Okuzeka
Chemistry vocabulary · Acids, Bases and Salts

pH

Meaning in chemistry, with examples

/ˌpiːˈeɪtʃ/nounCore term

In chemistry, pH means: A scale, usually from 0 to 14, that shows how acidic or basic a solution is. Below 7 is acidic, 7 is neutral at 25 °C and above 7 is basic; it equals −log[H⁺].

In Turkish: pH, pH değeri

How it is used

Used in every lab: you measure, check, adjust, raise or lower the pH with a pH meter or pH paper. Write it with a small p and a capital H, and say the letters: 'pee-aitch'.

Example sentences

  1. Adjust the pH of the buffer to 7.4 with dilute sodium hydroxide.

  2. The pH dropped from 6 to 3, so the solution is now a thousand times more acidic.

Common collocations

  • pH meter
  • pH paper
  • adjust the pH
  • low pH
  • pH value
  • acidA substance that releases hydrogen ions (H⁺) in water or, more generally, donates protons. Its water solutions have a pH below 7 and turn blue litmus paper red.
  • baseA substance that accepts protons (H⁺) or releases hydroxide ions (OH⁻) in water. Its solutions have a pH above 7 and turn red litmus paper blue.
  • bufferA solution that resists changes in pH when small amounts of acid or base are added. It usually contains a weak acid and its conjugate base, such as acetic acid and sodium acetate.
  • indicatorA substance that changes color at a certain pH or at the end of a reaction, used to show when a titration is complete. Phenolphthalein and methyl orange are common examples.
  • titrationA method for finding the unknown concentration of a solution by adding a solution of known concentration from a burette until the reaction between them is just complete.

This word in other fields

The same English word can have a different meaning in another field:

More terms: Acids, Bases and Salts

Practise with graded reading

Reading at the right level is the fastest way to make new words stick. Pick free English books by level: