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5 Dec 2025
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GCSE AQA Chemistry Unit 9: The Atmosphere Notes
Dae ๐๐ชฉ
@d_h708
1 / 3
Earth's Atmospheric Evolution
Your atmosphere today is basically four-fifths nitrogen and one-fifth oxygen, with tiny amounts of other gases like carbon dioxide. This perfect recipe for life took billions of years to develop, and it's been stable for about 200 million years.
Picture Earth 4.6 billion years ago โ it was nothing like the planet you know. Massive volcanic activity spewed gases everywhere, creating an atmosphere more like Mars or Venus today. The early atmosphere was mainly carbon dioxide with virtually no oxygen, making it completely deadly to any life forms.
Photosynthesis changed everything. About 2.7 billion years ago, algae started the process that would transform our planet: 6COโ + 6HโO โ CโHโโOโ + 6Oโ. This simple equation represents the most important chemical reaction in Earth's history โ turning carbon dioxide and water into glucose and oxygen.
Key Insight: The oxygen you're breathing right now was created by ancient algae and plants over billions of years through photosynthesis.
The Greenhouse Effect and Climate Change
Greenhouse gases like water vapour, carbon dioxide, and methane act like a blanket around Earth. They let sunlight in but trap heat trying to escape, keeping our planet warm enough for life โ without this natural process, Earth would be a frozen wasteland.
The problem isn't the greenhouse effect itself, but how we're making it stronger. Burning fossil fuels pumps extra carbon dioxide into the atmosphere, whilst increased farming adds more methane from livestock and decomposing waste. The evidence is clear: COโ levels have shot up alongside fossil fuel use over the past century.
Global climate change brings serious consequences you'll likely face in your lifetime. Rising sea levels threaten coastal areas, extreme weather becomes more common, and changing rainfall patterns affect food production. Wildlife struggles to adapt, and some species may disappear entirely.
Your carbon footprint measures all the greenhouse gases produced by your lifestyle choices. You can reduce it through renewable energy, carbon capture technology, or even planting trees, but progress faces real challenges like scientific disagreements, lifestyle resistance, and economic costs.
Key Insight: Climate change isn't just an environmental issue โ it affects everything from the food you eat to where you can safely live.
Fuel Combustion and Air Pollution
Every time you burn fuel โ whether in cars, power plants, or heating systems โ you're creating atmospheric pollutants that affect both human health and the environment. Understanding combustion helps explain why air quality matters so much.
Complete combustion happens when there's plenty of oxygen available. The fuel burns cleanly, producing just carbon dioxide and water vapour whilst releasing maximum energy. However, incomplete combustion occurs with limited oxygen, creating dangerous carbon monoxide โ a colourless, odourless gas that reduces your blood's ability to carry oxygen.
Fuels containing sulfur impurities produce sulfur dioxide when burned, whilst the extreme heat creates nitrogen oxides from atmospheric gases. These pollutants cause breathing problems and create acid rain that damages buildings and plant life.
Particulates โ tiny solid particles from incomplete combustion โ create two major problems. They cause serious lung damage when inhaled and contribute to global dimming by blocking sunlight from reaching Earth's surface, affecting weather patterns worldwide.
Key Insight: The type of combustion matters enormously โ complete combustion produces more energy and far fewer harmful pollutants than incomplete combustion.
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Samantha Klich
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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 itโs 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 didnโt even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as Iโm 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 ๐๐๐ฒ๐ค๐โจ๐๐ฎ
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 itโs 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 didnโt even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as Iโm 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 ๐๐๐ฒ๐ค๐โจ๐๐ฎ
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
GCSE AQA Chemistry Unit 9: The Atmosphere Notes
Dae ๐๐ชฉ
@d_h708
Ever wondered how Earth went from a toxic, unbreathable planet to the life-supporting world we know today? The atmosphere's journey from volcanic chaos to the perfect balance of gases is one of the most incredible transformations in Earth's history, and... Show more
Earth's Atmospheric Evolution
Your atmosphere today is basically four-fifths nitrogen and one-fifth oxygen, with tiny amounts of other gases like carbon dioxide. This perfect recipe for life took billions of years to develop, and it's been stable for about 200 million years.
Picture Earth 4.6 billion years ago โ it was nothing like the planet you know. Massive volcanic activity spewed gases everywhere, creating an atmosphere more like Mars or Venus today. The early atmosphere was mainly carbon dioxide with virtually no oxygen, making it completely deadly to any life forms.
Photosynthesis changed everything. About 2.7 billion years ago, algae started the process that would transform our planet: 6COโ + 6HโO โ CโHโโOโ + 6Oโ. This simple equation represents the most important chemical reaction in Earth's history โ turning carbon dioxide and water into glucose and oxygen.
Key Insight: The oxygen you're breathing right now was created by ancient algae and plants over billions of years through photosynthesis.
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
The Greenhouse Effect and Climate Change
Greenhouse gases like water vapour, carbon dioxide, and methane act like a blanket around Earth. They let sunlight in but trap heat trying to escape, keeping our planet warm enough for life โ without this natural process, Earth would be a frozen wasteland.
The problem isn't the greenhouse effect itself, but how we're making it stronger. Burning fossil fuels pumps extra carbon dioxide into the atmosphere, whilst increased farming adds more methane from livestock and decomposing waste. The evidence is clear: COโ levels have shot up alongside fossil fuel use over the past century.
Global climate change brings serious consequences you'll likely face in your lifetime. Rising sea levels threaten coastal areas, extreme weather becomes more common, and changing rainfall patterns affect food production. Wildlife struggles to adapt, and some species may disappear entirely.
Your carbon footprint measures all the greenhouse gases produced by your lifestyle choices. You can reduce it through renewable energy, carbon capture technology, or even planting trees, but progress faces real challenges like scientific disagreements, lifestyle resistance, and economic costs.
Key Insight: Climate change isn't just an environmental issue โ it affects everything from the food you eat to where you can safely live.
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Fuel Combustion and Air Pollution
Every time you burn fuel โ whether in cars, power plants, or heating systems โ you're creating atmospheric pollutants that affect both human health and the environment. Understanding combustion helps explain why air quality matters so much.
Complete combustion happens when there's plenty of oxygen available. The fuel burns cleanly, producing just carbon dioxide and water vapour whilst releasing maximum energy. However, incomplete combustion occurs with limited oxygen, creating dangerous carbon monoxide โ a colourless, odourless gas that reduces your blood's ability to carry oxygen.
Fuels containing sulfur impurities produce sulfur dioxide when burned, whilst the extreme heat creates nitrogen oxides from atmospheric gases. These pollutants cause breathing problems and create acid rain that damages buildings and plant life.
Particulates โ tiny solid particles from incomplete combustion โ create two major problems. They cause serious lung damage when inhaled and contribute to global dimming by blocking sunlight from reaching Earth's surface, affecting weather patterns worldwide.
Key Insight: The type of combustion matters enormously โ complete combustion produces more energy and far fewer harmful pollutants than incomplete combustion.
We thought youโd never ask...
What is the Knowunity AI companion?
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.
Where can I download the Knowunity app?
You can download the app from Google Play Store and Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help โ all at your fingertips.
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Most popular content in Chemistry
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English - inspector calls quotes and analysis
Quotes from every main character
English Literature10
Can't find what you're looking for? Explore other subjects.
Students love us โ and so will you.
4.9/5
App Store
4.8/5
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 itโs 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 didnโt even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as Iโm 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 ๐๐๐ฒ๐ค๐โจ๐๐ฎ
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 itโs 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 didnโt even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as Iโm 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 ๐๐๐ฒ๐ค๐โจ๐๐ฎ
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