Maths
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Responding to change (a2 only)
Infection and response
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Organisms respond to changes in their internal and external environments (a-level only)
Biological molecules
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Substance exchange
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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
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Chemistry
12 Dec 2025
216
6 pages
evie @e777
Chemistry might seem complicated, but it's actually about understanding the building blocks that make up everything around you.... Show more
Welcome to the fascinating world of general chemistry! This is your foundation for understanding how matter behaves and interacts. Think of chemistry as the science that explains why things happen - from why your food cooks to how your body digests it.
You'll be exploring atoms, reactions, and the patterns that govern everything in the universe. Don't worry if it seems overwhelming at first - chemistry follows logical rules that you can master with practice.
Remember Chemistry is everywhere in your daily life, so the concepts you learn will help you understand the world around you better.
Every single thing you can touch is made of atoms - they're like the LEGO blocks of the universe! An element is simply a substance made from just one type of atom, like pure gold or oxygen.
Atoms contain three key particles that you need to know. Protons carry a positive charge and live in the nucleus (the centre), along with neutrons which have no charge. Electrons zoom around the outside in shells and have a negative charge.
Here's the clever bit protons and neutrons are much heavier than electrons. That's why most of an atom's mass comes from its nucleus, even though electrons take up most of the space!
Top tip Remember that atoms are mostly empty space - if an atom were the size of a football stadium, the nucleus would be like a marble in the centre!
The reactivity series is basically a league table showing which metals are the most aggressive! Potassium sits at the top as the most reactive (it literally explodes in water), while platinum chills at the bottom, barely reacting with anything.
This isn't just random information - it's incredibly useful for predicting what will happen in reactions. Metals above carbon in the series need electrolysis to extract them from their ores because they're too reactive for simple heating.
Meanwhile, metals below carbon can be extracted by heating with carbon. The really unreactive ones below hydrogen won't even fizz when you add acid to them!
Exam hack Learn the phrase "Please Stop Calling Me A Careless Zebra, Instead Try Learning How Copper Saves Gold Permanently" to remember the order!
Ions are atoms that have gained or lost electrons, giving them an electric charge. Think of them as atoms that have become either greedy (negative ions) or generous (positive ions) with their electrons!
Positive ions include everyday elements like sodium $Na^+$ and calcium $Ca^{2+}$. Notice how some have different charges - this tells you how many electrons they've lost. The higher the number, the more electrons have gone walkabout.
Negative ions like chloride $Cl^-$ and sulfate $SO_4^{2-}$ have grabbed extra electrons. Some are single atoms, whilst others like carbonate $CO_3^{2-}$ are groups of atoms working together.
Memory trick Positive ions are called "cat-ions" because they're attracted to the negative cathode (think of cats being attracted to something!).
The pH scale is like a mood meter for chemicals - it tells you whether something is acidic, neutral, or alkaline. Universal indicator is your detective tool that changes colour to reveal a substance's true chemical personality!
Acids have a pH below 7 and include things like lemon juice and vinegar. Alkalis score above 7 on the pH scale - think soap and bleach. Right in the middle at pH 7 sits pure water, being perfectly neutral and diplomatic.
Weak acids and weak alkalis hover closer to 7, whilst the strong ones live at the extreme ends. Battery acid is around pH 1, whilst household bleach reaches pH 12-13.
Real-world connection Your stomach acid has a pH of about 1.5 - acidic enough to dissolve metal, but your body handles it perfectly!
Neutralisation reactions happen when acids meet their opposite - it's like a chemical peace treaty! These reactions follow predictable patterns that make chemistry much easier once you spot them.
When acids react with alkalis, you get salt plus water. It's that simple! Add a metal to an acid and you'll produce salt plus hydrogen gas. Carbonates are the most dramatic - they fizz and bubble, releasing carbon dioxide.
The key word here is "neutralisation" because the acid and alkali cancel each other out. Think of it like hot and cold water mixing to become lukewarm - the extreme properties balance out.
Lab safety note These reactions can be vigorous, especially with reactive metals, so always follow safety procedures when experimenting!
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.
1
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Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Explore the properties, reactions, and pH scale of acids, bases, and alkalis. This summary covers key concepts such as neutralization, indicators, and examples of common acids and bases, making it essential for Year 8 chemistry students.
ChemistryExplore the fundamental concepts of acids and alkalis in chemistry. This summary covers definitions, key properties, common examples, and testing methods including litmus paper and pH indicators. Ideal for AQA Chemistry students preparing for exams, this resource provides essential insights into neutralization reactions and the role of acids and bases in various chemical contexts.
ChemistryExplore the properties, reactions, and naming conventions of esters and carboxylic acids in this GCSE Chemistry summary. Understand the role of functional groups, acid-base reactions, and the process of esterification. Ideal for AQA Chemical Analysis preparation.
ChemistryApp 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
evie
@e777
Chemistry might seem complicated, but it's actually about understanding the building blocks that make up everything around you. From the atoms in your phone to the reactions happening when you brush your teeth, chemistry explains how our world works at... Show more
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Welcome to the fascinating world of general chemistry! This is your foundation for understanding how matter behaves and interacts. Think of chemistry as the science that explains why things happen - from why your food cooks to how your body digests it.
You'll be exploring atoms, reactions, and the patterns that govern everything in the universe. Don't worry if it seems overwhelming at first - chemistry follows logical rules that you can master with practice.
Remember: Chemistry is everywhere in your daily life, so the concepts you learn will help you understand the world around you better.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Every single thing you can touch is made of atoms - they're like the LEGO blocks of the universe! An element is simply a substance made from just one type of atom, like pure gold or oxygen.
Atoms contain three key particles that you need to know. Protons carry a positive charge and live in the nucleus (the centre), along with neutrons which have no charge. Electrons zoom around the outside in shells and have a negative charge.
Here's the clever bit: protons and neutrons are much heavier than electrons. That's why most of an atom's mass comes from its nucleus, even though electrons take up most of the space!
Top tip: Remember that atoms are mostly empty space - if an atom were the size of a football stadium, the nucleus would be like a marble in the centre!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
The reactivity series is basically a league table showing which metals are the most aggressive! Potassium sits at the top as the most reactive (it literally explodes in water), while platinum chills at the bottom, barely reacting with anything.
This isn't just random information - it's incredibly useful for predicting what will happen in reactions. Metals above carbon in the series need electrolysis to extract them from their ores because they're too reactive for simple heating.
Meanwhile, metals below carbon can be extracted by heating with carbon. The really unreactive ones below hydrogen won't even fizz when you add acid to them!
Exam hack: Learn the phrase "Please Stop Calling Me A Careless Zebra, Instead Try Learning How Copper Saves Gold Permanently" to remember the order!
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Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Ions are atoms that have gained or lost electrons, giving them an electric charge. Think of them as atoms that have become either greedy (negative ions) or generous (positive ions) with their electrons!
Positive ions include everyday elements like sodium $Na^+$ and calcium $Ca^{2+}$. Notice how some have different charges - this tells you how many electrons they've lost. The higher the number, the more electrons have gone walkabout.
Negative ions like chloride $Cl^-$ and sulfate $SO_4^{2-}$ have grabbed extra electrons. Some are single atoms, whilst others like carbonate $CO_3^{2-}$ are groups of atoms working together.
Memory trick: Positive ions are called "cat-ions" because they're attracted to the negative cathode (think of cats being attracted to something!).
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
The pH scale is like a mood meter for chemicals - it tells you whether something is acidic, neutral, or alkaline. Universal indicator is your detective tool that changes colour to reveal a substance's true chemical personality!
Acids have a pH below 7 and include things like lemon juice and vinegar. Alkalis score above 7 on the pH scale - think soap and bleach. Right in the middle at pH 7 sits pure water, being perfectly neutral and diplomatic.
Weak acids and weak alkalis hover closer to 7, whilst the strong ones live at the extreme ends. Battery acid is around pH 1, whilst household bleach reaches pH 12-13.
Real-world connection: Your stomach acid has a pH of about 1.5 - acidic enough to dissolve metal, but your body handles it perfectly!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Neutralisation reactions happen when acids meet their opposite - it's like a chemical peace treaty! These reactions follow predictable patterns that make chemistry much easier once you spot them.
When acids react with alkalis, you get salt plus water. It's that simple! Add a metal to an acid and you'll produce salt plus hydrogen gas. Carbonates are the most dramatic - they fizz and bubble, releasing carbon dioxide.
The key word here is "neutralisation" because the acid and alkali cancel each other out. Think of it like hot and cold water mixing to become lukewarm - the extreme properties balance out.
Lab safety note: These reactions can be vigorous, especially with reactive metals, so always follow safety procedures when experimenting!
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.
1
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Explore the properties, reactions, and pH scale of acids, bases, and alkalis. This summary covers key concepts such as neutralization, indicators, and examples of common acids and bases, making it essential for Year 8 chemistry students.
ChemistryExplore the fundamental concepts of acids and alkalis in chemistry. This summary covers definitions, key properties, common examples, and testing methods including litmus paper and pH indicators. Ideal for AQA Chemistry students preparing for exams, this resource provides essential insights into neutralization reactions and the role of acids and bases in various chemical contexts.
ChemistryExplore the properties, reactions, and naming conventions of esters and carboxylic acids in this GCSE Chemistry summary. Understand the role of functional groups, acid-base reactions, and the process of esterification. Ideal for AQA Chemical Analysis preparation.
ChemistryApp 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
Sociology