Organic Chemistry in GCSE AQA: Hydrocarbons and Crude Oil Processing... Show more
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
72
1
G
George
14/08/2025
Chemistry
GCSE AQA Chemistry Organic Chemistry (C7)
1,837
•
14 Aug 2025
•
Free GCSE AQA Chemistry Organic Chemistry Revision Notes PDF - Fractional Distillation Explained & Hydrocarbons Properties
G
George
@george_aakl
Fractional Distillation and Cracking
This section delves deeper into the fractional distillation process and introduces the concept of cracking, both essential topics for GCSE Organic Chemistry questions.
Fractional Distillation in Detail
The fractionating column used in the distillation process has a temperature gradient, with the hottest part at the bottom and the coldest at the top. As the crude oil vapor rises through the column, it cools gradually, allowing different compounds to condense at different levels.
Highlight: Hydrocarbons with similar numbers of carbon atoms have similar boiling points, so they condense at similar levels in the column.
The groups of hydrocarbons that condense together are called fractions. These fractions are continuously tapped off from the column at their respective condensation levels.
Example: Some common fractions include LPG, petrol, kerosene (jet fuel), diesel oil, and bitumen.
The uses of these fractions depend on their properties, which is a crucial concept for answering Organic chemistry GCSE AQA exam questions.
Cracking Crude Oil
Cracking is another important process in the refining of crude oil, turning longer hydrocarbon molecules into smaller, more useful ones.
Definition: Cracking is a thermal decomposition reaction that breaks down molecules by heating them.
There are two main methods of cracking:
- Catalytic cracking: Uses a hot, powdered catalyst (e.g., aluminium oxide)
- Steam cracking: Mixes the vapor with steam and heats it to a very high temperature
Highlight: Cracking produces substances like ethene, which are essential for making plastics, making it a key topic in GCSE AQA Chemistry paper 1 revision notes.
Understanding these processes is crucial for students preparing for their GCSE Chemistry fractional distillation questions and other related topics in organic chemistry.
Page 3: Cracking Processes and Applications
The final page focuses on cracking processes, explaining how larger hydrocarbon molecules are broken down into smaller, more useful ones.
Definition: Cracking is a thermal decomposition reaction that breaks down larger hydrocarbon molecules into smaller ones.
Vocabulary: Catalytic cracking uses catalysts like aluminium oxide, while steam cracking employs high-temperature steam.
Highlight: The process produces valuable products like ethene, which is essential for plastic production.
The page provides detailed explanations of both catalytic and steam cracking methods, including their industrial applications and importance in modern chemistry.
Hydrocarbons and Alkanes
Organic Chemistry forms a crucial part of the AQA GCSE Chemistry syllabus. This section focuses on hydrocarbons and alkanes, providing essential information for students preparing for their exams.
Hydrocarbons are molecules composed solely of carbon and hydrogen atoms. Alkanes, a type of hydrocarbon, consist of carbon chains surrounded by hydrogen atoms, with no carbon-carbon double bonds.
Definition: Alkanes are saturated hydrocarbons, meaning all atoms have formed bonds with as many other atoms as possible.
The first four alkanes are methane, ethane, propane, and butane. Their molecular structures are illustrated in the text, showing the arrangement of carbon and hydrogen atoms.
Vocabulary: The general formula for alkanes is CnH₂n+2, where n represents the number of carbon atoms.
Properties of hydrocarbons vary based on their molecular structure:
- Shorter molecules are less viscous (runnier).
- Shorter molecules have lower boiling points.
- Shorter molecules are more flammable.
Highlight: Understanding these properties is crucial for answering GCSE Chemistry fractional distillation questions.
The complete combustion of hydrocarbons produces carbon dioxide and water vapor, which is an important concept in Organic Chemistry GCSE AQA exam questions.
Fractional Distillation of Crude Oil
Crude oil, a finite resource formed from ancient organic matter, is a mixture of various hydrocarbon compounds. The process of separating these compounds is called fractional distillation.
Definition: Fractional distillation is the technique of splitting crude oil into separate groups of hydrocarbons based on their boiling points.
The process involves:
- Heating crude oil until it evaporates
- Pumping the vapor into a fractionating column with a temperature gradient
- Allowing different compounds to condense at different levels based on their boiling points
Example: Lighter fractions like LPG (Liquefied Petroleum Gas) condense at the top of the column, while heavier fractions like bitumen condense at the bottom.
This process is crucial for producing various fuels and organic compounds used in modern society, making it a key topic in GCSE AQA Chemistry organic chemistry revision.
We thought you’d 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 – all at your fingertips.
Can't find what you're looking for? Explore other subjects.
Students love us — 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 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
Free GCSE AQA Chemistry Organic Chemistry Revision Notes PDF - Fractional Distillation Explained & Hydrocarbons Properties
G
George
@george_aakl
Organic Chemistry in GCSE AQA: Hydrocarbons and Crude Oil Processing
A comprehensive overview of Organic Chemistry GCSEfundamentals, focusing on hydrocarbons, crude oil processing, and related chemical processes. This guide covers essential topics from basic hydrocarbon structures to complex industrial... Show more
Fractional Distillation and Cracking
This section delves deeper into the fractional distillation process and introduces the concept of cracking, both essential topics for GCSE Organic Chemistry questions.
Fractional Distillation in Detail
The fractionating column used in the distillation process has a temperature gradient, with the hottest part at the bottom and the coldest at the top. As the crude oil vapor rises through the column, it cools gradually, allowing different compounds to condense at different levels.
Highlight: Hydrocarbons with similar numbers of carbon atoms have similar boiling points, so they condense at similar levels in the column.
The groups of hydrocarbons that condense together are called fractions. These fractions are continuously tapped off from the column at their respective condensation levels.
Example: Some common fractions include LPG, petrol, kerosene (jet fuel), diesel oil, and bitumen.
The uses of these fractions depend on their properties, which is a crucial concept for answering Organic chemistry GCSE AQA exam questions.
Cracking Crude Oil
Cracking is another important process in the refining of crude oil, turning longer hydrocarbon molecules into smaller, more useful ones.
Definition: Cracking is a thermal decomposition reaction that breaks down molecules by heating them.
There are two main methods of cracking:
- Catalytic cracking: Uses a hot, powdered catalyst (e.g., aluminium oxide)
- Steam cracking: Mixes the vapor with steam and heats it to a very high temperature
Highlight: Cracking produces substances like ethene, which are essential for making plastics, making it a key topic in GCSE AQA Chemistry paper 1 revision notes.
Understanding these processes is crucial for students preparing for their GCSE Chemistry fractional distillation questions and other related topics in organic chemistry.
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
Page 3: Cracking Processes and Applications
The final page focuses on cracking processes, explaining how larger hydrocarbon molecules are broken down into smaller, more useful ones.
Definition: Cracking is a thermal decomposition reaction that breaks down larger hydrocarbon molecules into smaller ones.
Vocabulary: Catalytic cracking uses catalysts like aluminium oxide, while steam cracking employs high-temperature steam.
Highlight: The process produces valuable products like ethene, which is essential for plastic production.
The page provides detailed explanations of both catalytic and steam cracking methods, including their industrial applications and importance in modern chemistry.
Hydrocarbons and Alkanes
Organic Chemistry forms a crucial part of the AQA GCSE Chemistry syllabus. This section focuses on hydrocarbons and alkanes, providing essential information for students preparing for their exams.
Hydrocarbons are molecules composed solely of carbon and hydrogen atoms. Alkanes, a type of hydrocarbon, consist of carbon chains surrounded by hydrogen atoms, with no carbon-carbon double bonds.
Definition: Alkanes are saturated hydrocarbons, meaning all atoms have formed bonds with as many other atoms as possible.
The first four alkanes are methane, ethane, propane, and butane. Their molecular structures are illustrated in the text, showing the arrangement of carbon and hydrogen atoms.
Vocabulary: The general formula for alkanes is CnH₂n+2, where n represents the number of carbon atoms.
Properties of hydrocarbons vary based on their molecular structure:
- Shorter molecules are less viscous (runnier).
- Shorter molecules have lower boiling points.
- Shorter molecules are more flammable.
Highlight: Understanding these properties is crucial for answering GCSE Chemistry fractional distillation questions.
The complete combustion of hydrocarbons produces carbon dioxide and water vapor, which is an important concept in Organic Chemistry GCSE AQA exam questions.
Fractional Distillation of Crude Oil
Crude oil, a finite resource formed from ancient organic matter, is a mixture of various hydrocarbon compounds. The process of separating these compounds is called fractional distillation.
Definition: Fractional distillation is the technique of splitting crude oil into separate groups of hydrocarbons based on their boiling points.
The process involves:
- Heating crude oil until it evaporates
- Pumping the vapor into a fractionating column with a temperature gradient
- Allowing different compounds to condense at different levels based on their boiling points
Example: Lighter fractions like LPG (Liquefied Petroleum Gas) condense at the top of the column, while heavier fractions like bitumen condense at the bottom.
This process is crucial for producing various fuels and organic compounds used in modern society, making it a key topic in GCSE AQA Chemistry organic chemistry revision.
We thought you’d 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 – all at your fingertips.
Can't find what you're looking for? Explore other subjects.
Students love us — 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 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