Maths
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Britain & the wider world: 1745 -1901
1l the quest for political stability: germany, 1871-1991
The cold war
Inter-war germany
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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
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2s the making of modern britain, 1951-2007
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Sophieeee 🎀👝🛍🌺💓
05/12/2025
Chemistry
Intermolecular Bonds: LDF, PDPD, Hydrogen Bonding Higher Chem Unit 1
220
•
5 Dec 2025
•
Sophieeee 🎀👝🛍🌺💓
@sophiesnotes
Intermolecular bonds are the forces that hold molecules together, distinct... Show more
Intermolecular bonds occur between separate molecules and are weaker than the bonds within molecules. These Van der Waals forces come in three main types, with increasing strength: London Dispersion forces, Permanent dipole-Permanent dipole interactions, and Hydrogen bonding.
London Dispersion forces are the weakest type but exist between all atoms and molecules. They explain why even noble gases and molecular elements can condense into liquids and solids at low temperatures. These forces arise from temporary uneven distributions of electrons, creating momentary δ+ and δ- regions that attract neighboring molecules.
The strength of London Dispersion forces increases with molecular size. Larger atoms and molecules have more electrons, which can create stronger temporary dipoles and therefore stronger attractions between molecules.
Remember this: London Dispersion forces are universal – they occur between all molecules regardless of structure, unlike other intermolecular forces which require specific molecular features.
Polar molecules have permanent dipoles – regions of partial positive and negative charge that don't shift over time. When these molecules encounter each other, the positive end of one molecule attracts the negative end of another, creating permanent dipole-permanent dipole interactions.
These interactions are stronger than London Dispersion forces when comparing molecules with similar numbers of electrons. You'll find them in molecules with certain shapes: linear, angular, and trigonal pyramidal compounds containing polar bonds will be polar overall.
Molecular shape determines whether a molecule is polar. For example, tetrahedral molecules with four identical groups around the central atom (like CCl₄) are non-polar despite having polar bonds, because the bond dipoles cancel out. However, if one group differs (like in CHCl₃), the molecule becomes polar.
Quick tip: To determine if permanent dipole interactions will occur, first check if the molecule has polar bonds, then analyze its shape to see if those bond dipoles create an overall molecular dipole.
Hydrogen bonding is the strongest type of intermolecular bond. These special permanent dipole interactions occur when hydrogen is bonded to highly electronegative atoms: nitrogen, oxygen, or fluorine . Common examples include water, ammonia, alcohols, and alkanoic acids.
The exceptional strength of hydrogen bonds significantly impacts physical properties. Substances with hydrogen bonding have much higher melting and boiling points than you'd expect based on their molecular size and electron count alone. This explains why water, despite its small molecular size, has surprisingly high boiling and melting points.
Van der Waals forces increase in strength from London Dispersion forces (weakest) to permanent dipole-permanent dipole interactions to hydrogen bonding (strongest). However, even the strongest intermolecular forces are weaker than actual covalent bonds that hold atoms together within molecules.
Exam focus: Questions often ask you to explain physical property differences between similar compounds. If one can form hydrogen bonds while the other cannot, this is usually the key to explaining boiling point differences.
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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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
Sophieeee 🎀👝🛍🌺💓
@sophiesnotes
Intermolecular bonds are the forces that hold molecules together, distinct from the bonds within molecules themselves. These forces, collectively known as Van der Waals forces, vary in strength and play crucial roles in determining the physical properties of substances like... Show more
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Intermolecular bonds occur between separate molecules and are weaker than the bonds within molecules. These Van der Waals forces come in three main types, with increasing strength: London Dispersion forces, Permanent dipole-Permanent dipole interactions, and Hydrogen bonding.
London Dispersion forces are the weakest type but exist between all atoms and molecules. They explain why even noble gases and molecular elements can condense into liquids and solids at low temperatures. These forces arise from temporary uneven distributions of electrons, creating momentary δ+ and δ- regions that attract neighboring molecules.
The strength of London Dispersion forces increases with molecular size. Larger atoms and molecules have more electrons, which can create stronger temporary dipoles and therefore stronger attractions between molecules.
Remember this: London Dispersion forces are universal – they occur between all molecules regardless of structure, unlike other intermolecular forces which require specific molecular features.
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Polar molecules have permanent dipoles – regions of partial positive and negative charge that don't shift over time. When these molecules encounter each other, the positive end of one molecule attracts the negative end of another, creating permanent dipole-permanent dipole interactions.
These interactions are stronger than London Dispersion forces when comparing molecules with similar numbers of electrons. You'll find them in molecules with certain shapes: linear, angular, and trigonal pyramidal compounds containing polar bonds will be polar overall.
Molecular shape determines whether a molecule is polar. For example, tetrahedral molecules with four identical groups around the central atom (like CCl₄) are non-polar despite having polar bonds, because the bond dipoles cancel out. However, if one group differs (like in CHCl₃), the molecule becomes polar.
Quick tip: To determine if permanent dipole interactions will occur, first check if the molecule has polar bonds, then analyze its shape to see if those bond dipoles create an overall molecular dipole.
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Hydrogen bonding is the strongest type of intermolecular bond. These special permanent dipole interactions occur when hydrogen is bonded to highly electronegative atoms: nitrogen, oxygen, or fluorine . Common examples include water, ammonia, alcohols, and alkanoic acids.
The exceptional strength of hydrogen bonds significantly impacts physical properties. Substances with hydrogen bonding have much higher melting and boiling points than you'd expect based on their molecular size and electron count alone. This explains why water, despite its small molecular size, has surprisingly high boiling and melting points.
Van der Waals forces increase in strength from London Dispersion forces (weakest) to permanent dipole-permanent dipole interactions to hydrogen bonding (strongest). However, even the strongest intermolecular forces are weaker than actual covalent bonds that hold atoms together within molecules.
Exam focus: Questions often ask you to explain physical property differences between similar compounds. If one can form hydrogen bonds while the other cannot, this is usually the key to explaining boiling point differences.
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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Explore the fundamentals of London Dispersion Forces (LDFs), the weakest type of intermolecular forces. This summary covers the formation of temporary dipoles, the role of electron movement, and how these forces affect the properties of non-polar molecules, including their low melting and boiling points. Ideal for students studying higher chemistry concepts.
ChemistryExplore the key types of intermolecular forces, including London dispersion forces, dipole-dipole interactions, and hydrogen bonding. This summary highlights their mechanisms, strengths, and effects on physical properties like boiling points, tailored for AQA A-level Chemistry students.
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ChemistryComprehensive resource for Year 12 students pursuing a Level 3 Diploma in Applied Science. This booklet covers essential topics including cell structure, chemical properties, and wave theory, providing clear explanations and key concepts to aid in your studies and exam preparation.
ChemistryExplore the principles of electrolysis, including redox reactions, half-reactions, and the roles of anodes and cathodes. This summary covers key concepts such as electrolytic cells, Faraday's laws, and the significance of electrolytes in conducting electricity. Ideal for students preparing for exams or seeking a clear understanding of electrolysis processes.
ChemistryComprehensive A Level Chemistry summary covering key concepts of bonding types, molecular shapes, electronegativity, and intermolecular forces. Understand ionic, covalent, and dative bonds, along with their properties and effects on molecular behavior. Ideal for exam preparation and revision.
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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 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