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
0
0
izzy
02/12/2025
Chemistry
Atmosphere
74
•
2 Dec 2025
•
izzy
@ib2008
Earth's atmosphere has dramatically transformed over billions of years, evolving... Show more
Earth's atmosphere tells an incredible 4.6 billion year story that's still unfolding today. When our planet first formed, volcanic activity released massive amounts of water vapour and carbon dioxide into the air, creating conditions nothing like what we experience now.
As Earth cooled down, something amazing happened—water vapour condensed and fell as rain, eventually forming our oceans. This was a game-changer because carbon dioxide could now dissolve into these new bodies of water, reducing its concentration in the atmosphere.
Nitrogen also escaped from volcanoes, but since it's quite unreactive, it just kept building up in the atmosphere over time. The early atmosphere probably resembled what we see on Venus and Mars today—mostly carbon dioxide with little to no oxygen.
The real transformation began with photosynthesis. Plants and algae started producing oxygen as they made their own food, completely changing the atmospheric composition. This oxygen boost was so significant that animals could finally start evolving around 600 million years ago.
Key Insight: Without photosynthesis, Earth's atmosphere would still be toxic to most life forms we know today!
You might wonder where all that early carbon dioxide went—the answer lies in fossil fuels and sedimentary rocks. Over millions of years, ancient plants, algae, and plankton absorbed carbon dioxide through photosynthesis, then got buried and compressed into coal, oil, and natural gas.
Sedimentary rocks like limestone also locked away carbon dioxide. The gas dissolved in early oceans, formed carbonate ions, and reacted with metal ions to create insoluble carbonates that eventually became rock layers.
Today's greenhouse gases—including carbon dioxide, methane, and water vapour—actually serve a vital purpose. They keep Earth warm enough for life to exist by absorbing and re-emitting radiation from the sun.
Here's how the greenhouse effect works: energy from the sun reaches Earth, some gets reflected back to space, but the rest warms our surface. The warm surface then emits radiation, which greenhouse gases absorb and re-emit in all directions, keeping our planet cosy.
Remember: The greenhouse effect isn't inherently bad—without it, Earth would be a frozen wasteland!
Human activities have dramatically increased greenhouse gas levels, particularly carbon dioxide from burning fossil fuels for transport, electricity, and manufacturing. While CO₂ gets most attention, methane is actually much more powerful—it's released through cattle farming, mining, and waste decomposition.
Scientists have clearly linked rising carbon dioxide levels to increasing global temperatures. The IPCC (Intergovernmental Panel on Climate Change) bases these conclusions on massive amounts of research from around the world.
Climate change impacts include more heatwaves, droughts in some areas, increased rainfall in others, and fewer cold periods. Remember: weather describes short-term conditions, while climate refers to long-term patterns over about 30 years.
Your carbon footprint measures all greenhouse gas emissions from your lifestyle—transport, food, energy use, and products you buy. You can reduce it by walking instead of driving, turning off lights, and making conscious choices about consumption.
Atmospheric pollutants from burning fossil fuels include carbon monoxide (toxic and colourless), unburnt hydrocarbons, and soot particles. These cause breathing problems and contribute to global warming, showing why cleaner energy sources are essential.
Action Point: Small daily choices like cycling to school or switching off electronics can genuinely reduce your environmental impact!
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.
Quotes from every main character
English LiteratureApp 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
izzy
@ib2008
Earth's atmosphere has dramatically transformed over billions of years, evolving from a toxic mix of volcanic gases to the oxygen-rich air we breathe today. Understanding how our atmosphere developed—and how human activities are now changing it—is crucial for grasping current... Show more
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Earth's atmosphere tells an incredible 4.6 billion year story that's still unfolding today. When our planet first formed, volcanic activity released massive amounts of water vapour and carbon dioxide into the air, creating conditions nothing like what we experience now.
As Earth cooled down, something amazing happened—water vapour condensed and fell as rain, eventually forming our oceans. This was a game-changer because carbon dioxide could now dissolve into these new bodies of water, reducing its concentration in the atmosphere.
Nitrogen also escaped from volcanoes, but since it's quite unreactive, it just kept building up in the atmosphere over time. The early atmosphere probably resembled what we see on Venus and Mars today—mostly carbon dioxide with little to no oxygen.
The real transformation began with photosynthesis. Plants and algae started producing oxygen as they made their own food, completely changing the atmospheric composition. This oxygen boost was so significant that animals could finally start evolving around 600 million years ago.
Key Insight: Without photosynthesis, Earth's atmosphere would still be toxic to most life forms we know today!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
You might wonder where all that early carbon dioxide went—the answer lies in fossil fuels and sedimentary rocks. Over millions of years, ancient plants, algae, and plankton absorbed carbon dioxide through photosynthesis, then got buried and compressed into coal, oil, and natural gas.
Sedimentary rocks like limestone also locked away carbon dioxide. The gas dissolved in early oceans, formed carbonate ions, and reacted with metal ions to create insoluble carbonates that eventually became rock layers.
Today's greenhouse gases—including carbon dioxide, methane, and water vapour—actually serve a vital purpose. They keep Earth warm enough for life to exist by absorbing and re-emitting radiation from the sun.
Here's how the greenhouse effect works: energy from the sun reaches Earth, some gets reflected back to space, but the rest warms our surface. The warm surface then emits radiation, which greenhouse gases absorb and re-emit in all directions, keeping our planet cosy.
Remember: The greenhouse effect isn't inherently bad—without it, Earth would be a frozen wasteland!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Human activities have dramatically increased greenhouse gas levels, particularly carbon dioxide from burning fossil fuels for transport, electricity, and manufacturing. While CO₂ gets most attention, methane is actually much more powerful—it's released through cattle farming, mining, and waste decomposition.
Scientists have clearly linked rising carbon dioxide levels to increasing global temperatures. The IPCC (Intergovernmental Panel on Climate Change) bases these conclusions on massive amounts of research from around the world.
Climate change impacts include more heatwaves, droughts in some areas, increased rainfall in others, and fewer cold periods. Remember: weather describes short-term conditions, while climate refers to long-term patterns over about 30 years.
Your carbon footprint measures all greenhouse gas emissions from your lifestyle—transport, food, energy use, and products you buy. You can reduce it by walking instead of driving, turning off lights, and making conscious choices about consumption.
Atmospheric pollutants from burning fossil fuels include carbon monoxide (toxic and colourless), unburnt hydrocarbons, and soot particles. These cause breathing problems and contribute to global warming, showing why cleaner energy sources are essential.
Action Point: Small daily choices like cycling to school or switching off electronics can genuinely reduce your environmental impact!
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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Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Quotes from every main character
English LiteratureApp 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