ScienceVerseLearning path: pH
The concepts to learn before pH, in order. Each step links to its page and, where one exists, its quiz.
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Your path
- Acids and BasesDirect prerequisite
Acids and bases are two complementary families of substances. In the Brønsted–Lowry picture (1923), an acid donates a proton (H⁺) and a base accepts one, so every acid–base reaction is a proton transfer. Strong acids such as hydrochloric acid ionise essentially completely in water, while weak acids such as acetic acid ionise only slightly. When an acid and a base react in the right proportions they neutralise each other, typically forming a salt and — for hydroxide bases — water.
- pHYour goal
pH is a number that expresses how acidic or basic a water-based solution is. It is the negative base-10 logarithm of the hydronium ion concentration, so each step of one pH unit is a tenfold change. At 25 °C a neutral solution has pH 7, acidic solutions are below 7 and basic solutions above 7; the neutral point itself shifts with temperature.