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Classification of Matter & Atomic Structure
Ever wonder what everything around you is actually made of? All matter falls into either pure substances (elements and compounds) or mixtures (homogeneous or heterogeneous). We separate mixtures using different methods based on their properties: distillation for different boiling points, chromatography for varying molecular polarity, and filtration for different particle sizes.
Atoms are the building blocks of everything! To understand them, remember that atomic mass - atomic number = number of neutrons. When electrons move between energy levels in atoms, they release energy as light, creating distinctive bright line spectra that act like atomic fingerprints.
The periodic table organizes elements logically, with metals on the left (good conductors, malleable, low electronegativity) and nonmetals on the right (poor conductors, brittle, high electronegativity). As you move across a period, electronegativity and ionization energy increase, while moving down a group decreases both.
Quick Tip: Remember that some elements exist in different forms called allotropes - like carbon appearing as both diamonds and graphite - same element, completely different properties!
Understanding bonds between atoms is crucial. Covalent bonds share electrons between nonmetals, creating compounds with low melting points that don't conduct electricity. Ionic bonds transfer electrons (like in Ca(NO₃)₂), forming strong compounds with high melting points that conduct electricity when dissolved or melted.
Chemical Language & Reactions
Chemical formulas are like recipes that tell you exactly what's in a compound. Molecular formulas show the actual number of atoms (like H₂O), while empirical formulas give the simplest whole-number ratio (like CH₂O for glucose, C₆H₁₂O₆).
Chemical reactions come in five main types that you'll need to recognize: synthesis (combines elements), decomposition (breaks compounds down), single replacement (one element replaces another), double replacement (elements swap partners), and combustion (always produces CO₂, H₂O, and heat).
The mole concept connects the microscopic world of atoms with measurable quantities in the lab. To convert between grams and moles, use the formula: moles = mass ÷ molar mass. When balancing equations, remember that atoms must be conserved - what goes in must come out!
Remember: Phase changes involve energy changes! When a substance melts or boils, it absorbs energy (endothermic), and when it condenses or freezes, it releases energy (exothermic).
Gas laws help predict how gases behave under different conditions. The key relationships are Boyle's Law , Charles' Law , and the Ideal Gas Law . Vapor pressure increases with temperature and surface area but decreases with stronger intermolecular forces.
Acids, Bases & Nuclear Chemistry
Acids and bases are everywhere - from the vinegar in your kitchen to the soap in your bathroom! Acids have pH values below 7, taste sour, and produce hydrogen gas with certain metals. Bases have pH values above 7 and feel slippery. The pH scale runs from 0-14, with each number representing a tenfold change in hydrogen ion concentration.
Two important acid-base theories to know: Arrhenius theory says acids produce H⁺ ions in water while bases produce OH⁻ ions. Bronsted-Lowry theory describes acids as proton donors and bases as proton acceptors, forming conjugate pairs during reactions.
Electrochemistry explores how chemical reactions can produce electricity (voltaic cells) or how electricity can drive chemical reactions (electrolytic cells). In these cells, oxidation (loss of electrons) happens at the anode, while reduction (gain of electrons) occurs at the cathode.
Nuclear Fact: Unlike chemical reactions that involve electron rearrangements, nuclear reactions change the atom's nucleus itself through processes like radioactive decay, fission (splitting atoms), or fusion (combining atoms).
Organic chemistry deals with carbon-based compounds found in living things. Different functional groups give organic molecules their properties. Remember that saturated hydrocarbons (alkanes) have only single bonds, while unsaturated hydrocarbons have double or triple bonds, making them more reactive. Generally, the larger the organic molecule, the stronger its intermolecular forces and the higher its melting and boiling points.
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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
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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
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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 Chemistry Regents Review Guide
Chemistry is the science that explores matter, its properties, and how substances interact. This summary covers essential high school chemistry concepts from atomic structure to organic chemistry, breaking down complex ideas into manageable chunks you'll need for exams and labs.
Classification of Matter & Atomic Structure
Ever wonder what everything around you is actually made of? All matter falls into either pure substances (elements and compounds) or mixtures (homogeneous or heterogeneous). We separate mixtures using different methods based on their properties: distillation for different boiling points, chromatography for varying molecular polarity, and filtration for different particle sizes.
Atoms are the building blocks of everything! To understand them, remember that atomic mass - atomic number = number of neutrons. When electrons move between energy levels in atoms, they release energy as light, creating distinctive bright line spectra that act like atomic fingerprints.
The periodic table organizes elements logically, with metals on the left (good conductors, malleable, low electronegativity) and nonmetals on the right (poor conductors, brittle, high electronegativity). As you move across a period, electronegativity and ionization energy increase, while moving down a group decreases both.
Quick Tip: Remember that some elements exist in different forms called allotropes - like carbon appearing as both diamonds and graphite - same element, completely different properties!
Understanding bonds between atoms is crucial. Covalent bonds share electrons between nonmetals, creating compounds with low melting points that don't conduct electricity. Ionic bonds transfer electrons (like in Ca(NO₃)₂), forming strong compounds with high melting points that conduct electricity when dissolved or melted.
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Chemical Language & Reactions
Chemical formulas are like recipes that tell you exactly what's in a compound. Molecular formulas show the actual number of atoms (like H₂O), while empirical formulas give the simplest whole-number ratio (like CH₂O for glucose, C₆H₁₂O₆).
Chemical reactions come in five main types that you'll need to recognize: synthesis (combines elements), decomposition (breaks compounds down), single replacement (one element replaces another), double replacement (elements swap partners), and combustion (always produces CO₂, H₂O, and heat).
The mole concept connects the microscopic world of atoms with measurable quantities in the lab. To convert between grams and moles, use the formula: moles = mass ÷ molar mass. When balancing equations, remember that atoms must be conserved - what goes in must come out!
Remember: Phase changes involve energy changes! When a substance melts or boils, it absorbs energy (endothermic), and when it condenses or freezes, it releases energy (exothermic).
Gas laws help predict how gases behave under different conditions. The key relationships are Boyle's Law , Charles' Law , and the Ideal Gas Law . Vapor pressure increases with temperature and surface area but decreases with stronger intermolecular forces.
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Acids, Bases & Nuclear Chemistry
Acids and bases are everywhere - from the vinegar in your kitchen to the soap in your bathroom! Acids have pH values below 7, taste sour, and produce hydrogen gas with certain metals. Bases have pH values above 7 and feel slippery. The pH scale runs from 0-14, with each number representing a tenfold change in hydrogen ion concentration.
Two important acid-base theories to know: Arrhenius theory says acids produce H⁺ ions in water while bases produce OH⁻ ions. Bronsted-Lowry theory describes acids as proton donors and bases as proton acceptors, forming conjugate pairs during reactions.
Electrochemistry explores how chemical reactions can produce electricity (voltaic cells) or how electricity can drive chemical reactions (electrolytic cells). In these cells, oxidation (loss of electrons) happens at the anode, while reduction (gain of electrons) occurs at the cathode.
Nuclear Fact: Unlike chemical reactions that involve electron rearrangements, nuclear reactions change the atom's nucleus itself through processes like radioactive decay, fission (splitting atoms), or fusion (combining atoms).
Organic chemistry deals with carbon-based compounds found in living things. Different functional groups give organic molecules their properties. Remember that saturated hydrocarbons (alkanes) have only single bonds, while unsaturated hydrocarbons have double or triple bonds, making them more reactive. Generally, the larger the organic molecule, the stronger its intermolecular forces and the higher its melting and boiling points.
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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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Pure Substances & Mixtures
A pure substance is a form of matter that has a constant composition and properties that are constant throughout the sample.
ChemistryAtomic Structure & Bonding
Explore the fundamentals of atomic structure and bonding, including separation techniques, isotopes, relative atomic mass, and chemical nomenclature. This summary covers key concepts such as covalent and ionic bonding, electron configuration, and the periodic table, providing a comprehensive overview for students studying chemistry.
ChemistryS3
Most popular content: Acid-base Chemistry
Most popular content in AP Chemistry
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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
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