How Does the Acidity Scale Work?
When acid is added to water, hydrogen ions form in the solution. Scientists measure the acidity of a solution using an acidity, or pH, scale. The pH scale tells you the concentration of hydronium ions in a solution.
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History
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In 1909, Dr. Soren Sorenson, a Danish biochemist, developed the pH scale. The pH scale ranges in value from a minimum value of 0 to a maximum of 14. Each whole unit decrease denotes a tenfold increase in acidity, meaning a solution with a pH of 1 is 10 times more acidic than one with a pH of 2.
Description
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pH values less than 7 designate acidic chemicals. pH values higher than 7 correlate with chemicals that are bases, or alkaline. A pH value of 7, according to the U.S. Environmental Protection Agency, denotes a neutral substance such as distilled water that is neither an acid nor a base.
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Measuring Acidity
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Acidity of a substance is measured using specialized instruments or paper. Blue and red litmus paper is used to test solutions for the presence of acids or bases, respectively. Alkacid paper indicates if a substance is an acid or base while giving a rough estimate of the pH value. A pH meter offers more accurate measurements of pH.
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References
- California State University at Northridge: The Self-Ionization of Water and pH
- Chemistry Hypermedia Project at Virginia Tech: Notes on Acids and Bases
- New World Encyclopedia: pH
- NT Curriculum Project at the University of Wisconsin: pH Paper Module
- United States Environmental Protection Agency: What Is pH?
