Scientists Say: Acid

This type of chemical contains hydrogen ions in a solution — and leaves a sour taste


Lemon juice tastes sour to us because it is acidic.

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Acid    (noun, “AAH-sid”)

This is any chemical that, when placed in a solution, releases hydrogen ions — atoms with a tiny positive electric charge. The charges make these ions react with bases, which are ions of another type. (Known as hydroxyl  ions, those other ions have a negative electric charge.)  Acids can eat away at many substances and tend to taste sour. When measured on a pH scale — a zero to 14 ranking of how acidic or basic chemicals are — acids measure below 7.0.  And the lower the pH, the stronger — more powerful — the acid.

In a sentence

Acid can help leach dangerous lead out of soils

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Power Words

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acid    A chemical that releases hydrogen ions when dissolved in a solution. Acids have a sour taste and have a pH ranking of less than 7.0.

acidic  An adjective for materials that contain acid. These materials often are capable of eating away at some minerals such as carbonate, or preventing their formation in the first place.

base  (in chemistry) A chemical that produces hydroxide ions (OH-) in a solution. Basic solutions are also referred to as alkaline. (in genetics) A shortened version of the term nucleobase. These bases are building blocks of DNA and RNA molecules.

hydrogen  The lightest element in the universe. As a gas, it is colorless, odorless and highly flammable. It’s an integral part of many fuels, fats and chemicals that make up living tissues.

hydroxyl    A chemical group, or pairing. It’s made from an oxygen atom bound to a hydrogen atom, OH. In bases, it is negatively charged.

ion   An atom or molecule with an electric charge due to the loss or gain of one or more electrons.

pH    A measure of a solution’s acidity. A pH of 7 is perfectly neutral. Acids have a pH lower than 7; the farther from 7, the stronger the acid. Alkaline solutions, called bases, have a pH higher than 7; again, the farther above 7, the stronger the base.

Bethany Brookshire was a longtime staff writer at Science News Explores and is the author of the book Pests: How Humans Create Animal Villains. She has a Ph.D. in physiology and pharmacology and likes to write about neuroscience, biology, climate and more. She thinks Porgs are an invasive species.

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