The Basics of pH

pH is a mysterious term that many people use without understanding what it actually means. Everyday Einstein helps unmask this confusing term.

Lee Falin, PhD
4-minute read
Episode #5

The pH Scale

Anything that increases the amount of hydrogen ions when dissolved in water is considered an acid. Anything that decreases the amount of hydrogen ions is considered a base. The pH value of a substance is determined by just how much it changes the amount of hydrogen ions.

Since the pH scale is a logarithmic scale, this means that something with a pH of 4 is 10 times more acidic than something with a pH of 5 and one hundred times more acidic than something with a pH of 6. Likewise, something with a pH of 9 is ten times more basic than something with a pH of 8 and a hundred times more basic than something with a pH of 7.

pH Indicators

A fun experiment that you can do at home is to measure the pH of different substances. While most of us used Litmus paper in school to test pH, many substances that occur in nature can act as pH indicators, usually by changing color.

For example, hydrangea bushes will produce blue flowers if the soil they are grown in has a pH of 5.5 or lower, pink flowers in a soil with pH of 6.5 or higher, and either purple or a mix of pink and blue if grown in soil with a pH between 5.5 and 6.5. Red cabbage is another pH indicator that you can use at home.

If you don’t like the smell of boiling cabbage, you can usually find pH indicator strips at your local aquarium supply store or online. (These are my personal favorites.)

Since the concentration of hydrogen ions also affects how well a solution conducts electricity, you can also find electrical pH testers. However some of the cheaper instruments are notorious for being inaccurate.


That’s all the pH fun for this week. Next week, we’ll talk more about the special qualities of acids and bases.

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Please note that archive episodes of this podcast may include references to Everyday Einstein. Rights of Albert Einstein are used with permission of The Hebrew University of Jerusalem. Represented exclusively by Greenlight.

About the Author

Lee Falin, PhD

Dr. Lee Falin earned a B.S. in Computer Science from the University of Illinois, then went on to obtain a Ph.D. in Genetics, Bioinformatics, and Computational Biology from Virginia Tech.