Skip to content
Know.itKnow.it
Create an animated lesson
On request

This article is free to read. Creating a lesson uses your daily or stored credits; review the language and settings before starting.

What is the pH scale?

ScienceLesson on requestFree to read

Quick answer

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.

Key things to understand

  1. It runs from 0 (acidic) to 14 (basic), with 7 neutral.
  2. It measures the concentration of hydrogen ions.
  3. Each whole step is a tenfold change in acidity.
  4. Lemon juice is acidic (~2); soap is basic (~9–10).

People also ask

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.