Acids and Alkalis
Acids release hydrogen ions in water and alkalis release hydroxide ions, and their strength is measured on the pH scale.
▶ Interact
Play with the controls to see the idea in action.
📘 Learn
Acids release hydrogen ions in water and alkalis release hydroxide ions, and their strength is measured on the pH scale.
- pH below 7 is acidic
- pH above 7 is alkaline
- Indicators change colour with pH
🧠 Quick quiz
Three questions. Score 2 or more to complete the topic.
What is Acids and Alkalis?
Within Chemistry, which covers atoms, bonding, reactions, the periodic table, organic chemistry and the chemistry of everyday life, this topic explains Acids and Alkalis. Chemistry links what you can see in the lab to the particles and bonds behind it, so each topic here shows that link in a model.
Check that you can explain Acids and Alkalis in your own words and give one example from everyday life. If you can do that, you have understood the core idea.
Understanding Acids and Alkalis helps you explain why substances behave as they do, from cleaning products and food to medicines.
Acids and Alkalis in detail
Acids are substances that release hydrogen ions (H⁺) in water, such as hydrochloric, sulfuric and nitric acid. Alkalis are soluble bases that release hydroxide ions (OH⁻) in water, such as sodium hydroxide. Indicators such as litmus and universal indicator change colour to show acidity.
Acids react with metals to give a salt and hydrogen, with carbonates to give a salt, water and carbon dioxide, and with bases to give a salt and water. Acids taste sour and alkalis feel soapy, but you should never taste or touch chemicals in the lab. They are used in food, cleaning and manufacturing.
How the interactive helps you understand Acids and Alkalis
Watch the pH scale in the interactive. Use any sliders or buttons it offers to change the values and see how the pH scale responds.
Before you change anything, predict the result. Then change one value at a time and check whether your prediction was right. This is a quick way to build a correct mental model of Acids and Alkalis.
Real-life uses and examples
- Use Acids and Alkalis to explain what happens in a lab experiment and why.
- Link Acids and Alkalis to everyday products such as cleaning agents, food and medicines.
- Read a chemical equation or diagram and work out what Acids and Alkalis shows.
Common mistakes to avoid
- Describing what happens without explaining the particles or bonds involved.
- Mixing up the names of substances or ions when you describe Acids and Alkalis.
- Learning the definition without testing it. Use the quiz and the interactive to check that you can apply the idea.
Frequently asked questions about Acids and Alkalis
What is Acids and Alkalis?
Acids release hydrogen ions in water and alkalis release hydroxide ions, and their strength is measured on the pH scale.
What are the most important points about Acids and Alkalis?
The main points are: pH below 7 is acidic; pH above 7 is alkaline; Indicators change colour with pH.
Why is Acids and Alkalis useful?
Understanding Acids and Alkalis helps you explain why substances behave as they do, from cleaning products and food to medicines.
How can I practise Acids and Alkalis?
Open the interactive at the top of this page and change the controls one at a time. Predict the result before each change, then take the three-question quiz. A score of two or more marks the topic as complete on this device.
Which topics are related to Acids and Alkalis?
Related topics in Chemistry include Neutralisation, Titration, Extraction of Metals.