Explore Air

Acid Rain Lesson Plan

pH Scale

  • As mentioned above, the pH scale ranges between 0 and 14, with 7 being neutral (Figure 1). A substance with a pH less than 7 is acidic. If greater than 7, the substance is basic or alkaline.
  • Each one-unit change in pH is a tenfold increase or decrease in the strength of the acid or base being measured.
  • A unit change from pH 5 to pH 3 would be a hundred times (10 x 10) increase in acidity.

updated on 04/24/2006  I   http://www.nature.nps.gov/air/edu/Lessons/pHScale.cfm   I  Email: Webmaster