pH indicators change color depending on the acidity of the substance in which they are placed. The pH scale ranges from 0 to 14. A substance with a pH of 7 is neutral. A pH less than 7 is acidic, and a pH greater than 7 is basic.
The science fair project “Testing pH Levels in Everyday Foods and Household Products” explains pH and acidity. It shows an image of the pH scale and examples of how to test the pH of everyday household items.