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International System of Measurement
The International System (SI) forms the backbone of scientific measurements worldwide. It's built on seven basic quantities that help scientists communicate precisely: length (meters), mass (kilograms), time (seconds), electric current (amperes), temperature (Kelvin), amount of substance (moles), and luminous intensity (candelas).
When taking measurements, two factors affect accuracy: how well you use the measuring instruments and the precision of the instruments themselves. To solve measurement problems, scientists use the unit factor method—a technique that helps cancel unwanted units through fixed relationships between quantities.
Metric prefixes make conversions super easy because they're all based on powers of 10. For example, a kilometer (1000 meters) uses the prefix "kilo" (k) which represents 10³ or 1000. Common prefixes range from "giga" (10⁹) all the way down to "pico" (10⁻¹²).
Pro Tip: You don't need to memorize all the metric prefixes—focus on the most commonly used ones like kilo (1000×), centi (0.01×), and milli (0.001×). These will handle most conversions you'll encounter in class.
Temperature Scales
Temperature can be measured using three different scales that you'll encounter in science classes. The Fahrenheit scale (used mainly in the US) sets water's freezing point at 32°F and boiling at 212°F, with 180 divisions between them.
The Celsius scale (or centigrade) is more straightforward—water freezes at 0°C and boils at 100°C. This scale is used almost everywhere in the world and in all scientific work. To convert between these scales, use these formulas: F = (9/5)C + 32 or C = 5/9.
The Kelvin scale is the scientific standard used in the International System. It's an absolute temperature scale, meaning 0 K is the lowest possible temperature (absolute zero). Converting from Celsius is simple: just add 273 . Unlike the other scales, Kelvin doesn't use the degree symbol—it's just K.
Remember: For science class, you'll most often need to convert between Celsius and Kelvin. The size of one unit is the same in both scales—the difference is just where they start counting from!
Volume Measurement
Volume tells us how much space an object occupies, and we measure it differently depending on what we're measuring. For regular solids with straight edges, calculating volume is simple—just multiply length × width × height . The result is expressed in cubic units like cubic centimeters (cm³).
Liquids are typically measured in liters (L) or milliliters (mL), though cubic measurements work too. When reading liquid volumes in graduated cylinders, remember to read at eye level and check the meniscus—for clear liquids, read the bottom curve; for colored liquids, read the top.
Measuring irregular solids (objects with uneven shapes) requires a different approach called the displacement method. Simply place the object in water and measure how much the water level rises—the volume of water displaced equals the volume of the object.
Real-Life Application: The displacement method is how Archimedes famously discovered how to test if a crown was made of pure gold without damaging it. This same technique helps you find the volume of oddly shaped objects for science projects!
Density
Density reveals how much mass is packed into a given volume, making it a key property that helps us identify substances. Each material has its own characteristic density, which doesn't change regardless of sample size.
Calculating density is straightforward: divide mass by volume . The standard units for density are grams per cubic centimeter or grams per milliliter . Water has a density of 1 g/cm³, which serves as a convenient reference point.
This property explains why some objects float and others sink. The simple rule is: if an object's density is less than water's density , it will float; if its density is greater, it will sink. This explains why massive ships made of steel (which is denser than water) can float—their hollow design gives them an overall density less than water.
Cool Fact: Density differences explain why oil floats on water, why helium balloons rise in air, and why it's easier to float in the extremely salty Dead Sea than in a swimming pool!
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?
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Is Knowunity really free of charge?
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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
Understanding SI Units and Measurements
Measurement is a fundamental skill in science that helps us quantify the world around us. The International System (SI) provides standardized units that scientists worldwide agree upon, giving us a common language to describe physical quantities. Understanding measurement systems helps... Show more
International System of Measurement
The International System (SI) forms the backbone of scientific measurements worldwide. It's built on seven basic quantities that help scientists communicate precisely: length (meters), mass (kilograms), time (seconds), electric current (amperes), temperature (Kelvin), amount of substance (moles), and luminous intensity (candelas).
When taking measurements, two factors affect accuracy: how well you use the measuring instruments and the precision of the instruments themselves. To solve measurement problems, scientists use the unit factor method—a technique that helps cancel unwanted units through fixed relationships between quantities.
Metric prefixes make conversions super easy because they're all based on powers of 10. For example, a kilometer (1000 meters) uses the prefix "kilo" (k) which represents 10³ or 1000. Common prefixes range from "giga" (10⁹) all the way down to "pico" (10⁻¹²).
Pro Tip: You don't need to memorize all the metric prefixes—focus on the most commonly used ones like kilo (1000×), centi (0.01×), and milli (0.001×). These will handle most conversions you'll encounter in class.
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Temperature Scales
Temperature can be measured using three different scales that you'll encounter in science classes. The Fahrenheit scale (used mainly in the US) sets water's freezing point at 32°F and boiling at 212°F, with 180 divisions between them.
The Celsius scale (or centigrade) is more straightforward—water freezes at 0°C and boils at 100°C. This scale is used almost everywhere in the world and in all scientific work. To convert between these scales, use these formulas: F = (9/5)C + 32 or C = 5/9.
The Kelvin scale is the scientific standard used in the International System. It's an absolute temperature scale, meaning 0 K is the lowest possible temperature (absolute zero). Converting from Celsius is simple: just add 273 . Unlike the other scales, Kelvin doesn't use the degree symbol—it's just K.
Remember: For science class, you'll most often need to convert between Celsius and Kelvin. The size of one unit is the same in both scales—the difference is just where they start counting from!
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Volume Measurement
Volume tells us how much space an object occupies, and we measure it differently depending on what we're measuring. For regular solids with straight edges, calculating volume is simple—just multiply length × width × height . The result is expressed in cubic units like cubic centimeters (cm³).
Liquids are typically measured in liters (L) or milliliters (mL), though cubic measurements work too. When reading liquid volumes in graduated cylinders, remember to read at eye level and check the meniscus—for clear liquids, read the bottom curve; for colored liquids, read the top.
Measuring irregular solids (objects with uneven shapes) requires a different approach called the displacement method. Simply place the object in water and measure how much the water level rises—the volume of water displaced equals the volume of the object.
Real-Life Application: The displacement method is how Archimedes famously discovered how to test if a crown was made of pure gold without damaging it. This same technique helps you find the volume of oddly shaped objects for science projects!
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Improve your grades
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By signing up you accept Terms of Service and Privacy Policy
Density
Density reveals how much mass is packed into a given volume, making it a key property that helps us identify substances. Each material has its own characteristic density, which doesn't change regardless of sample size.
Calculating density is straightforward: divide mass by volume . The standard units for density are grams per cubic centimeter or grams per milliliter . Water has a density of 1 g/cm³, which serves as a convenient reference point.
This property explains why some objects float and others sink. The simple rule is: if an object's density is less than water's density , it will float; if its density is greater, it will sink. This explains why massive ships made of steel (which is denser than water) can float—their hollow design gives them an overall density less than water.
Cool Fact: Density differences explain why oil floats on water, why helium balloons rise in air, and why it's easier to float in the extremely salty Dead Sea than in a swimming pool!
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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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