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29 Nov 2025
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AQA GCSE Organic Chemistry Unit 7 Notes for Triple Science
Dae ๐๐ชฉ
@d_h708
1 / 6
Crude Oil and Alkanes
Crude oil might look like black gunk, but it's actually ancient treasure formed from tiny sea creatures called plankton that died millions of years ago. This finite resource contains loads of different compounds, mostly hydrocarbons - molecules made entirely of hydrogen and carbon atoms.
The most common hydrocarbons in crude oil are alkanes, which are like the well-behaved cousins of the hydrocarbon family. They only have single bonds between their carbon atoms, making them saturated hydrocarbons. Think methane (CHโ), ethane (CโHโ), propane (CโHโ), and butane (CโHโโ) - they all follow the pattern CโHโโโโ.
Here's something brilliant: as alkane molecules get bigger, they become less volatile (harder to evaporate) and less flammable, but their boiling points and thickness increase. This is why petrol evaporates quickly whilst engine oil doesn't - it's all about molecular size!
Quick Test Tip: Remember that complete combustion of any hydrocarbon always produces just carbon dioxide and water: Hydrocarbon + Oxygen โ COโ + HโO
Alkenes and Their Reactions
Meet the rebels of the hydrocarbon world - alkenes! These molecules contain a carbon-carbon double bond, making them unsaturated and much more reactive than their alkane cousins. Their general formula is CโHโโ, so ethene is CโHโ and propene is CโHโ.
You can easily spot alkenes using the bromine water test - they turn orange bromine water colourless, whilst alkanes don't react at all. When alkenes burn, they often produce smoky flames because they don't combust as cleanly as alkanes.
The real magic happens with addition reactions. That double bond acts like a trap door - it opens up to let other atoms join the molecule. Alkenes can react with hydrogen (making alkanes), water (making alcohols), and halogens like bromine or chlorine. The double bond breaks and becomes a single bond as new atoms attach.
Exam Success: Always remember that in addition reactions, the double bond opens up and atoms add across it - this is how ethene becomes ethanol when it reacts with water!
Polymerisation - Making Giant Molecules
Here's where chemistry gets properly exciting - turning tiny molecules into massive ones! Addition polymerisation takes loads of small alkene molecules (called monomers) and joins them together like a giant molecular chain to create polymers such as poly(ethene) - basically plastic bags and bottles.
During this process, those reactive double bonds in alkenes break open and link up with neighbouring molecules. The brilliant thing is that the repeating unit in the polymer contains exactly the same atoms as the original monomer - nothing gets lost or added.
Condensation polymerisation works differently and creates materials like polyester. Here, two different monomers join together, but they kick out small molecules (usually water) in the process. For example, when ethanediol meets hexanedioic acid, they form a polyester chain and release water molecules.
Memory Trick: Addition = double bonds opening up and joining; Condensation = two different molecules joining and losing water!
Natural Polymers - The Chemistry of Life
Your body is basically a walking chemistry lab filled with amazing natural polymers! Amino acids are like biological building blocks that join together through condensation polymerisation to create proteins. Each amino acid has two functional groups that can link up, and when they do, they release water molecules.
DNA is probably the most important polymer you'll ever encounter - it's made from four different monomers called nucleotides arranged in that famous double helix structure. This incredible molecule stores all the genetic instructions that make you... well, you!
Other natural polymers are everywhere around you. Starch and cellulose are both made from glucose monomers - starch stores energy in plants whilst cellulose gives them structure. It's amazing how the same building block can create completely different materials!
Real-World Connection: Every time you eat bread (starch), wear a cotton shirt (cellulose), or literally just exist (proteins and DNA), you're experiencing the power of natural polymerisation!
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The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
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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
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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
AQA GCSE Organic Chemistry Unit 7 Notes for Triple Science
Dae ๐๐ชฉ
@d_h708
Ever wondered what makes up petrol, plastic bags, and even your own DNA? Welcome to organic chemistry - the fascinating world of carbon-based molecules that form the building blocks of life and many everyday materials. From the crude oil that... Show more
Crude Oil and Alkanes
Crude oil might look like black gunk, but it's actually ancient treasure formed from tiny sea creatures called plankton that died millions of years ago. This finite resource contains loads of different compounds, mostly hydrocarbons - molecules made entirely of hydrogen and carbon atoms.
The most common hydrocarbons in crude oil are alkanes, which are like the well-behaved cousins of the hydrocarbon family. They only have single bonds between their carbon atoms, making them saturated hydrocarbons. Think methane (CHโ), ethane (CโHโ), propane (CโHโ), and butane (CโHโโ) - they all follow the pattern CโHโโโโ.
Here's something brilliant: as alkane molecules get bigger, they become less volatile (harder to evaporate) and less flammable, but their boiling points and thickness increase. This is why petrol evaporates quickly whilst engine oil doesn't - it's all about molecular size!
Quick Test Tip: Remember that complete combustion of any hydrocarbon always produces just carbon dioxide and water: Hydrocarbon + Oxygen โ COโ + HโO
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Improve your grades
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Alkenes and Their Reactions
Meet the rebels of the hydrocarbon world - alkenes! These molecules contain a carbon-carbon double bond, making them unsaturated and much more reactive than their alkane cousins. Their general formula is CโHโโ, so ethene is CโHโ and propene is CโHโ.
You can easily spot alkenes using the bromine water test - they turn orange bromine water colourless, whilst alkanes don't react at all. When alkenes burn, they often produce smoky flames because they don't combust as cleanly as alkanes.
The real magic happens with addition reactions. That double bond acts like a trap door - it opens up to let other atoms join the molecule. Alkenes can react with hydrogen (making alkanes), water (making alcohols), and halogens like bromine or chlorine. The double bond breaks and becomes a single bond as new atoms attach.
Exam Success: Always remember that in addition reactions, the double bond opens up and atoms add across it - this is how ethene becomes ethanol when it reacts with water!
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
Polymerisation - Making Giant Molecules
Here's where chemistry gets properly exciting - turning tiny molecules into massive ones! Addition polymerisation takes loads of small alkene molecules (called monomers) and joins them together like a giant molecular chain to create polymers such as poly(ethene) - basically plastic bags and bottles.
During this process, those reactive double bonds in alkenes break open and link up with neighbouring molecules. The brilliant thing is that the repeating unit in the polymer contains exactly the same atoms as the original monomer - nothing gets lost or added.
Condensation polymerisation works differently and creates materials like polyester. Here, two different monomers join together, but they kick out small molecules (usually water) in the process. For example, when ethanediol meets hexanedioic acid, they form a polyester chain and release water molecules.
Memory Trick: Addition = double bonds opening up and joining; Condensation = two different molecules joining and losing water!
Sign up to see the contentIt's free!
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Improve your grades
Join milions of students
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Natural Polymers - The Chemistry of Life
Your body is basically a walking chemistry lab filled with amazing natural polymers! Amino acids are like biological building blocks that join together through condensation polymerisation to create proteins. Each amino acid has two functional groups that can link up, and when they do, they release water molecules.
DNA is probably the most important polymer you'll ever encounter - it's made from four different monomers called nucleotides arranged in that famous double helix structure. This incredible molecule stores all the genetic instructions that make you... well, you!
Other natural polymers are everywhere around you. Starch and cellulose are both made from glucose monomers - starch stores energy in plants whilst cellulose gives them structure. It's amazing how the same building block can create completely different materials!
Real-World Connection: Every time you eat bread (starch), wear a cotton shirt (cellulose), or literally just exist (proteins and DNA), you're experiencing the power of natural polymerisation!
Sign up to see the contentIt's free!
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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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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