This scale measures how acidic or basic a substance is. A substance that is neither acidic nor basic is considered neutral. An acid or base can be made neutral by mixing it with it's opposite. The pH scale is also logarithmic in that each whole number change is ten times more acidic or basic. For example, pH 8 is ten times more basic than pH 7 and pH 9 is one-hundred more times basic than pH 7.
Pure water is the center of the scale and is considered neutral.
The center of the scale is pH 7. Acids and bases are often mixed with water and therefore make the water acidic or basic. The resultant values fall within the range of 0 to 14 and are much easier to represent than actual hydrogen concentrations. The pH Applet will describe the levels of the pH scale and some common items with there pH values.