The pH scalemeasures acidity and alkalinity, ranging from 0-14.... Show more
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14/09/2025
Chemistry
Chemical changes
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14 Sept 2025
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Understanding the pH Scale: Fun Examples and Experiments for Kids
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Making Salts and the Reactivity Series
Salts can be produced through various chemical reactions involving acids. For example, copper chloride is made by reacting hydrochloric acid with copper oxide:
CuO + 2HCl → CuCl₂ + H₂O
The process involves:
- Warming the dilute acid
- Adding the insoluble base until excess remains
- Filtering out excess solid
- Evaporating the solution to form crystals
Highlight: The reactivity series lists metals in order of their reactivity towards other substances, based on how easily they lose electrons to form positive ions.
Metals react with acids to form salts and hydrogen gas:
Acid + Metal → Salt + Hydrogen
Example: Magnesium reacts with hydrochloric acid to form magnesium chloride and hydrogen gas: Mg + 2HCl → MgCl₂ + H₂
The speed of the reaction indicates the metal's reactivity:
- More reactive metals like potassium and sodium react explosively
- Less reactive metals like magnesium and zinc react less violently
- Copper generally doesn't react with cold, dilute acids
Vocabulary: Redox reactions involve the transfer of electrons, where oxidation is the loss of electrons and reduction is the gain of electrons.
Redox Reactions and Further Concepts
Redox reactions play a crucial role in understanding chemical changes involving acids, bases, and metals. These reactions involve the transfer of electrons between species:
- Oxidation: Loss of electrons
- Reduction: Gain of electrons
Definition: A redox reaction occurs when one species is oxidized and another is reduced simultaneously.
The reactivity series of metals provides insight into how readily different metals undergo redox reactions:
- Potassium
- Sodium
- Calcium
- Magnesium ...
Highlight: The more reactive a metal is, the more easily it loses electrons and reacts with other substances like water or acids.
Investigating metal reactivity can be done by measuring temperature changes during reactions. In a fair experiment, more reactive metals should produce greater temperature increases.
Example: Comparing the temperature change when magnesium and zinc react with hydrochloric acid can indicate their relative reactivity.
Metals also react with water, with more reactive metals producing more vigorous reactions. This behavior correlates with their position in the reactivity series.
Vocabulary: Effervescence is the production of bubbles during a chemical reaction, often seen when metals react with acids to produce hydrogen gas.
Understanding these concepts is crucial for predicting and explaining chemical reactions involving acids, bases, and metals in various contexts, from laboratory experiments to real-world applications.
Chemical Changes: Acids and Bases
The pH scale is a fundamental concept in chemistry, measuring the acidity or alkalinity of solutions. It ranges from 0 to 14, with lower values indicating higher acidity and higher values indicating greater alkalinity.
Definition: The pH scale measures the concentration of hydrogen ions in a solution, determining its acidity or alkalinity.
Acids and bases are defined by their behavior on the pH scale:
- Acids have a pH less than 7 and form H+ ions in water.
- Bases have a pH greater than 7 and can neutralize acids.
- Alkalis are bases that dissolve in water, forming OH- ions.
Highlight: Neutralization occurs when acids and bases react, forming salt and water.
The strength of acids is determined by their ionization in water:
- Strong acids completely ionize in water.
- Weak acids only partially ionize in water.
Example: Hydrochloric acid (HCl) is a strong acid, while acetic acid (CH₃COOH) is a weak acid.
Titration is a crucial process in acid-base chemistry:
- It determines the exact amount of acid needed to neutralize an alkali (or vice versa).
- This data is used to calculate acid or alkali concentration.
Vocabulary: Phenolphthalein is an indicator used in titrations, turning pink in alkaline conditions and colorless in neutral or acidic conditions.
Acids react with various substances:
- Metal oxides and hydroxides (alkalis) react with acids to form salt and water.
- Metal carbonates react with acids to produce salt, water, and carbon dioxide.
Example: 2HCl + CuO → CuCl₂ + H₂O
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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
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
Understanding the pH Scale: Fun Examples and Experiments for Kids
The pH scalemeasures acidity and alkalinity, ranging from 0-14. Acids have a pH below 7, while bases have a pH above 7. Neutralization occurs when acids and bases react. Strong acids fully ionize in water, while weak acids only... Show more
Making Salts and the Reactivity Series
Salts can be produced through various chemical reactions involving acids. For example, copper chloride is made by reacting hydrochloric acid with copper oxide:
CuO + 2HCl → CuCl₂ + H₂O
The process involves:
- Warming the dilute acid
- Adding the insoluble base until excess remains
- Filtering out excess solid
- Evaporating the solution to form crystals
Highlight: The reactivity series lists metals in order of their reactivity towards other substances, based on how easily they lose electrons to form positive ions.
Metals react with acids to form salts and hydrogen gas:
Acid + Metal → Salt + Hydrogen
Example: Magnesium reacts with hydrochloric acid to form magnesium chloride and hydrogen gas: Mg + 2HCl → MgCl₂ + H₂
The speed of the reaction indicates the metal's reactivity:
- More reactive metals like potassium and sodium react explosively
- Less reactive metals like magnesium and zinc react less violently
- Copper generally doesn't react with cold, dilute acids
Vocabulary: Redox reactions involve the transfer of electrons, where oxidation is the loss of electrons and reduction is the gain of electrons.
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Redox Reactions and Further Concepts
Redox reactions play a crucial role in understanding chemical changes involving acids, bases, and metals. These reactions involve the transfer of electrons between species:
- Oxidation: Loss of electrons
- Reduction: Gain of electrons
Definition: A redox reaction occurs when one species is oxidized and another is reduced simultaneously.
The reactivity series of metals provides insight into how readily different metals undergo redox reactions:
- Potassium
- Sodium
- Calcium
- Magnesium ...
Highlight: The more reactive a metal is, the more easily it loses electrons and reacts with other substances like water or acids.
Investigating metal reactivity can be done by measuring temperature changes during reactions. In a fair experiment, more reactive metals should produce greater temperature increases.
Example: Comparing the temperature change when magnesium and zinc react with hydrochloric acid can indicate their relative reactivity.
Metals also react with water, with more reactive metals producing more vigorous reactions. This behavior correlates with their position in the reactivity series.
Vocabulary: Effervescence is the production of bubbles during a chemical reaction, often seen when metals react with acids to produce hydrogen gas.
Understanding these concepts is crucial for predicting and explaining chemical reactions involving acids, bases, and metals in various contexts, from laboratory experiments to real-world applications.
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Chemical Changes: Acids and Bases
The pH scale is a fundamental concept in chemistry, measuring the acidity or alkalinity of solutions. It ranges from 0 to 14, with lower values indicating higher acidity and higher values indicating greater alkalinity.
Definition: The pH scale measures the concentration of hydrogen ions in a solution, determining its acidity or alkalinity.
Acids and bases are defined by their behavior on the pH scale:
- Acids have a pH less than 7 and form H+ ions in water.
- Bases have a pH greater than 7 and can neutralize acids.
- Alkalis are bases that dissolve in water, forming OH- ions.
Highlight: Neutralization occurs when acids and bases react, forming salt and water.
The strength of acids is determined by their ionization in water:
- Strong acids completely ionize in water.
- Weak acids only partially ionize in water.
Example: Hydrochloric acid (HCl) is a strong acid, while acetic acid (CH₃COOH) is a weak acid.
Titration is a crucial process in acid-base chemistry:
- It determines the exact amount of acid needed to neutralize an alkali (or vice versa).
- This data is used to calculate acid or alkali concentration.
Vocabulary: Phenolphthalein is an indicator used in titrations, turning pink in alkaline conditions and colorless in neutral or acidic conditions.
Acids react with various substances:
- Metal oxides and hydroxides (alkalis) react with acids to form salt and water.
- Metal carbonates react with acids to produce salt, water, and carbon dioxide.
Example: 2HCl + CuO → CuCl₂ + H₂O
We thought you’d never ask...
What is the Knowunity AI companion?
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
Where can I download the Knowunity app?
You can download the app from Google Play Store and Apple App Store.
Is Knowunity really free of charge?
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.9/5
App Store
4.8/5
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user