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1
0
M
Maya Ahad
03/12/2025
Chemistry
EXOTHERMIC AND ENDOTHERMIC
47
•
3 Dec 2025
•
Understanding Exothermic and Endothermic Reactions
M
Maya Ahad
@mayaahad
1 / 3
Energy Transfer in Reactions
Here's something brilliant about the universe - energy is always conserved during chemical reactions. The total amount of energy before and after a reaction stays exactly the same, it just moves around.
When a reaction transfers energy to its surroundings, the product molecules end up with less energy than the reactants. Think of it like this - the "missing" energy hasn't disappeared, it's escaped into the surroundings as heat.
Exothermic reactions are the heat-givers. They transfer energy to the surroundings, making everything around them warmer. Remember: exothermic means energy "exits" the reaction. You'll see this in combustion, oxidation reactions, and neutralisation.
Endothermic reactions do the opposite - they're energy takers. They absorb energy from the surroundings, making things cooler. Think "endothermic = energy enters" the reaction. Thermal decomposition and some fizzy reactions work this way.
Real-world tip: Self-heating coffee cans use exothermic reactions, whilst sports injury ice packs rely on endothermic ones!
Reaction Profiles
Reaction profiles are like energy maps that show what happens during chemical reactions. They're dead useful for understanding why some reactions need a kick-start whilst others happen easily.
The most important concept here is activation energy - this is the minimum energy that particles need to actually react when they collide. Think of it as the energy hill that reactants must climb before they can transform into products.
You can instantly tell if a reaction is exothermic or endothermic by looking at the energy levels. In exothermic reactions, products sit lower than reactants on the energy scale because energy has been released. For endothermic reactions, it's the opposite - products are higher because they've absorbed energy.
These profiles show you three key things: how much energy reactants and products have, the activation energy barrier, and the overall energy change. Once you can read these diagrams, predicting reaction behaviour becomes much easier.
Exam tip: If products are lower than reactants on the profile, it's exothermic. Higher means endothermic!
Calculating Energy Changes
Understanding bond energies is your key to predicting whether reactions will heat up or cool down. Every chemical reaction involves two main energy steps that you need to master.
First, energy must be supplied to break the bonds in reactants - this always requires energy input. Then, when new bonds form in the products, energy gets released. The balance between these two steps determines the overall energy change.
Here's the magic formula: Energy change = Energy needed to break bonds - Energy released forming bonds. If your answer is negative, you've got an exothermic reaction. A positive answer means endothermic.
This calculation method lets you predict reaction behaviour before you even do the experiment. It's particularly handy for working out whether a reaction will be useful for heating or cooling applications.
Calculation reminder: Negative result = exothermic (energy released), Positive result = endothermic (energy absorbed)!
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Stefan S
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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
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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
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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
Understanding Exothermic and Endothermic Reactions
M
Maya Ahad
@mayaahad
Ever wondered why some reactions make things hot whilst others cool them down? Energy changes in chemical reactions are happening all around you - from the warmth of hand warmers to the cooling effect of sports injury packs. Understanding how... Show more
Energy Transfer in Reactions
Here's something brilliant about the universe - energy is always conserved during chemical reactions. The total amount of energy before and after a reaction stays exactly the same, it just moves around.
When a reaction transfers energy to its surroundings, the product molecules end up with less energy than the reactants. Think of it like this - the "missing" energy hasn't disappeared, it's escaped into the surroundings as heat.
Exothermic reactions are the heat-givers. They transfer energy to the surroundings, making everything around them warmer. Remember: exothermic means energy "exits" the reaction. You'll see this in combustion, oxidation reactions, and neutralisation.
Endothermic reactions do the opposite - they're energy takers. They absorb energy from the surroundings, making things cooler. Think "endothermic = energy enters" the reaction. Thermal decomposition and some fizzy reactions work this way.
Real-world tip: Self-heating coffee cans use exothermic reactions, whilst sports injury ice packs rely on endothermic ones!
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Reaction Profiles
Reaction profiles are like energy maps that show what happens during chemical reactions. They're dead useful for understanding why some reactions need a kick-start whilst others happen easily.
The most important concept here is activation energy - this is the minimum energy that particles need to actually react when they collide. Think of it as the energy hill that reactants must climb before they can transform into products.
You can instantly tell if a reaction is exothermic or endothermic by looking at the energy levels. In exothermic reactions, products sit lower than reactants on the energy scale because energy has been released. For endothermic reactions, it's the opposite - products are higher because they've absorbed energy.
These profiles show you three key things: how much energy reactants and products have, the activation energy barrier, and the overall energy change. Once you can read these diagrams, predicting reaction behaviour becomes much easier.
Exam tip: If products are lower than reactants on the profile, it's exothermic. Higher means endothermic!
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
Calculating Energy Changes
Understanding bond energies is your key to predicting whether reactions will heat up or cool down. Every chemical reaction involves two main energy steps that you need to master.
First, energy must be supplied to break the bonds in reactants - this always requires energy input. Then, when new bonds form in the products, energy gets released. The balance between these two steps determines the overall energy change.
Here's the magic formula: Energy change = Energy needed to break bonds - Energy released forming bonds. If your answer is negative, you've got an exothermic reaction. A positive answer means endothermic.
This calculation method lets you predict reaction behaviour before you even do the experiment. It's particularly handy for working out whether a reaction will be useful for heating or cooling applications.
Calculation reminder: Negative result = exothermic (energy released), Positive result = endothermic (energy absorbed)!
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.
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Most popular content: Exothermic Process
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Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.9/5
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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