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Britain & the wider world: 1745 -1901
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Chemistry
8 Dec 2025
219
2 pages
Maya A @maya.ah
Infrared spectroscopy is like giving molecules a health check-up using light waves. By shining infrared radiation through a... Show more
Think of covalent bonds as tiny springs that are constantly vibrating. When you shine infrared light through a compound, these bonds absorb energy at specific frequencies and vibrate even more. It's a bit like how different guitar strings vibrate at different pitches.
The vibration frequency depends on three key factors how heavy the atoms are, how strong the bond is, and what type of vibration occurs. Stronger bonds vibrate faster (higher frequency), whilst heavier atoms make bonds vibrate more slowly (lower frequency).
There are three main types of bond vibrations you need to know symmetric stretch (both ends moving outward together), asymmetric stretch (one end moving out whilst the other moves in), and bending (the bond angle changing).
Quick Tip Remember that stronger = faster vibrations, heavier atoms = slower vibrations.
Scientists measure these vibrations using wavenumbers (cm⁻¹) on the x-axis, which is proportional to frequency. Most useful IR absorption happens between 4,000-400 cm⁻¹.
IR spectra are split into two main regions that serve different purposes. Above 1500 cm⁻¹ is where you'll identify functional groups - this is the money zone for working out what's in your compound.
Here are the key peaks you absolutely must memorise O-H bonds in alcohols appear at 3,230-3,550 cm⁻¹, C=O bonds show up at 1,680-1,750 cm⁻¹, and C=C bonds appear at 1,620-1,680 cm⁻¹. N-H bonds in amines create peaks around 3,300-3,500 cm⁻¹.
Below 1500 cm⁻¹ is the fingerprint region - it's incredibly complex with loads of peaks caused by the whole molecule vibrating. This region is unique for every compound, so chemists use computers to match it against databases to identify unknown substances.
Remember Strongly polar bonds give intense peaks, and hydrogen bonding creates broad, spread-out bands.
IR spectroscopy also explains global warming. Greenhouse gases like CO₂ and methane have bonds that absorb infrared radiation really effectively, trapping heat that Earth tries to radiate back to space.
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.
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Explore the detailed process of synthesizing aspirin from salicylic acid and ethanoic anhydride, including essential laboratory techniques such as reflux, crystallization, and filtration. This study note covers methods for testing the purity of aspirin using melting point analysis and thin-layer chromatography (TLC). Ideal for AQA Organic Chemistry students focusing on carboxylic acids and esters.
ChemistryExplore comprehensive AQA A-Level Chemistry tests covering functional groups, transition metals, and ion tests. This resource includes detailed observations and reactions for various chemical tests, ideal for exam preparation and revision. Perfect for students seeking to enhance their understanding of laboratory techniques and chemical nomenclature.
ChemistryExplore the detailed process of mass spectrometry, including ionization methods like Electron Impact and Electrospray, acceleration of ions, and detection techniques. This summary covers key concepts such as mass spectrum, ionization energy, and molecular fragmentation, providing a comprehensive overview for students studying analytical chemistry.
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
Maya A
@maya.ah
Infrared spectroscopy is like giving molecules a health check-up using light waves. By shining infrared radiation through a sample, chemists can identify what functional groups are present and even work out what unknown compounds are.
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By signing up you accept Terms of Service and Privacy Policy
Think of covalent bonds as tiny springs that are constantly vibrating. When you shine infrared light through a compound, these bonds absorb energy at specific frequencies and vibrate even more. It's a bit like how different guitar strings vibrate at different pitches.
The vibration frequency depends on three key factors: how heavy the atoms are, how strong the bond is, and what type of vibration occurs. Stronger bonds vibrate faster (higher frequency), whilst heavier atoms make bonds vibrate more slowly (lower frequency).
There are three main types of bond vibrations you need to know: symmetric stretch (both ends moving outward together), asymmetric stretch (one end moving out whilst the other moves in), and bending (the bond angle changing).
Quick Tip: Remember that stronger = faster vibrations, heavier atoms = slower vibrations.
Scientists measure these vibrations using wavenumbers (cm⁻¹) on the x-axis, which is proportional to frequency. Most useful IR absorption happens between 4,000-400 cm⁻¹.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
IR spectra are split into two main regions that serve different purposes. Above 1500 cm⁻¹ is where you'll identify functional groups - this is the money zone for working out what's in your compound.
Here are the key peaks you absolutely must memorise: O-H bonds in alcohols appear at 3,230-3,550 cm⁻¹, C=O bonds show up at 1,680-1,750 cm⁻¹, and C=C bonds appear at 1,620-1,680 cm⁻¹. N-H bonds in amines create peaks around 3,300-3,500 cm⁻¹.
Below 1500 cm⁻¹ is the fingerprint region - it's incredibly complex with loads of peaks caused by the whole molecule vibrating. This region is unique for every compound, so chemists use computers to match it against databases to identify unknown substances.
Remember: Strongly polar bonds give intense peaks, and hydrogen bonding creates broad, spread-out bands.
IR spectroscopy also explains global warming. Greenhouse gases like CO₂ and methane have bonds that absorb infrared radiation really effectively, trapping heat that Earth tries to radiate back to space.
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.
7
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Explore the detailed process of synthesizing aspirin from salicylic acid and ethanoic anhydride, including essential laboratory techniques such as reflux, crystallization, and filtration. This study note covers methods for testing the purity of aspirin using melting point analysis and thin-layer chromatography (TLC). Ideal for AQA Organic Chemistry students focusing on carboxylic acids and esters.
ChemistryExplore comprehensive AQA A-Level Chemistry tests covering functional groups, transition metals, and ion tests. This resource includes detailed observations and reactions for various chemical tests, ideal for exam preparation and revision. Perfect for students seeking to enhance their understanding of laboratory techniques and chemical nomenclature.
ChemistryExplore the detailed process of mass spectrometry, including ionization methods like Electron Impact and Electrospray, acceleration of ions, and detection techniques. This summary covers key concepts such as mass spectrum, ionization energy, and molecular fragmentation, providing a comprehensive overview for students studying analytical chemistry.
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
Sociology