Chemistry is all around you - from the air you... Show more
Chemistry238 views·Updated Jun 2, 2026·5 pagesAQA Combined Science Chemistry Paper 2: Higher Tier
Faye Findlay@fayefindlay_ylvf
1 / 5
1
of 5
Rate of Reaction & Equilibrium
Ever wondered why some reactions happen instantly whilst others take ages? The rate of reaction measures how quickly reactants transform into products, and it's all about particle collisions.
Collision theory explains that particles must crash into each other with enough energy to create a successful reaction. You can speed things up by increasing temperature (particles move faster), concentration (more particles in the same space), pressure (particles squashed together), or surface area (more exposed reaction sites).
Catalysts are like chemical matchmakers - they speed up reactions without getting used up themselves. Meanwhile, reversible reactions reach equilibrium when the forward and backward reactions happen at the same rate, shown by the ⇌ symbol.
Key Tip: Remember that Le Chatelier's Principle means equilibrium systems always fight back against changes - if you increase pressure, the system shifts to reduce it!
2
of 5
Hydrocarbons & Crude Oil
Hydrocarbons are simple compounds made only of carbon and hydrogen atoms, but they power our entire world! The simplest type, alkanes, follow the formula CnH2n+2 - from methane (CH4) to butane (C4H10).
Crude oil is ancient plankton that's been cooking underground for millions of years. We extract this non-renewable treasure through fractional distillation - heating it up so different compounds evaporate at different temperatures.
Longer hydrocarbon chains are thick and less flammable, whilst shorter ones are runny and highly flammable. That's why we use cracking to split long chains into more useful shorter ones and reactive alkenes.
Remember: In fractional distillation, it's hotter at the bottom (longer hydrocarbons) and cooler at the top (shorter hydrocarbons) - think of it like a chemical skyscraper!
3
of 5
Purity & Chemical Analysis
Pure substances are chemistry's perfectionists - they contain only one compound or element and melt or boil at exact temperatures. But most useful materials are actually formulations - carefully designed mixtures that do specific jobs perfectly.
Chromatography is your detective tool for separating mixtures. It works using a mobile phase (where molecules can move) and a stationary phase (where they can't), letting you identify mystery substances.
You can also identify gases using simple tests: chlorine turns damp litmus paper white, oxygen relights a glowing splint, and carbon dioxide makes limewater go cloudy.
Pro Tip: The further a substance travels in chromatography, the more soluble it is in the mobile phase - use this to identify unknown compounds!
4
of 5
Chemistry of the Atmosphere
Our atmosphere wasn't always perfect for life - it evolved through billions of years of volcanic activity and biological processes. Early volcanoes released water vapour that condensed into oceans, whilst algae and plants gradually pumped out oxygen through photosynthesis.
Greenhouse gases like carbon dioxide, methane, and water vapour act as Earth's insulating blanket. However, human activities including deforestation, burning fossil fuels, and agriculture have dramatically increased these gases.
This creates serious consequences: melting ice caps, changing rainfall patterns, and shifting storm systems. Your carbon footprint measures how much CO2 and other greenhouse gases you're responsible for throughout your lifetime.
Climate Action: Reducing our carbon footprint through renewable energy, efficient processes, and sustainable choices is crucial for our planet's future!
5
of 5
Using Resources Sustainably
Renewable resources can be replaced as fast as we use them, whilst non-renewable resources can't keep up with our demands. Understanding this difference is crucial for managing Earth's precious materials.
Potable water (safe drinking water) requires careful treatment: fresh water passes through filtration systems, then gets sterilised using chlorine, ozone, or UV light. It sounds simple, but clean water is a luxury many lack!
Life cycle assessment tracks a product's environmental impact from raw material extraction through manufacturing, use, and disposal. Sewage treatment involves screening, settling, aerobic treatment of liquid waste, and anaerobic digestion of solid sludge.
Sustainability Matters: Every product you use has hidden environmental costs - thinking about life cycles helps you make smarter choices for the planet!
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: Properties of Water
2
BiologyProperties of Water
Explore the unique properties of water, including hydrogen bonding, specific heat capacity, cohesion, and its role as a solvent in biological systems. This summary covers key concepts relevant to AQA A-Level Biology and Chemistry, highlighting water's importance in osmoregulation, transport in plants, and metabolic processes.
122022
BiologyEssential Water Properties
Explore the critical functions and unique properties of water, including its role as a solvent, reactant, and temperature regulator. Understand hydrogen bonding, cohesion, and how these characteristics support life in various habitats. This summary covers key concepts essential for biology students.
1243712
Most popular content in Chemistry
9G
ChemistryGCSE AQA Chemistry Topic 1- The Atom
The Atom
101,0260
Chemistrychem paper 1
higher
111,85637
ChemistryA-level OCR A Chemistry summary sheets
Everything from snaprevise for OCR chemistry a-level
122,17678
ChemistryEssential Chemistry Practicals
Explore key AQA GCSE Chemistry practicals, including flame tests, titration, and gas identification. This resource covers essential techniques for analyzing ions, making salts, and understanding reaction kinetics. Perfect for students preparing for exams and practical assessments.
1011,813902
G
ChemistryGCSE AQA Chemistry Topic 1
Quiz covering all of topic 1
101,6723
C
Chemistrychem paper 1
Unlock the secrets of chemical reactions with this comprehensive flashcard set designed to help you conquer complex concepts and ace your Chemistry exams.
116211
A
ChemistryAQA GCSE Chemistry 4.4 Chemical changes
4.4 Reactions of acids with bases or carbonates
95941
F
ChemistryFundamentals of Atomic Structure
Practice identifying subatomic particles, calculating neutrons, and defining isotopes and atomic/mass numbers.
123400
A
ChemistryAtomic Mass and Atomic Number Calculations
Calculate the number of protons, neutrons, and electrons for different elements and isotopes.
S34790
Most popular content
9
SociologySociology 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.
12102,3893,038
CriminologyCriminology: Crime & Punishment Overview
Comprehensive mindmaps covering key concepts in the Crime and Punishment topic for WJEC Criminology Unit 4. This resource includes detailed insights into the Criminal Justice System, crime prevention strategies, sentencing models, and the roles of various agencies. Ideal for A-Level revision, ensuring you grasp essential theories and legislative processes to excel in your exams.
1254,8131,059
SociologySociology 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.
1273,2392,304
English LiteratureAn 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.
1025,231901
CriminologyWJEC Unit 4 Criminology
Criminology unit 4 detailed revision note
127,120124
CriminologyCriminology Theories Overview
Explore key criminology theories and their implications on crime and deviance. This comprehensive summary covers biological, psychological, and sociological perspectives, including labelling theory, right realism, and the impact of social campaigns on policy development. Ideal for A-Level criminology students seeking to understand the complexities of criminal behaviour and the factors influencing crime prevention strategies.
129,746211
English LiteratureRomeo and Juliet: Key themes
Key Romeo and Juliet themes and analysed quotes
106,619197
C
BiologyCell Biology and Cell structure
cell structures
92,6740
English LiteratureMacbeth: 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.
918,834392
Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.6/5App Store
4.7/5Google 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 SiOS 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 KlichAndroid 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.
AnnaiOS user
Chemistry238 views·Updated Jun 2, 2026·5 pagesAQA Combined Science Chemistry Paper 2: Higher Tier
Faye Findlay@fayefindlay_ylvf
Chemistry is all around you - from the air you breathe to the water you drink! This summary covers the essential reactions, compounds, and processes that shape our world, giving you the knowledge you need to ace your chemistry exams.
1
of 5Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
Rate of Reaction & Equilibrium
Ever wondered why some reactions happen instantly whilst others take ages? The rate of reaction measures how quickly reactants transform into products, and it's all about particle collisions.
Collision theory explains that particles must crash into each other with enough energy to create a successful reaction. You can speed things up by increasing temperature (particles move faster), concentration (more particles in the same space), pressure (particles squashed together), or surface area (more exposed reaction sites).
Catalysts are like chemical matchmakers - they speed up reactions without getting used up themselves. Meanwhile, reversible reactions reach equilibrium when the forward and backward reactions happen at the same rate, shown by the ⇌ symbol.
Key Tip: Remember that Le Chatelier's Principle means equilibrium systems always fight back against changes - if you increase pressure, the system shifts to reduce it!
2
of 5Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
Hydrocarbons & Crude Oil
Hydrocarbons are simple compounds made only of carbon and hydrogen atoms, but they power our entire world! The simplest type, alkanes, follow the formula CnH2n+2 - from methane (CH4) to butane (C4H10).
Crude oil is ancient plankton that's been cooking underground for millions of years. We extract this non-renewable treasure through fractional distillation - heating it up so different compounds evaporate at different temperatures.
Longer hydrocarbon chains are thick and less flammable, whilst shorter ones are runny and highly flammable. That's why we use cracking to split long chains into more useful shorter ones and reactive alkenes.
Remember: In fractional distillation, it's hotter at the bottom (longer hydrocarbons) and cooler at the top (shorter hydrocarbons) - think of it like a chemical skyscraper!
3
of 5Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
Purity & Chemical Analysis
Pure substances are chemistry's perfectionists - they contain only one compound or element and melt or boil at exact temperatures. But most useful materials are actually formulations - carefully designed mixtures that do specific jobs perfectly.
Chromatography is your detective tool for separating mixtures. It works using a mobile phase (where molecules can move) and a stationary phase (where they can't), letting you identify mystery substances.
You can also identify gases using simple tests: chlorine turns damp litmus paper white, oxygen relights a glowing splint, and carbon dioxide makes limewater go cloudy.
Pro Tip: The further a substance travels in chromatography, the more soluble it is in the mobile phase - use this to identify unknown compounds!
4
of 5Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
Chemistry of the Atmosphere
Our atmosphere wasn't always perfect for life - it evolved through billions of years of volcanic activity and biological processes. Early volcanoes released water vapour that condensed into oceans, whilst algae and plants gradually pumped out oxygen through photosynthesis.
Greenhouse gases like carbon dioxide, methane, and water vapour act as Earth's insulating blanket. However, human activities including deforestation, burning fossil fuels, and agriculture have dramatically increased these gases.
This creates serious consequences: melting ice caps, changing rainfall patterns, and shifting storm systems. Your carbon footprint measures how much CO2 and other greenhouse gases you're responsible for throughout your lifetime.
Climate Action: Reducing our carbon footprint through renewable energy, efficient processes, and sustainable choices is crucial for our planet's future!
5
of 5Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
Using Resources Sustainably
Renewable resources can be replaced as fast as we use them, whilst non-renewable resources can't keep up with our demands. Understanding this difference is crucial for managing Earth's precious materials.
Potable water (safe drinking water) requires careful treatment: fresh water passes through filtration systems, then gets sterilised using chlorine, ozone, or UV light. It sounds simple, but clean water is a luxury many lack!
Life cycle assessment tracks a product's environmental impact from raw material extraction through manufacturing, use, and disposal. Sewage treatment involves screening, settling, aerobic treatment of liquid waste, and anaerobic digestion of solid sludge.
Sustainability Matters: Every product you use has hidden environmental costs - thinking about life cycles helps you make smarter choices for the planet!
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: Properties of Water
2BiologyProperties of Water
Explore the unique properties of water, including hydrogen bonding, specific heat capacity, cohesion, and its role as a solvent in biological systems. This summary covers key concepts relevant to AQA A-Level Biology and Chemistry, highlighting water's importance in osmoregulation, transport in plants, and metabolic processes.
122022
BiologyEssential Water Properties
Explore the critical functions and unique properties of water, including its role as a solvent, reactant, and temperature regulator. Understand hydrogen bonding, cohesion, and how these characteristics support life in various habitats. This summary covers key concepts essential for biology students.
1243712
Most popular content in Chemistry
9G
ChemistryGCSE AQA Chemistry Topic 1- The Atom
The Atom
101,0260
Chemistrychem paper 1
higher
111,85637
ChemistryA-level OCR A Chemistry summary sheets
Everything from snaprevise for OCR chemistry a-level
122,17678
ChemistryEssential Chemistry Practicals
Explore key AQA GCSE Chemistry practicals, including flame tests, titration, and gas identification. This resource covers essential techniques for analyzing ions, making salts, and understanding reaction kinetics. Perfect for students preparing for exams and practical assessments.
1011,813902
G
ChemistryGCSE AQA Chemistry Topic 1
Quiz covering all of topic 1
101,6723
C
Chemistrychem paper 1
Unlock the secrets of chemical reactions with this comprehensive flashcard set designed to help you conquer complex concepts and ace your Chemistry exams.
116211
A
ChemistryAQA GCSE Chemistry 4.4 Chemical changes
4.4 Reactions of acids with bases or carbonates
95941
F
ChemistryFundamentals of Atomic Structure
Practice identifying subatomic particles, calculating neutrons, and defining isotopes and atomic/mass numbers.
123400
A
ChemistryAtomic Mass and Atomic Number Calculations
Calculate the number of protons, neutrons, and electrons for different elements and isotopes.
S34790
Most popular content
9SociologySociology 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.
12102,3893,038
CriminologyCriminology: Crime & Punishment Overview
Comprehensive mindmaps covering key concepts in the Crime and Punishment topic for WJEC Criminology Unit 4. This resource includes detailed insights into the Criminal Justice System, crime prevention strategies, sentencing models, and the roles of various agencies. Ideal for A-Level revision, ensuring you grasp essential theories and legislative processes to excel in your exams.
1254,8131,059
SociologySociology 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.
1273,2392,304
English LiteratureAn 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.
1025,231901
CriminologyWJEC Unit 4 Criminology
Criminology unit 4 detailed revision note
127,120124
CriminologyCriminology Theories Overview
Explore key criminology theories and their implications on crime and deviance. This comprehensive summary covers biological, psychological, and sociological perspectives, including labelling theory, right realism, and the impact of social campaigns on policy development. Ideal for A-Level criminology students seeking to understand the complexities of criminal behaviour and the factors influencing crime prevention strategies.
129,746211
English LiteratureRomeo and Juliet: Key themes
Key Romeo and Juliet themes and analysed quotes
106,619197
C
BiologyCell Biology and Cell structure
cell structures
92,6740
English LiteratureMacbeth: 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.
918,834392
Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.6/5App Store
4.7/5Google 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 SiOS 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 KlichAndroid 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.
AnnaiOS user