What Is the pH Scale? — Definition & Overview

(Video) pH and pOH: Crash Course Chemistry #30

by CrashCourse

This video by Crash Course explains the math behind the pH (and pOH) scale. With this information, you'll be able to understand what this scale actually measures, why water has a pH of $7$, and also what all of this looks like in terms of numbers.

The pH Scale

What is the pH scale?

• The pH scale is a scale used to measure the pH (acidity or basicity) of a solution

• The pH of a solution can range from 0 (very acidic) to 14 (very basic/alkaline), with a level of 7 being neutral (neither acidic nor basic)

• Acidic substances have a larger concentration of hydrogen ions (H$^+$)

• Basic/Alkaline substances have a larger concentration of hydroxide ions (OH$^-$)

How is pH measured?

• pH is typically measured using pH paper, which when dipped in the solution, will change color to indicate a certain pH (take lemon juice for example, when pH paper is dipped in lemon juice, the color changes to red, indicating it is acidic)

• Other methods of measuring pH include pH colorimeters and indicators