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1l the quest for political stability: germany, 1871-1991
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Chemistry
4 Dec 2025
862
2 pages
samira choudhury @samirachoudhury_htne
Organic chemistry might sound complicated, but it's actually about understanding the molecules that power our world - from... Show more
Hydrocarbons are molecules made entirely of hydrogen and carbon atoms, and they come in two main types you need to know. Alkanes have only single bonds between carbon atoms and follow the formula CnH2n+2, whilst alkenes contain at least one double bond and follow the formula CnH2n.
The first four alkanes are methane (CH4), ethane (C2H6), propane (C3H8), and butane (C4H10). These belong to a homologous series - basically a family of compounds that all behave similarly because they have the same functional group.
Here's something brilliant as hydrocarbon chains get longer, their properties change in predictable ways. Shorter chains are runny (less viscous), easier to ignite, and have lower boiling points because they're more volatile. Longer chains are the opposite - thicker, harder to light, and need higher temperatures to boil.
Key Point Each carbon atom always forms exactly four covalent bonds, which explains why hydrocarbons have such regular patterns in their formulae.
When hydrocarbons burn completely with enough oxygen, they undergo complete combustion and release loads of energy. This produces only carbon dioxide and water vapour, which is why hydrocarbons make excellent fuels for everything from cars to central heating.
Crude oil formed over millions of years from dead sea creatures (mainly plankton) that got buried under mud and cooked by underground heat and pressure. It's a fossil fuel and a finite resource that we're using up rapidly.
Fractional distillation separates crude oil into useful fractions. The oil gets heated until it becomes gas, then rises up a fractionating column that's hot at the bottom and cool at the top. Longer hydrocarbons have higher boiling points, so they condense and drain out near the bottom, whilst shorter ones rise higher before condensing.
Cracking is the process of breaking long, useless hydrocarbon chains into shorter, more valuable ones. Long chains are thick and gloopy (like tar), but short chains make brilliant fuels because they're flammable and in high demand.
Lab Test You can identify alkenes using bromine water - it turns from orange to colourless when mixed with alkenes, but stays orange with alkanes.
There are two main cracking methods catalytic cracking (using hot aluminium oxide catalyst) and steam cracking (mixing with steam at very high temperatures). Both are thermal decomposition reactions that break molecules apart using heat, and they produce both alkanes and the more reactive alkenes that are essential for making plastics and other materials.
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.
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Explore the essential concepts of hydrocarbons, including alkanes and alkenes, their structures, properties, and the processes of fractional distillation and cracking. This summary provides a clear overview for GCSE Chemistry students, focusing on the formation and significance of crude oil and its components.
ChemistryExplore the process of hydrocarbon cracking, including the breakdown of long-chain hydrocarbons into smaller, useful molecules. Understand the differences between alkenes and alkanes, their structures, and properties. This summary covers key concepts such as supply and demand in fractional distillation, the formation of ethene, and the significance of saturated vs. unsaturated hydrocarbons. Ideal for GCSE Chemistry students preparing for Edexcel exams.
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
samira choudhury
@samirachoudhury_htne
Organic chemistry might sound complicated, but it's actually about understanding the molecules that power our world - from the petrol in cars to the plastic in your phone. This topic focuses on hydrocarbons, which are simple compounds made of just... Show more
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By signing up you accept Terms of Service and Privacy Policy
Hydrocarbons are molecules made entirely of hydrogen and carbon atoms, and they come in two main types you need to know. Alkanes have only single bonds between carbon atoms and follow the formula CnH2n+2, whilst alkenes contain at least one double bond and follow the formula CnH2n.
The first four alkanes are methane (CH4), ethane (C2H6), propane (C3H8), and butane (C4H10). These belong to a homologous series - basically a family of compounds that all behave similarly because they have the same functional group.
Here's something brilliant: as hydrocarbon chains get longer, their properties change in predictable ways. Shorter chains are runny (less viscous), easier to ignite, and have lower boiling points because they're more volatile. Longer chains are the opposite - thicker, harder to light, and need higher temperatures to boil.
Key Point: Each carbon atom always forms exactly four covalent bonds, which explains why hydrocarbons have such regular patterns in their formulae.
When hydrocarbons burn completely with enough oxygen, they undergo complete combustion and release loads of energy. This produces only carbon dioxide and water vapour, which is why hydrocarbons make excellent fuels for everything from cars to central heating.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Crude oil formed over millions of years from dead sea creatures (mainly plankton) that got buried under mud and cooked by underground heat and pressure. It's a fossil fuel and a finite resource that we're using up rapidly.
Fractional distillation separates crude oil into useful fractions. The oil gets heated until it becomes gas, then rises up a fractionating column that's hot at the bottom and cool at the top. Longer hydrocarbons have higher boiling points, so they condense and drain out near the bottom, whilst shorter ones rise higher before condensing.
Cracking is the process of breaking long, useless hydrocarbon chains into shorter, more valuable ones. Long chains are thick and gloopy (like tar), but short chains make brilliant fuels because they're flammable and in high demand.
Lab Test: You can identify alkenes using bromine water - it turns from orange to colourless when mixed with alkenes, but stays orange with alkanes.
There are two main cracking methods: catalytic cracking (using hot aluminium oxide catalyst) and steam cracking (mixing with steam at very high temperatures). Both are thermal decomposition reactions that break molecules apart using heat, and they produce both alkanes and the more reactive alkenes that are essential for making plastics and other materials.
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.
14
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Explore the essential concepts of hydrocarbons, including alkanes and alkenes, their structures, properties, and the processes of fractional distillation and cracking. This summary provides a clear overview for GCSE Chemistry students, focusing on the formation and significance of crude oil and its components.
ChemistryExplore the process of hydrocarbon cracking, including the breakdown of long-chain hydrocarbons into smaller, useful molecules. Understand the differences between alkenes and alkanes, their structures, and properties. This summary covers key concepts such as supply and demand in fractional distillation, the formation of ethene, and the significance of saturated vs. unsaturated hydrocarbons. Ideal for GCSE Chemistry students preparing for Edexcel exams.
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
