology