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Module 3 energetics
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29 Jan 2023
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A Level OCR Chemistry Energetics Module 3: Study Notes and Questions
Emma Corden
@emmacorden_rpll
Calorimetry and Hess's Law
This page delves into practical methods for measuring enthalpy changes through calorimetry and introduces Hess's Law for calculating enthalpy changes indirectly.
The fundamental equation for calorimetry is presented:
Definition: Energy transferred = mass × specific heat capacity × change in temperature
A detailed method for calorimetry using a spirit burner is outlined, including steps for measuring initial and final temperatures and masses.
Example: To calculate enthalpy change in kJ mol^-1, divide the energy transferred to water by the number of moles of fuel burned.
The limitations of experimental enthalpy change calculations are discussed, including high activation energies, slow reaction rates, and multiple simultaneous reactions.
Hess's Law is introduced as a crucial concept for indirect enthalpy calculations:
Definition: Hess's Law states that if a reaction can occur through multiple routes with the same initial and final conditions, the total enthalpy change remains constant.
Potential sources of error in calorimetry experiments are identified:
- Energy loss to surroundings
- Incomplete combustion
- Non-standard conditions
The page concludes with equations for calculating enthalpy changes using Hess's Law for combustion reactions.
Bond Enthalpies and Formation Reactions
This final page focuses on formation reactions, bond breaking and making processes, and the concept of average bond enthalpies.
The relationship between enthalpy of formation and enthalpy of reaction is explained through equations.
Highlight: The enthalpy of formation for any element in its standard state is always zero.
The energetics of bond breaking and bond making are discussed:
Definition: Bond breaking is an endothermic process that requires energy, while bond making is an exothermic process that releases energy.
The concept of average bond enthalpy is introduced:
Definition: Average bond enthalpy is the energy required to break one mole of a specific covalent bond, averaged over a range of compounds, measured in kJ mol^-1.
Highlight: Bond breaking is always endothermic, while bond making is always exothermic.
The limitations of using average bond enthalpies are noted:
Example: The actual bond enthalpy in a specific molecule can vary from the average value used in calculations.
The page concludes with the equation for calculating overall enthalpy change using bond enthalpies:
Definition: Overall enthalpy change = Sum of energies for bonds broken - Sum of energies for bonds made
This comprehensive guide provides A level OCR chemistry energetics module 3 study notes and questions, covering essential concepts and practical applications for OCR A level Chemistry module 3 exam questions.
Energy Level Diagrams and Enthalpy Changes
This page introduces fundamental concepts in energetics, focusing on energy level diagrams and various types of enthalpy changes.
Energy level diagrams are used to visualize the energy changes in chemical reactions. These diagrams show the activation energy, overall energy change, and whether a reaction is exothermic or endothermic.
Definition: Enthalpy is the energy stored in chemical bonds.
Exothermic and endothermic reactions are differentiated based on their energy changes:
Example: Exothermic reactions, such as acid reacting with hydrogencarbonate, release energy to the surroundings, causing the temperature to increase.
Example: Endothermic reactions, like thermal decomposition, absorb energy from the surroundings, resulting in a temperature decrease.
The concept of activation energy is introduced:
Definition: Activation energy is the minimum energy that particles must possess to collide and react, measured in kJ mol^-1.
Standard enthalpy changes are defined under specific conditions:
Highlight: Standard conditions are defined as 100 kPa pressure, 298 K temperature, and 1 mol dm^-3 concentration.
Various types of standard enthalpy changes are explained:
- Standard enthalpy change of reaction
- Standard enthalpy change of formation
- Standard enthalpy change of combustion
- Standard enthalpy change of neutralization
Vocabulary: Standard enthalpy change of formation is the enthalpy change associated with forming 1 mole of a compound from its elements under standard conditions, with all substances in their standard states.
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Anna
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Best app on earth! no words because it’s too good
Thomas R
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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
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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
A Level OCR Chemistry Energetics Module 3: Study Notes and Questions
Emma Corden
@emmacorden_rpll
A Level OCR Chemistry Energetics Module 3 Study Notes and Questions
This comprehensive guide covers key concepts in energetics for OCR A Level Chemistry Module 3, including energy level diagrams, enthalpy changes, calorimetry, and bond enthalpies. It provides detailed explanations,... Show more
Calorimetry and Hess's Law
This page delves into practical methods for measuring enthalpy changes through calorimetry and introduces Hess's Law for calculating enthalpy changes indirectly.
The fundamental equation for calorimetry is presented:
Definition: Energy transferred = mass × specific heat capacity × change in temperature
A detailed method for calorimetry using a spirit burner is outlined, including steps for measuring initial and final temperatures and masses.
Example: To calculate enthalpy change in kJ mol^-1, divide the energy transferred to water by the number of moles of fuel burned.
The limitations of experimental enthalpy change calculations are discussed, including high activation energies, slow reaction rates, and multiple simultaneous reactions.
Hess's Law is introduced as a crucial concept for indirect enthalpy calculations:
Definition: Hess's Law states that if a reaction can occur through multiple routes with the same initial and final conditions, the total enthalpy change remains constant.
Potential sources of error in calorimetry experiments are identified:
- Energy loss to surroundings
- Incomplete combustion
- Non-standard conditions
The page concludes with equations for calculating enthalpy changes using Hess's Law for combustion reactions.
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Bond Enthalpies and Formation Reactions
This final page focuses on formation reactions, bond breaking and making processes, and the concept of average bond enthalpies.
The relationship between enthalpy of formation and enthalpy of reaction is explained through equations.
Highlight: The enthalpy of formation for any element in its standard state is always zero.
The energetics of bond breaking and bond making are discussed:
Definition: Bond breaking is an endothermic process that requires energy, while bond making is an exothermic process that releases energy.
The concept of average bond enthalpy is introduced:
Definition: Average bond enthalpy is the energy required to break one mole of a specific covalent bond, averaged over a range of compounds, measured in kJ mol^-1.
Highlight: Bond breaking is always endothermic, while bond making is always exothermic.
The limitations of using average bond enthalpies are noted:
Example: The actual bond enthalpy in a specific molecule can vary from the average value used in calculations.
The page concludes with the equation for calculating overall enthalpy change using bond enthalpies:
Definition: Overall enthalpy change = Sum of energies for bonds broken - Sum of energies for bonds made
This comprehensive guide provides A level OCR chemistry energetics module 3 study notes and questions, covering essential concepts and practical applications for OCR A level Chemistry module 3 exam questions.
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
Energy Level Diagrams and Enthalpy Changes
This page introduces fundamental concepts in energetics, focusing on energy level diagrams and various types of enthalpy changes.
Energy level diagrams are used to visualize the energy changes in chemical reactions. These diagrams show the activation energy, overall energy change, and whether a reaction is exothermic or endothermic.
Definition: Enthalpy is the energy stored in chemical bonds.
Exothermic and endothermic reactions are differentiated based on their energy changes:
Example: Exothermic reactions, such as acid reacting with hydrogencarbonate, release energy to the surroundings, causing the temperature to increase.
Example: Endothermic reactions, like thermal decomposition, absorb energy from the surroundings, resulting in a temperature decrease.
The concept of activation energy is introduced:
Definition: Activation energy is the minimum energy that particles must possess to collide and react, measured in kJ mol^-1.
Standard enthalpy changes are defined under specific conditions:
Highlight: Standard conditions are defined as 100 kPa pressure, 298 K temperature, and 1 mol dm^-3 concentration.
Various types of standard enthalpy changes are explained:
- Standard enthalpy change of reaction
- Standard enthalpy change of formation
- Standard enthalpy change of combustion
- Standard enthalpy change of neutralization
Vocabulary: Standard enthalpy change of formation is the enthalpy change associated with forming 1 mole of a compound from its elements under standard conditions, with all substances in their standard states.
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.
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
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