The pH Scale
The pH scale runs from 0 to 14 and measures how acidic or alkaline a solution is, based on its hydrogen ion concentration.
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The pH scale runs from 0 to 14 and measures how acidic or alkaline a solution is, based on its hydrogen ion concentration.
- Each pH step is a tenfold change
- Universal indicator shows colour
- Neutral is pH 7
🧠 Quick quiz
Three questions. Score 2 or more to complete the topic.
What is The pH Scale?
Within Chemistry, which covers atoms, bonding, reactions, the periodic table, organic chemistry and the chemistry of everyday life, this topic explains The pH Scale. 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 The pH Scale in your own words and give one example from everyday life. If you can do that, you have understood the core idea.
Understanding The pH Scale helps you explain why substances behave as they do, from cleaning products and food to medicines.
The pH Scale in detail
The pH scale runs from 0 to 14 and measures how acidic or alkaline a solution is. Below 7 is acidic, 7 is neutral (pure water) and above 7 is alkaline. Universal indicator gives a colour range from red (strong acid) through green (neutral) to purple (strong alkali), and a pH meter gives a precise value.
The scale is logarithmic: each unit change is a tenfold change in hydrogen ion concentration, so pH 3 is ten times more acidic than pH 4. The pH of soils, blood, swimming pools and food matters, and many biological and industrial processes need it carefully controlled.
How the interactive helps you understand The pH Scale
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 The pH Scale.
Real-life uses and examples
- Link The pH Scale to everyday products such as cleaning agents, food and medicines.
- Read a chemical equation or diagram and work out what The pH Scale shows.
- Explain The pH Scale in an exam by linking the particles involved to what you observe.
Common mistakes to avoid
- Mixing up the names of substances or ions when you describe The pH Scale.
- Describing what happens without explaining the particles or bonds involved.
- Learning the definition without testing it. Use the quiz and the interactive to check that you can apply the idea.
Frequently asked questions about The pH Scale
What is The pH Scale?
The pH scale runs from 0 to 14 and measures how acidic or alkaline a solution is, based on its hydrogen ion concentration.
What are the most important points about The pH Scale?
The main points are: Each pH step is a tenfold change; Universal indicator shows colour; Neutral is pH 7.
Why is The pH Scale useful?
Understanding The pH Scale helps you explain why substances behave as they do, from cleaning products and food to medicines.
How can I practise The pH Scale?
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 The pH Scale?
Related topics in Chemistry include Making Soluble Salts, Reactivity Series, Oxidation and Reduction.