Biology
Chemistry
AP Chemistry
English
AP English Literature
Chemistry
Dec 18, 2025
227
4 pages
Knowunity Official @team.knowunity
Chemistry is the study of matter, its properties, and the changes it undergoes. This chapter introduces the fundamental... Show more
When you look around, everything you see is made of incredibly tiny particles. Atoms are the smallest units of an element that still maintain that element's properties, while molecules form when two or more atoms join together to act as a single unit. This arrangement of atoms is what gives substances their unique properties.
Chemical reactions happen when substances transform into different substances through the reorganization of atoms. This process is fundamental to everything from cooking food to your body processing nutrients!
Science isn't just a collection of facts—it's a dynamic process for discovering how the world works. The scientific method provides the framework scientists use to ask questions, make observations, and develop explanations. This methodical approach involves observation, creating hypotheses, conducting experiments, and developing theories that can make predictions.
💡 Real-world connection Every time you see a chemical change—like food cooking, metal rusting, or plants growing—you're witnessing atoms rearranging themselves through chemical reactions!
Scientists organize their understanding of the world using several key concepts. A law summarizes observable, repeatable behaviors, while a hypothesis offers a possible explanation for an observation. When multiple tested hypotheses work together to explain a natural phenomenon, they form a theory or model.
Measurements are essential to science because they allow us to quantify our observations. Every measurement consists of two parts a number and a unit. The International System of Units (SI) provides standard units that scientists worldwide use, including meters for length, kilograms for mass, and seconds for time.
When scientists communicate their findings, they need a common language. The SI system creates this shared foundation with seven fundamental units that can be combined to measure virtually anything in the universe.
⚠️ Watch out! Don't confuse the terms "theory" and "hypothesis" in science. A scientific theory isn't just a guess—it's a comprehensive explanation supported by substantial evidence and testing.
Did you know that mass and weight are not the same thing? Mass measures an object's resistance to changes in motion and remains constant regardless of location. Weight, however, is the force of gravity acting on an object and varies depending on gravitational field strength.
Every measurement contains some degree of uncertainty. When recording measurements, scientists include all certain digits plus the first uncertain digit. This practice reflects the reality that no measurement is absolutely perfect.
Scientists distinguish between accuracy (how close a measurement is to the true value) and precision (how close repeated measurements are to each other). You can think of accuracy as hitting the bullseye, while precision is hitting the same spot consistently—even if it's not the bullseye.
Significant figures help communicate measurement precision. Remember these key rules non-zero digits are always significant; zeros between non-zero digits (captive zeros) count as significant; and zeros before non-zero digits (leading zeros) don't count. Trailing zeros after the decimal point are significant.
🔍 Study tip When doing chemistry calculations, your final answer can't be more precise than your least precise measurement. Always check your significant figures!
Matter is anything that occupies space and has mass—essentially everything you can physically touch or observe. This foundational concept helps us classify and understand the physical world around us.
The three primary states of matter exhibit distinctly different properties. Solids maintain a fixed shape and volume, resistant to deformation. Liquids flow freely, taking the shape of their container while maintaining a consistent volume. Gases expand to fill any container completely, with both volume and shape dependent on their surroundings.
These states of matter differ because of how the particles are arranged and how strongly they interact with one another. Temperature and pressure can cause matter to change from one state to another, like when water freezes into ice or boils into steam.
🌡️ Think about it Every time you see water as ice, liquid, or steam, you're observing the same molecules in different states of matter. Only the energy and arrangement of molecules changes!
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.
You can download the app in the Google Play Store and in the Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
4
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Learn about the formation of cations and anions, their charges, and the properties of ionic compounds, and lewis structures
ChemistryThis is about atoms and molecules.
ChemistryExplore essential laboratory techniques including chromatography, simple and fractional distillation, and filtration. Understand the principles of separation methods, the properties of metals and non-metals, and the development of the periodic table. This summary covers key concepts such as atomic structure, mixtures, and balancing chemical equations, making it a valuable resource for chemistry students.
Chemistry35 elements of the periodic table of elements. Consists of all events from the first two periods and some transition metals
ChemistryLearn about physical and chemical changes, properties, and examples in this informative article.
ChemistryChemistry chemical changes flashcards
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
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
Knowunity Official
@team.knowunity
Chemistry is the study of matter, its properties, and the changes it undergoes. This chapter introduces the fundamental building blocks of the chemical world and the scientific approach used to understand them—laying groundwork for how scientists observe, measure, and describe... Show more
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
When you look around, everything you see is made of incredibly tiny particles. Atoms are the smallest units of an element that still maintain that element's properties, while molecules form when two or more atoms join together to act as a single unit. This arrangement of atoms is what gives substances their unique properties.
Chemical reactions happen when substances transform into different substances through the reorganization of atoms. This process is fundamental to everything from cooking food to your body processing nutrients!
Science isn't just a collection of facts—it's a dynamic process for discovering how the world works. The scientific method provides the framework scientists use to ask questions, make observations, and develop explanations. This methodical approach involves observation, creating hypotheses, conducting experiments, and developing theories that can make predictions.
💡 Real-world connection: Every time you see a chemical change—like food cooking, metal rusting, or plants growing—you're witnessing atoms rearranging themselves through chemical reactions!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Scientists organize their understanding of the world using several key concepts. A law summarizes observable, repeatable behaviors, while a hypothesis offers a possible explanation for an observation. When multiple tested hypotheses work together to explain a natural phenomenon, they form a theory or model.
Measurements are essential to science because they allow us to quantify our observations. Every measurement consists of two parts: a number and a unit. The International System of Units (SI) provides standard units that scientists worldwide use, including meters for length, kilograms for mass, and seconds for time.
When scientists communicate their findings, they need a common language. The SI system creates this shared foundation with seven fundamental units that can be combined to measure virtually anything in the universe.
⚠️ Watch out! Don't confuse the terms "theory" and "hypothesis" in science. A scientific theory isn't just a guess—it's a comprehensive explanation supported by substantial evidence and testing.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Did you know that mass and weight are not the same thing? Mass measures an object's resistance to changes in motion and remains constant regardless of location. Weight, however, is the force of gravity acting on an object and varies depending on gravitational field strength.
Every measurement contains some degree of uncertainty. When recording measurements, scientists include all certain digits plus the first uncertain digit. This practice reflects the reality that no measurement is absolutely perfect.
Scientists distinguish between accuracy (how close a measurement is to the true value) and precision (how close repeated measurements are to each other). You can think of accuracy as hitting the bullseye, while precision is hitting the same spot consistently—even if it's not the bullseye.
Significant figures help communicate measurement precision. Remember these key rules: non-zero digits are always significant; zeros between non-zero digits (captive zeros) count as significant; and zeros before non-zero digits (leading zeros) don't count. Trailing zeros after the decimal point are significant.
🔍 Study tip: When doing chemistry calculations, your final answer can't be more precise than your least precise measurement. Always check your significant figures!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Matter is anything that occupies space and has mass—essentially everything you can physically touch or observe. This foundational concept helps us classify and understand the physical world around us.
The three primary states of matter exhibit distinctly different properties. Solids maintain a fixed shape and volume, resistant to deformation. Liquids flow freely, taking the shape of their container while maintaining a consistent volume. Gases expand to fill any container completely, with both volume and shape dependent on their surroundings.
These states of matter differ because of how the particles are arranged and how strongly they interact with one another. Temperature and pressure can cause matter to change from one state to another, like when water freezes into ice or boils into steam.
🌡️ Think about it: Every time you see water as ice, liquid, or steam, you're observing the same molecules in different states of matter. Only the energy and arrangement of molecules changes!
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.
You can download the app in the Google Play Store and in the Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
4
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Learn about the formation of cations and anions, their charges, and the properties of ionic compounds, and lewis structures
ChemistryThis is about atoms and molecules.
ChemistryExplore essential laboratory techniques including chromatography, simple and fractional distillation, and filtration. Understand the principles of separation methods, the properties of metals and non-metals, and the development of the periodic table. This summary covers key concepts such as atomic structure, mixtures, and balancing chemical equations, making it a valuable resource for chemistry students.
Chemistry35 elements of the periodic table of elements. Consists of all events from the first two periods and some transition metals
ChemistryLearn about physical and chemical changes, properties, and examples in this informative article.
ChemistryChemistry chemical changes flashcards
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
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
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