What is pH?

Although you may hear the term thrown about frequently, few people actually have an in-depth knowledge of just what pH is. Affecting nearly every solution in the world around us, pH has an impact on everything from the weather to personal health. However, the answer to the question, “What is pH?” is not nearly as complicated as its effects. Essentially, pH is a measurement of the concentration of hydrogen ions in solutions. What pH is an abbreviation of is the phrase “potential of Hydrogen.”

Ranging from values of 0 to 14, what pH is used to measure is the acidity or alkalinity of a substance; that is, how acidic or how basic (caustic) it is. A score of 7 is perfectly neutral, while numbers below 7 are acidic, and numbers above 7 are basic. Although there may not seem to be much difference between the numbers, what the pH of a substance is can make a huge impact. For example, human blood has a pH between 7.35 and 7.45, and even a tenth of a variation outside of this range can result in death. Further, the body’s pH being off can result in numerous health problems.

So, just what is pH technically? Well, a liquid with a pH of 4 would have 1 x 10-4 moles of hydrogen ions. A pH of 10 means the solution has 1 x 10-10 grams of hydrogen ion (for hydrogen, 1 mole is the same as 1g/L). In the most technical sense, the answer to “What is pH?” is: pH is the negative logarithm of the concentration of the hydrogen ion in a substance. However, in laymen’s terms, what pH is meant to measure is simply the acidity or alkalinity of a substance.