Science
What is The pH scale?
The pH scale measures how acidic or basic a substance is, running from 0 (very acidic) to 14 (very basic), with 7 being neutral. It's based on the concentration of hydrogen ions, and each step is a tenfold change in acidity.
See it, don’t just read it.
Watch a 2-minute lesson with voice + animation that explains the ph scale.
Key things to understand
- 1It runs from 0 (acidic) to 14 (basic), with 7 neutral.
- 2It measures the concentration of hydrogen ions.
- 3Each whole step is a tenfold change in acidity.
- 4Lemon juice is acidic (~2); soap is basic (~9–10).
Frequently asked questions
- What does the pH scale measure?
- How acidic or basic a substance is, based on its concentration of hydrogen ions.
- What is a neutral pH?
- A pH of 7, like pure water — neither acidic nor basic.
- Why does each pH step matter so much?
- Because the scale is logarithmic: each step is a tenfold change, so pH 4 is ten times more acidic than pH 5.