Subjects
Classic Dramatic Literature
Modern Lyric Poetry
Influential English-Language Authors
Classic and Contemporary Novels
Literary Character Analysis
Romantic and Love Poetry
Reading Analysis and Interpretation
Evidence Analysis and Integration
Author's Stylistic Elements
Figurative Language and Rhetoric
Show all topics
Human Organ Systems
Cellular Organization and Development
Biomolecular Structure and Organization
Enzyme Structure and Regulation
Cellular Organization Types
Biological Homeostatic Processes
Cellular Membrane Structure
Autotrophic Energy Processes
Environmental Sustainability and Impact
Neural Communication Systems
Show all topics
Social Sciences Research & Practice
Social Structure and Mobility
Classic Social Influence Experiments
Social Systems Theories
Family and Relationship Dynamics
Memory Systems and Processes
Neural Bases of Behavior
Social Influence and Attraction
Psychotherapeutic Approaches
Human Agency and Responsibility
Show all topics
Chemical Sciences and Applications
Chemical Bond Types and Properties
Organic Functional Groups
Atomic Structure and Composition
Chromatographic Separation Principles
Chemical Compound Classifications
Electrochemical Cell Systems
Periodic Table Organization
Chemical Reaction Kinetics
Chemical Equation Conservation
Show all topics
Nazi Germany and Holocaust 1933-1945
World Wars and Peace Treaties
European Monarchs and Statesmen
Cold War Global Tensions
Medieval Institutions and Systems
European Renaissance and Enlightenment
Modern Global Environmental-Health Challenges
Modern Military Conflicts
Medieval Migration and Invasions
World Wars Era and Impact
Show all topics
82
•
11 Feb 2026
•
Aarna
@yours_aarna110
Fuel cells and electrolysis are two important electrochemical processes that... Show more
Ever wondered how cars might run without petrol in the future? Fuel cells are the answer - they're like batteries that never run flat because they constantly produce electricity from hydrogen and oxygen. The process is brilliantly simple: fuel gets oxidised, creating a voltage that powers whatever you've connected to it.
The best part about fuel cells is their high efficiency and minimal pollution compared to burning fossil fuels. They're also compact, lightweight, and incredibly reliable - perfect for everything from cars to smartphones.
However, there's a catch. The expensive catalysts needed make them costly to manufacture, and we simply don't have enough hydrogen filling stations yet. Most fuel cell technology is still being tested, and producing hydrogen itself is both expensive and complicated.
💡 Quick Fact: Fuel cells are essentially the opposite of electrolysis - they combine substances to make electricity instead of using electricity to split them apart.
Here's the clever bit: hydrogen fuel cells produce electricity with water as the only waste product - no nasty emissions whatsoever! Understanding the chemistry behind this will help you ace those exam questions.
At the anode (negative terminal), hydrogen gas gets split up: 2H₂ → 4H⁺ + 4e⁻. Meanwhile, at the cathode (positive terminal), oxygen combines with the hydrogen ions and electrons: O₂ + 4H⁺ + 4e⁻ → 2H₂O. The overall reaction is beautifully simple: 2H₂ + O₂ → 2H₂O.
For exam answers about how fuel cells work, remember this sequence: fuel enters the cell, gets oxidised, and sets up a potential difference across the wire. This potential difference is what drives the electrical current that powers your device.
💡 Exam Tip: Always mention that oxidation creates the potential difference - examiners love to see you understand the connection between chemistry and electricity.
Think of electrolysis as using electricity to force chemical reactions that wouldn't normally happen. It's like being a chemical referee - you're splitting up compounds that would rather stay together!
The setup involves two electrodes (anode and cathode) dipped into an electrolyte - that's just a fancy name for a liquid containing ions that can move freely. The power supply drives electrons through the circuit, forcing reactions at both electrodes.
Here's what you need to remember: the cathode (negative electrode) attracts positive ions and reduces them, whilst the anode (positive electrode) attracts negative ions and oxidises them. For example, lead ions (Pb²⁺) get reduced to lead metal at the cathode, whilst bromide ions (Br⁻) get oxidised to bromine gas at the anode.
The reactivity series determines which ions get discharged first - hydrogen ions are quite reactive, so they often get discharged instead of more reactive metal ions like potassium or sodium.
💡 Memory Trick: "An Ox, Red Cat" - Anode Oxidation, Reduction Cathode. This will never let you down in exams!
Getting confused about which ions go where? These electrode rules will sort you out and guarantee marks in your exams.
Anode rules are straightforward: this positive electrode attracts negative ions from compounds, plus hydroxide ions from any aqueous solutions. If you've got a halide present (that's any Group 7 element like chlorine or bromine), it'll probably get discharged here. If there's no halide around, the hydroxide ions will get discharged instead.
These rules might seem like just memorisation, but they're actually predicting real chemical behaviour. Understanding why certain ions prefer certain electrodes will help you tackle any electrolysis question with confidence.
💡 Exam Strategy: Always check if halides are present first - they're usually the ones that get discharged at the anode over hydroxide ions.
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.
App 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 Knowunity AI. 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 Knowunity AI. 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
Aarna
@yours_aarna110
Fuel cells and electrolysis are two important electrochemical processes that work in opposite ways. Fuel cells generate electricity by combining hydrogen and oxygen, whilst electrolysis uses electricity to split compounds apart.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Ever wondered how cars might run without petrol in the future? Fuel cells are the answer - they're like batteries that never run flat because they constantly produce electricity from hydrogen and oxygen. The process is brilliantly simple: fuel gets oxidised, creating a voltage that powers whatever you've connected to it.
The best part about fuel cells is their high efficiency and minimal pollution compared to burning fossil fuels. They're also compact, lightweight, and incredibly reliable - perfect for everything from cars to smartphones.
However, there's a catch. The expensive catalysts needed make them costly to manufacture, and we simply don't have enough hydrogen filling stations yet. Most fuel cell technology is still being tested, and producing hydrogen itself is both expensive and complicated.
💡 Quick Fact: Fuel cells are essentially the opposite of electrolysis - they combine substances to make electricity instead of using electricity to split them apart.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Here's the clever bit: hydrogen fuel cells produce electricity with water as the only waste product - no nasty emissions whatsoever! Understanding the chemistry behind this will help you ace those exam questions.
At the anode (negative terminal), hydrogen gas gets split up: 2H₂ → 4H⁺ + 4e⁻. Meanwhile, at the cathode (positive terminal), oxygen combines with the hydrogen ions and electrons: O₂ + 4H⁺ + 4e⁻ → 2H₂O. The overall reaction is beautifully simple: 2H₂ + O₂ → 2H₂O.
For exam answers about how fuel cells work, remember this sequence: fuel enters the cell, gets oxidised, and sets up a potential difference across the wire. This potential difference is what drives the electrical current that powers your device.
💡 Exam Tip: Always mention that oxidation creates the potential difference - examiners love to see you understand the connection between chemistry and electricity.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Think of electrolysis as using electricity to force chemical reactions that wouldn't normally happen. It's like being a chemical referee - you're splitting up compounds that would rather stay together!
The setup involves two electrodes (anode and cathode) dipped into an electrolyte - that's just a fancy name for a liquid containing ions that can move freely. The power supply drives electrons through the circuit, forcing reactions at both electrodes.
Here's what you need to remember: the cathode (negative electrode) attracts positive ions and reduces them, whilst the anode (positive electrode) attracts negative ions and oxidises them. For example, lead ions (Pb²⁺) get reduced to lead metal at the cathode, whilst bromide ions (Br⁻) get oxidised to bromine gas at the anode.
The reactivity series determines which ions get discharged first - hydrogen ions are quite reactive, so they often get discharged instead of more reactive metal ions like potassium or sodium.
💡 Memory Trick: "An Ox, Red Cat" - Anode Oxidation, Reduction Cathode. This will never let you down in exams!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Getting confused about which ions go where? These electrode rules will sort you out and guarantee marks in your exams.
Anode rules are straightforward: this positive electrode attracts negative ions from compounds, plus hydroxide ions from any aqueous solutions. If you've got a halide present (that's any Group 7 element like chlorine or bromine), it'll probably get discharged here. If there's no halide around, the hydroxide ions will get discharged instead.
These rules might seem like just memorisation, but they're actually predicting real chemical behaviour. Understanding why certain ions prefer certain electrodes will help you tackle any electrolysis question with confidence.
💡 Exam Strategy: Always check if halides are present first - they're usually the ones that get discharged at the anode over hydroxide ions.
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.
1
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
App 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 Knowunity AI. 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 Knowunity AI. 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
Chemistry
English Literature
Sociology
Biology