Ph scale

Science

Definition

The pH scale measures how acidic or basic a solution is, ranging from 0 to 14. A pH of 7 is neutral, below 7 is acidic, and above 7 is basic (alkaline). Each whole number change represents a tenfold change in hydrogen ion concentration.

Examples

  • Lemon juice with a pH around 2 (strongly acidic)
  • Pure water at pH 7 (neutral)
  • Bleach with a pH around 13 (strongly basic)
Key Fact

pH = −log[H⁺]; each pH unit = 10× change in [H⁺].

Related Terms

Acid-base theory Ph calculations Buffers Strong vs weak acids

Study This Concept

Practice pH scale with free review games in these units:

Chemistry Unit 8: Acids Bases and pH