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Dec 27, 2025
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Comprehensive AP Chemistry Study Guides for Units 3-5
Violet P
@ruta_sepepsi
1 / 3
Intermolecular Forces and States of Matter
Ever wonder why some substances are solid at room temperature while others are gases? It all comes down to intermolecular forces (IMFs). These attractive forces between molecules determine physical properties like melting point, boiling point, and solubility.
Different types of substances have different IMFs. Ionic compounds have strong attractions between ions, making them brittle with high melting points. Molecular compounds have weaker forces between molecules, resulting in lower melting points. Metallic substances contain delocalized electrons that allow them to conduct electricity and be malleable.
For molecular substances, the strength of attraction varies: hydrogen bonding (between H and N, O, or F) is strongest, followed by dipole-dipole forces (between polar molecules), and finally temporary dipoles (present in all molecules). Remember that stronger IMFs mean higher melting/boiling points and lower vapor pressures.
💡 The Ideal Gas Law helps predict gas behavior, but real gases deviate at high pressures and low temperatures because IMFs become more significant!
Gas behavior depends on molecular motion and kinetic energy. Heavier gas molecules move slower than lighter ones at the same temperature since kinetic energy remains constant at a given temperature.
In chromatography, we separate substances based on their attractions to stationary and mobile phases. The retention factor (Rf) tells us how far a compound travels relative to the solvent. Remember: "like dissolves like" - polar substances dissolve better in polar solvents like water.
Chemical Reactions and Stoichiometry
Chemical reactions create new substances by breaking and forming bonds, unlike physical changes that just break IMFs. When writing ionic equations, remember to separate aqueous compounds into ions while keeping solids, liquids, and gases intact.
There are three ways to write chemical equations:
- Molecular equations show the complete formulas
- Complete ionic equations separate aqueous compounds into ions
- Net ionic equations eliminate spectator ions that don't participate in the reaction
Stoichiometry is your tool for calculating quantities in chemical reactions. The limiting reactant determines the theoretical yield because it's completely consumed first. Calculate percent yield by dividing actual yield by theoretical yield and multiplying by 100.
🧪 In acid-base reactions, acids donate H⁺ ions while bases accept them. When an acid reacts, it forms its conjugate base; when a base reacts, it forms its conjugate acid.
Redox reactions involve the transfer of electrons, with oxidation (losing electrons) and reduction (gaining electrons) occurring simultaneously. To identify what's being oxidized or reduced, track oxidation numbers using these rules:
- Free elements = 0
- Group 1 elements = +1 in compounds
- Group 2 elements = +2 in compounds
- Fluorine = -1 in compounds
- Hydrogen = +1 with non-metals, -1 with metals
- Oxygen usually = -2
Remember those diatomic molecules (Br₂, I₂, N₂, Cl₂, H₂, O₂, F₂) and polyatomic ions like sulfate (SO₄²⁻), nitrate (NO₃⁻), and ammonium (NH₄⁺) for writing correct formulas in reactions.
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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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I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
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Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
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
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
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 app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
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
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
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
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
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 app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
Paul T
iOS user
Comprehensive AP Chemistry Study Guides for Units 3-5
Violet P
@ruta_sepepsi
Welcome to your guide to AP Chemistry Units 3 and 4! These units cover intermolecular forces, gas laws, and chemical reactions. Understanding these concepts is crucial for explaining how substances behave and interact at both molecular and macroscopic levels.
Intermolecular Forces and States of Matter
Ever wonder why some substances are solid at room temperature while others are gases? It all comes down to intermolecular forces (IMFs). These attractive forces between molecules determine physical properties like melting point, boiling point, and solubility.
Different types of substances have different IMFs. Ionic compounds have strong attractions between ions, making them brittle with high melting points. Molecular compounds have weaker forces between molecules, resulting in lower melting points. Metallic substances contain delocalized electrons that allow them to conduct electricity and be malleable.
For molecular substances, the strength of attraction varies: hydrogen bonding (between H and N, O, or F) is strongest, followed by dipole-dipole forces (between polar molecules), and finally temporary dipoles (present in all molecules). Remember that stronger IMFs mean higher melting/boiling points and lower vapor pressures.
💡 The Ideal Gas Law helps predict gas behavior, but real gases deviate at high pressures and low temperatures because IMFs become more significant!
Gas behavior depends on molecular motion and kinetic energy. Heavier gas molecules move slower than lighter ones at the same temperature since kinetic energy remains constant at a given temperature.
In chromatography, we separate substances based on their attractions to stationary and mobile phases. The retention factor (Rf) tells us how far a compound travels relative to the solvent. Remember: "like dissolves like" - polar substances dissolve better in polar solvents like water.
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Chemical Reactions and Stoichiometry
Chemical reactions create new substances by breaking and forming bonds, unlike physical changes that just break IMFs. When writing ionic equations, remember to separate aqueous compounds into ions while keeping solids, liquids, and gases intact.
There are three ways to write chemical equations:
- Molecular equations show the complete formulas
- Complete ionic equations separate aqueous compounds into ions
- Net ionic equations eliminate spectator ions that don't participate in the reaction
Stoichiometry is your tool for calculating quantities in chemical reactions. The limiting reactant determines the theoretical yield because it's completely consumed first. Calculate percent yield by dividing actual yield by theoretical yield and multiplying by 100.
🧪 In acid-base reactions, acids donate H⁺ ions while bases accept them. When an acid reacts, it forms its conjugate base; when a base reacts, it forms its conjugate acid.
Redox reactions involve the transfer of electrons, with oxidation (losing electrons) and reduction (gaining electrons) occurring simultaneously. To identify what's being oxidized or reduced, track oxidation numbers using these rules:
- Free elements = 0
- Group 1 elements = +1 in compounds
- Group 2 elements = +2 in compounds
- Fluorine = -1 in compounds
- Hydrogen = +1 with non-metals, -1 with metals
- Oxygen usually = -2
Remember those diatomic molecules (Br₂, I₂, N₂, Cl₂, H₂, O₂, F₂) and polyatomic ions like sulfate (SO₄²⁻), nitrate (NO₃⁻), and ammonium (NH₄⁺) for writing correct formulas in reactions.
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We thought you’d never ask...
What is the Knowunity AI companion?
Our AI companion is specifically built for the needs of students. Based on the millions of content pieces we have on the platform we can provide truly meaningful and relevant answers to students. But its not only about answers, the companion is even more about guiding students through their daily learning challenges, with personalised study plans, quizzes or content pieces in the chat and 100% personalisation based on the students skills and developments.
Where can I download the Knowunity app?
You can download the app in the Google Play Store and in the 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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4.9/5
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4.8/5
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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
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
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
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
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 app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
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
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
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
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
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 app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
Paul T
iOS user