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What is pH?

Acidic and alkaine (or "basic") are two extremes that describe substances, usually liquids or chemicals, just like hot and cold are two extremes that describe temperature. A substance that is neither acidic nor alkaline is neutral.

The pH scale measures how acidic or alkaline a substance is. The scale ranges from 0 to 14. A pH of 7 is neutral. A pH less than 7 is acidic, and a pH greater than 7 is basic. Pure water is neutral, with a pH of 7.0. When chemicals are mixed with water, the mixture can become some level of either acidic or alkaline. Vinegar and lemon juice are acidic substances, while laundry detergents and ammonia are alkaline.

graphic showing the range of pH levbels, from 0 (most acid) on the far left to 14 (most basic) on the far right. Graphic also shows the pH level of a variety of common substances such as battery acid, water, or shampoo. — What do the numbers mean? Each whole pH value is ten times stronger than the next outer or more extreme value. For example, a pH of 4 is ten times more acidic than a pH of 5. A pH of 9 is ten times more alkaline (or "basic") than a pH of 8.

What is pH?

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