Acids and Bases

Acids and Bases

This interactive tutorial will take you through such concepts as dissociation, proton donors, proton acceptors, alkalinity, and more. So don’t be neutral — hop on the pH scales, touch all the bases, and don’t drop any acids!


Within a quantity of liquid water, some molecules tend to break up or dissociate. For pure water, a very few molecules will dissociate into a hydroxide ion (OH-) and a hydrogen ion (H+).


Acids are molecules that dissociate in water and release a hydrogen ion (H+) and a negatively-charged anion. Alternately, since a hydrogen ion consists solely of a proton, acids can also be defined as proton donors.

Acid solutions have a sour or sharp taste and have a pH less than 7.

A strong acid has a very low pH (0-4) and a weak acid usually has a higher pH (3-6).

Bases or Alkalines

Molecules that dissociate in water and release a hydroxide ion (OH-) and a postively-charged cation are called bases or alkalines. Some bases do not dissociate, but instead bond with a hydrogen ion (H+) to form a new molecule. Thus, bases can also be defined as proton acceptors.

Bases have a flat taste and are slippery in an aqueous solution, with a pH greater than 7.

A strong base has a very high pH (11-14) while a weak base has a lower pH (8-10).

pH Scale

In mathematical terms, pH is defined as the negative base-10 logarithm of the molar hydrogen ion concentration. In simpler terms, pH describes the acidity or basicity (alkalinity) of a solution.

Zero on the pH scale is the strongest acid, while 14 is the strongest base. Water, which is neutral, has a pH value of 7.

As you move up on the scale, each value has ten times the amount of OH-; moving down the scale has ten times the H+. The values are measured in terms of moles/liter of hydrogen ions.

Litmus Test

Litmus is an organic dye extracted from certain lichens and is used to test a solution for its concentration of hydrogen ions (acid or base). The litmus paper is naturally pink in color and changes to red in the presence of acids and blue in the presence of bases.

The pH scale is often colored with a red to blue gradient representing the colors from the litmus test.