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Chemistry
6 Dec 2025
139
5 pages
sy7 @sy7_quyl
Ever wondered why some chemical reactions happen in a flash whilst others take ages? Understanding how to control... Show more
You already know the four main ways to speed up reactions increase temperature, decrease particle size, increase concentration, and use a catalyst. These aren't just random facts - they're essential tools that industrial chemists use every day.
Collision theory explains why these methods work. Simply put, particles must crash into each other before any reaction can happen. The more collisions you get, the faster your reaction goes.
When you increase surface area by grinding up particles, you're giving more space for collisions to occur. Think of it like this a whole sugar cube dissolves slowly, but granulated sugar disappears instantly because there's loads more surface exposed to the water.
Quick Check Powdered magnesium reacts much faster with acid than magnesium ribbon because there are far more collision sites available.
Here's where chemistry gets practical - you can actually measure how fast reactions go by tracking volume changes over time. The data shows that ground chips (S) produce gas much faster than whole chips (L).
Looking at the numbers, ground chips had an average rate of 1.8 cm³/s in the first 20 seconds, whilst whole chips only managed 1.3 cm³/s. That's collision theory in action right there.
Notice how both reactions slow down over time? The ground chips dropped to just 0.2 cm³/s in the second interval whilst whole chips fell to 0.72 cm³/s. This happens because you're running out of reactants to collide.
Pro Tip Always plot your results on a graph - it makes patterns much clearer than staring at tables of numbers.
Method B tracks the reaction by measuring mass loss instead of gas volume. The pattern's identical though - smaller particles react faster because there's more surface area for collisions.
Ground chips lost mass at 0.068 g/s initially, compared to 0.05 g/s for whole chips. By the second 20-second period, the ground chips had practically stopped reacting whilst whole chips were still going at 0.018 g/s.
This shows you something important particle size doesn't just affect how fast a reaction starts - it completely changes the reaction profile. Smaller particles burn through reactants quickly then stop, whilst larger ones have a steadier, longer-lasting reaction.
Real World This is why different grain sizes of gunpowder create different explosive effects in fireworks.
Concentration affects reaction rates because more particles in the same space means more collisions. It's like a busy dance floor - the more crowded it gets, the more people bump into each other.
As reactions progress, they naturally slow down because you're converting reactants into products. Fewer reactant particles means fewer collisions, which means a slower rate. The graph always curves downwards for this reason.
You can calculate relative rate using the formula 1/time, which gives you the rate at one specific moment. This is different from average rate, which looks at change over a time period. Relative rate has units of s⁻¹, whilst average rate units depend on what you're measuring.
Exam Tip Remember that relative rate = 1/time is only valid when comparing reactions that go to the same extent of completion.
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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Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Explore key concepts in A Level Chemistry Module 3, focusing on periodic trends, ionization energy, enthalpy changes, and reaction kinetics. This summary covers essential topics such as group 7 elements, shielding effects, and dynamic equilibrium, providing a comprehensive overview for students preparing for exams. Ideal for quick revision and understanding of chemical bonding and energy changes.
ChemistryExplore the fundamentals of chemical reaction rates, including the collision theory and five key factors that influence reaction speed. This summary covers essential concepts for National 5 Chemistry, making it a valuable resource for understanding reaction kinetics and the rate of chemical change.
ChemistryExplore the fundamentals of reaction rates in this detailed summary, covering key concepts such as rate laws, rate-determining steps, and the Arrhenius equation. Ideal for OCR A A-Level Chemistry students, this resource provides insights into zero, first, and second-order reactions, along with graphical representations and calculations of rate constants. Enhance your understanding of reaction kinetics and improve your exam preparation.
ChemistryExplore detailed mechanisms of organic reactions including nucleophilic substitution, radical substitution, and electrophilic addition. This summary covers key concepts such as alkenes, aromatic compounds, and carboxylic acids, providing essential insights for A-Level organic chemistry students.
ChemistryExplore the relationship between temperature and the rate of reaction in the sodium thiosulfate and hydrochloric acid experiment. This practical investigation covers key concepts in kinetics, including collision theory and the impact of temperature on reaction rates. Ideal for students studying chemical kinetics and reaction mechanisms.
ChemistryExplore essential techniques in chemical analysis, including volumetric analysis (titration), chromatography (paper and gas), and their applications in determining substance concentrations. Understand key concepts like retention time, mobile and stationary phases, and indicators in titrations. This summary is ideal for Higher Chemistry students seeking to master chemical analysis methods.
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
sy7
@sy7_quyl
Ever wondered why some chemical reactions happen in a flash whilst others take ages? Understanding how to control reaction rates is crucial for chemists - they need reactions fast enough to be profitable but not so quick they become dangerous... Show more
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You already know the four main ways to speed up reactions: increase temperature, decrease particle size, increase concentration, and use a catalyst. These aren't just random facts - they're essential tools that industrial chemists use every day.
Collision theory explains why these methods work. Simply put, particles must crash into each other before any reaction can happen. The more collisions you get, the faster your reaction goes.
When you increase surface area by grinding up particles, you're giving more space for collisions to occur. Think of it like this: a whole sugar cube dissolves slowly, but granulated sugar disappears instantly because there's loads more surface exposed to the water.
Quick Check: Powdered magnesium reacts much faster with acid than magnesium ribbon because there are far more collision sites available.
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Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Here's where chemistry gets practical - you can actually measure how fast reactions go by tracking volume changes over time. The data shows that ground chips (S) produce gas much faster than whole chips (L).
Looking at the numbers, ground chips had an average rate of 1.8 cm³/s in the first 20 seconds, whilst whole chips only managed 1.3 cm³/s. That's collision theory in action right there.
Notice how both reactions slow down over time? The ground chips dropped to just 0.2 cm³/s in the second interval whilst whole chips fell to 0.72 cm³/s. This happens because you're running out of reactants to collide.
Pro Tip: Always plot your results on a graph - it makes patterns much clearer than staring at tables of numbers.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Method B tracks the reaction by measuring mass loss instead of gas volume. The pattern's identical though - smaller particles react faster because there's more surface area for collisions.
Ground chips lost mass at 0.068 g/s initially, compared to 0.05 g/s for whole chips. By the second 20-second period, the ground chips had practically stopped reacting whilst whole chips were still going at 0.018 g/s.
This shows you something important: particle size doesn't just affect how fast a reaction starts - it completely changes the reaction profile. Smaller particles burn through reactants quickly then stop, whilst larger ones have a steadier, longer-lasting reaction.
Real World: This is why different grain sizes of gunpowder create different explosive effects in fireworks.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Concentration affects reaction rates because more particles in the same space means more collisions. It's like a busy dance floor - the more crowded it gets, the more people bump into each other.
As reactions progress, they naturally slow down because you're converting reactants into products. Fewer reactant particles means fewer collisions, which means a slower rate. The graph always curves downwards for this reason.
You can calculate relative rate using the formula 1/time, which gives you the rate at one specific moment. This is different from average rate, which looks at change over a time period. Relative rate has units of s⁻¹, whilst average rate units depend on what you're measuring.
Exam Tip: Remember that relative rate = 1/time is only valid when comparing reactions that go to the same extent of completion.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
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.
0
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Explore key concepts in A Level Chemistry Module 3, focusing on periodic trends, ionization energy, enthalpy changes, and reaction kinetics. This summary covers essential topics such as group 7 elements, shielding effects, and dynamic equilibrium, providing a comprehensive overview for students preparing for exams. Ideal for quick revision and understanding of chemical bonding and energy changes.
ChemistryExplore the fundamentals of chemical reaction rates, including the collision theory and five key factors that influence reaction speed. This summary covers essential concepts for National 5 Chemistry, making it a valuable resource for understanding reaction kinetics and the rate of chemical change.
ChemistryExplore the fundamentals of reaction rates in this detailed summary, covering key concepts such as rate laws, rate-determining steps, and the Arrhenius equation. Ideal for OCR A A-Level Chemistry students, this resource provides insights into zero, first, and second-order reactions, along with graphical representations and calculations of rate constants. Enhance your understanding of reaction kinetics and improve your exam preparation.
ChemistryExplore detailed mechanisms of organic reactions including nucleophilic substitution, radical substitution, and electrophilic addition. This summary covers key concepts such as alkenes, aromatic compounds, and carboxylic acids, providing essential insights for A-Level organic chemistry students.
ChemistryExplore the relationship between temperature and the rate of reaction in the sodium thiosulfate and hydrochloric acid experiment. This practical investigation covers key concepts in kinetics, including collision theory and the impact of temperature on reaction rates. Ideal for students studying chemical kinetics and reaction mechanisms.
ChemistryExplore essential techniques in chemical analysis, including volumetric analysis (titration), chromatography (paper and gas), and their applications in determining substance concentrations. Understand key concepts like retention time, mobile and stationary phases, and indicators in titrations. This summary is ideal for Higher Chemistry students seeking to master chemical analysis methods.
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