pH scale
A scale from 0 to 14 showing how acidic or alkaline a solution is. Below 7 is acid, 7 is neutral and above 7 is alkaline.
Last updated
Analogy
Like a temperature scale for acidity, with 7 in the middle as normal.
Example
Stomach acid: 1Lemon juice: 2Pure water: 7Bleach: 12
In practice
Pure water is pH 7. Lemon juice is about 2. Soap is about 10.
Practice
Flashcards
- What is the pH of a neutral solution?7.
Questions people ask
What does each step on the pH scale mean?
Each step is a tenfold change in acidity. A solution with pH 3 is ten times more acidic than one with pH 4, and one hundred times more than pH 5. That is why a small change in the number is a big change in the chemistry.
How do you measure pH accurately?
A pH meter with a probe gives a precise number, while universal indicator paper or solution gives a rough value by colour. Indicator colours can be hard to judge in coloured solutions, so a meter is better for exact work and for experiments with several steps.