Subjects
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
Chemistry
14 Dec 2025
126
2 pages
faiaz @1kfaiaz
Understanding the amount of substance is crucial for chemistry calculations and real-world chemical applications. This topic covers everything... Show more
Ever wondered why your calculator shows weird decimal numbers for atomic masses instead of nice whole numbers? That's because atomic masses are actually averages of all the isotopes of an element, weighted by how common each one is.
Isotopes are atoms with the same number of protons but different numbers of neutrons. They behave identically in chemical reactions (same electrons), but have different physical properties because of their different masses. Scientists use mass spectrometers to work out how much of each isotope exists - the machine separates ions by mass and counts them.
When metals react with acids, they follow predictable patterns that you'll need to memorise. Metal + acid always gives you a salt plus hydrogen gas. Add water or carbon dioxide depending on whether you started with an oxide, hydroxide, or carbonate.
Quick tip Remember that cations are positive ions and anions are negative - think "cats are pawsitive"!
The mole is chemistry's way of counting ridiculously large numbers of atoms - one mole contains 6.02×10²³ particles (Avogadro's constant). Think of it like buying eggs by the dozen, but for atoms!
Gas volume calculations are surprisingly straightforward one mole of any gas takes up 24 dm³ at room temperature and pressure. For more complex situations, you'll use the ideal gas equation PV = nRT, where each letter represents pressure, volume, moles, gas constant, and temperature respectively.
Solutions and concentration calculations link mass, volume, and molarity. You can find moles by dividing mass by molar mass, or by multiplying concentration by volume. Standard solutions are made by dissolving an exact mass and diluting to an exact volume.
Hydrated salts contain water molecules trapped in their crystal structure (like CuSO₄·5H₂O). When heated, they lose this water and become anhydrous, often changing colour - blue copper sulfate turns white when dehydrated.
Remember Always heat to constant mass when removing water to ensure you've driven off every last bit!
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.
0
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Explore the fundamentals of atomic structure, relative atomic mass, and isotopes in this detailed summary. Understand concepts like average atomic mass, ionization, and the role of mass spectrometry in determining percentage abundance. Ideal for A Level Chemistry students preparing for exams.
ChemistryExplore the fundamentals of atomic structure, including ionization energies, electron configurations, isotopes, and mass spectrometry. This comprehensive summary covers key concepts such as atomic radius, shielding effects, and the historical development of atomic models. Ideal for A-level Chemistry students preparing for exams.
ChemistryExplore the principles and methods of mass spectrometry, including electron impact and electrospray ionisation. Understand how molecular ions are formed, the significance of mass spectra, and how to calculate relative atomic mass. Ideal for AQA A-level chemistry students.
ChemistryC1 Chemistry (Atoms etc)
ChemistryExplore the fundamentals of isotopes, including definitions, calculations of relative atomic mass, and the relationship between protons, neutrons, and mass number. This summary covers key concepts such as relative abundance and atomic structure, essential for mastering Module 2 in Chemistry.
ChemistryExplore the concepts of mass number, atomic number, and isotopes in this detailed summary for A Level Chemistry. Learn how to calculate relative atomic mass, understand the significance of ions, and differentiate between isotopes. This resource includes examples and calculations to enhance your understanding of atomic structure.
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
faiaz
@1kfaiaz
Understanding the amount of substance is crucial for chemistry calculations and real-world chemical applications. This topic covers everything from counting atoms using moles to calculating how efficient chemical reactions are in industry.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Ever wondered why your calculator shows weird decimal numbers for atomic masses instead of nice whole numbers? That's because atomic masses are actually averages of all the isotopes of an element, weighted by how common each one is.
Isotopes are atoms with the same number of protons but different numbers of neutrons. They behave identically in chemical reactions (same electrons), but have different physical properties because of their different masses. Scientists use mass spectrometers to work out how much of each isotope exists - the machine separates ions by mass and counts them.
When metals react with acids, they follow predictable patterns that you'll need to memorise. Metal + acid always gives you a salt plus hydrogen gas. Add water or carbon dioxide depending on whether you started with an oxide, hydroxide, or carbonate.
Quick tip: Remember that cations are positive ions and anions are negative - think "cats are pawsitive"!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
The mole is chemistry's way of counting ridiculously large numbers of atoms - one mole contains 6.02×10²³ particles (Avogadro's constant). Think of it like buying eggs by the dozen, but for atoms!
Gas volume calculations are surprisingly straightforward: one mole of any gas takes up 24 dm³ at room temperature and pressure. For more complex situations, you'll use the ideal gas equation: PV = nRT, where each letter represents pressure, volume, moles, gas constant, and temperature respectively.
Solutions and concentration calculations link mass, volume, and molarity. You can find moles by dividing mass by molar mass, or by multiplying concentration by volume. Standard solutions are made by dissolving an exact mass and diluting to an exact volume.
Hydrated salts contain water molecules trapped in their crystal structure (like CuSO₄·5H₂O). When heated, they lose this water and become anhydrous, often changing colour - blue copper sulfate turns white when dehydrated.
Remember: Always heat to constant mass when removing water to ensure you've driven off every last bit!
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.
0
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Explore the fundamentals of atomic structure, relative atomic mass, and isotopes in this detailed summary. Understand concepts like average atomic mass, ionization, and the role of mass spectrometry in determining percentage abundance. Ideal for A Level Chemistry students preparing for exams.
ChemistryExplore the fundamentals of atomic structure, including ionization energies, electron configurations, isotopes, and mass spectrometry. This comprehensive summary covers key concepts such as atomic radius, shielding effects, and the historical development of atomic models. Ideal for A-level Chemistry students preparing for exams.
ChemistryExplore the principles and methods of mass spectrometry, including electron impact and electrospray ionisation. Understand how molecular ions are formed, the significance of mass spectra, and how to calculate relative atomic mass. Ideal for AQA A-level chemistry students.
ChemistryC1 Chemistry (Atoms etc)
ChemistryExplore the fundamentals of isotopes, including definitions, calculations of relative atomic mass, and the relationship between protons, neutrons, and mass number. This summary covers key concepts such as relative abundance and atomic structure, essential for mastering Module 2 in Chemistry.
ChemistryExplore the concepts of mass number, atomic number, and isotopes in this detailed summary for A Level Chemistry. Learn how to calculate relative atomic mass, understand the significance of ions, and differentiate between isotopes. This resource includes examples and calculations to enhance your understanding of atomic structure.
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