•

23 Dec 2025

•

3 pages

Understanding Intermolecular Forces for AQA Chemistry

hammerbro

@hammerbro

Ever wonder why water boils at 100°C whilst other similar... Show more

1 / 3

Intermolecular Forces - AQA A-Level Chemistry.

Intermolecular forces are forces between molecules tohold them together
They are very weak-m

Understanding Intermolecular Forces

Think of intermolecular forces as the "glue" that holds molecules together, though they're much weaker than the bonds within molecules themselves. These forces might be weak, but they're absolutely crucial for determining how substances behave in the real world.

There are three main types you need to know: Van der Waals forces (the weakest), permanent dipole-dipole interactions (medium strength), and hydrogen bonding (the strongest). Each one works differently and affects substances in unique ways.

Van der Waals forces are the most basic type - they exist between all molecules and even noble gas atoms. As molecules get larger, these forces become stronger because there's more surface area for attraction. This explains why helium boils at -269°C whilst xenon boils at -108°C.

Quick Check: Remember that molecular size directly affects Van der Waals forces - bigger molecules = stronger forces = higher boiling points!

Dipole Interactions and Hydrogen Bonding

Permanent dipole-dipole interactions occur when molecules have uneven charge distribution due to differences in electronegativity. Picture HCl molecules lining up so the slightly positive hydrogen end attracts the slightly negative chlorine end of neighbouring molecules.

Hydrogen bonding takes this concept further and creates the strongest intermolecular force. It only happens when hydrogen is bonded to fluorine, oxygen, or nitrogen - the three most electronegative elements. The hydrogen's positive charge attracts lone pairs of electrons on these atoms.

Water perfectly demonstrates hydrogen bonding in action. These special bonds give water its unique properties: ice is less dense than liquid water (creating the lattice structure that makes ice float), water has an unusually high boiling point, and it shows remarkable surface tension.

Real-World Connection: Without hydrogen bonding, water would boil at around -80°C, making life on Earth impossible!

Patterns in Hydrides and Key Rules

Looking at hydrides (compounds of hydrogen with other elements) reveals fascinating patterns. In Groups 5, 6, and 7, the first member always has a much higher boiling point than expected - NH₃, H₂O, and HF all break the trend because of hydrogen bonding.

For other hydrides moving down each group, two competing factors battle it out. Polarity decreases (weakening dipole forces) whilst molecular size increases (strengthening Van der Waals forces). The size effect usually wins, explaining why H₂Te boils higher than H₂S.

Here are the essential rules you need to remember: all molecules have Van der Waals forces as a baseline, polar molecules add dipole-dipole forces on top, and hydrogen bonding only occurs with F, O, or N. These forces directly determine physical properties like boiling points, melting points, and solubility.

Exam Tip: When predicting boiling points, first check for hydrogen bonding, then consider molecular size and polarity - this approach works every time!

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.

Most popular content in Chemistry

BTEC Applied Science Unit 1 Overview

Comprehensive 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.

Chemistry

Paper 1 Flashcards for GCSE AQA Higher

Chemistry Paper 1 Flashcards for AQA Higher content

Chemistry

Chemistry paper 1 AQA

Condensed notes.

Chemistry

GCSE Chemistry Revision Notes

AQA GCSE Combined Chemistry * detailed summary

Chemistry

A-level OCR A Chemistry summary sheets

Everything from snaprevise for OCR chemistry a-level

Chemistry

Understanding Phase Transitions

Explore the key concepts of phase transitions in matter, including sublimation, melting, boiling, evaporation, and condensation. This summary covers the characteristics of solids, liquids, and gases, their unique properties, and the specific temperatures at which phase changes occur. Ideal for GCSE Chemistry students seeking to grasp the fundamentals of states of matter.

Chemistry

N5 Chemistry: Bonding & Reactions

Explore essential concepts in National 5 Chemistry, including atomic structure, types of bonding (ionic and covalent), reaction rates, and acid-base chemistry. This comprehensive guide covers key topics such as chemical equations, molarity, and neutralization reactions, providing a solid foundation for your studies.

Chemistry

GCSE Chemistry Overview

Explore key concepts in GCSE Chemistry, including atomic structure, chemical bonding, organic chemistry, and reaction rates. This comprehensive mindmap covers essential topics such as the Haber process, electrolysis, and energy changes, providing a clear understanding of the subject. Ideal for AQA Chemistry students preparing for exams.

Chemistry

Redox Reactions Overview

Explore the fundamentals of redox reactions, including oxidation states, definitions of oxidation and reduction, and the roles of oxidizing and reducing agents. This summary covers key rules for determining oxidation states, the concept of disproportionation, and practical applications in chemical equations. Ideal for A-Level Chemistry students preparing for exams.

Chemistry

Most popular content

An Inspector Calls: Character Insights

Explore in-depth analysis and key quotes for characters in J.B. Priestley's 'An Inspector Calls'. This resource covers Gerald Croft, Inspector Goole, Sheila Birling, Mrs. Birling, Eric Birling, and Eva Smith, focusing on themes of class, gender roles, and social responsibility. Ideal for students aiming for Grade 8 and above.

English Literature

aqa higher tier combined science - biology b1 : cell biology, paper 1

b1: cell biology - paper 1

Biology

Sociology of Families: Comprehensive Revision

Dive into an extensive overview of family dynamics, perspectives, and patterns in sociology. This resource covers key concepts such as family diversity, gender roles, marriage, and the impact of social policies on family structures. Perfect for A-Level Sociology students preparing for Paper 2.

Sociology

Comprehensive Crime & Deviance Overview

Explore an extensive revision of crime and deviance topics, including theories, types of crime, and the impact of media. This resource covers key concepts such as Marxism, functionalism, gender and crime, and the influence of globalization on criminal behavior. Ideal for students seeking a thorough understanding of criminology and its various theories. Type: Full Topic Revision.

Sociology

Sociology of Education Overview

Explore comprehensive A-Level Sociology notes on the education system, covering key theories, policies, and sociological perspectives. This resource includes insights on marketisation, gender roles, cultural deprivation, and educational inequalities, providing a thorough understanding of how education shapes social stratification and individual achievement. Ideal for exam preparation and in-depth study.

Sociology

Criminal Justice Evidence Rules

Explore the essential rules governing the use of evidence in criminal cases, including reliability, admissibility, and relevance. This summary covers key concepts such as the roles of personnel in investigations, the impact of witness testimonies, and the implications of plea bargaining. Ideal for Year 13 criminology students preparing for assessments.

Criminology

Biology Paper 1 Overview

Comprehensive study notes covering key concepts in cellular biology, human digestion, respiration, photosynthesis, and the circulatory system. This resource includes detailed explanations of cell structures, enzyme functions, nutrient absorption, and the impact of environmental factors on biological processes. Ideal for students preparing for Biology Paper 1 exams.

Biology

Macbeth: Guilt and Ambition

Explore the complex themes of guilt and ambition in Shakespeare's 'Macbeth'. This analysis covers key characters, including Macbeth and Lady Macbeth, their moral dilemmas, and the tragic consequences of their ambition. Ideal for students studying character motivations, thematic elements, and the psychological impact of power. Includes insights on the natural order, manipulation, and the descent into madness.

English Literature

Language Paper 1 Strategies

Master the AQA English Language Paper 1 with this comprehensive guide. Explore key strategies for language and structural analysis, critical evaluation, and creative writing. Learn how to effectively analyze texts, utilize literary techniques, and enhance your writing skills to excel in your exams.

English Language

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

Stefan S

iOS user

Samantha Klich

Android user

Anna

iOS user

Best app on earth! no words because it’s too good

Thomas R

iOS user

Basil

Android user

David K

iOS user

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

Rohan U

Android user

Xander S

iOS user

Elisha

iOS user

Paul T

iOS user

Chemistry

•

173

•

23 Dec 2025

•

3 pages

Understanding Intermolecular Forces for AQA Chemistry

hammerbro

@hammerbro

Ever wonder why water boils at 100°C whilst other similar molecules boil at much lower temperatures? It's all down to intermolecular forces - the invisible attractions between molecules that determine how substances behave. Understanding these forces will help you predict... 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

Understanding Intermolecular Forces

Quick Check: Remember that molecular size directly affects Van der Waals forces - bigger molecules = stronger forces = higher boiling points!

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

Dipole Interactions and Hydrogen Bonding

Real-World Connection: Without hydrogen bonding, water would boil at around -80°C, making life on Earth impossible!

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

Patterns in Hydrides and Key Rules

Exam Tip: When predicting boiling points, first check for hydrogen bonding, then consider molecular size and polarity - this approach works every time!