A pH scale is used to measure how much or how little acid is in a substance. Values range from 1 to 14, and lower pH values carry the highest levels of acidity.
To give you an idea of how the scale can be used, water has a pH value of 7, while battery acid has a pH value of 1. If a food or drink has a pH value closer to 1 than 7, you may run the risk of destroying your tooth enamel. Tooth enamel is the hardest substance in the human body, even harder than your bones!