pH Scale and Indicators

The pH Scale ACIDS (H+) NEUTRAL BASES (OH-) ------Stronger------ --------Stronger------

INDICATORS INDICATORS are substances that CHANGE COLOR to tell if a substance is an ACID, BASE, or NEUTRAL Examples of indicators are pH paper, red litmus paper, blue litmus paper, and phenolphthalein

LITMUS PAPER Litmus paper comes in two varieties which are RED and BLUE. BLUE litmus will turn RED in an ACID. RED litmus will turn BLUE in a BASE.

LITMUS paper is easy to use LITMUS paper is easy to use. Simply dip the paper into the substance that you’d like to test and observe to see if a color change takes place. This blue litmus paper turned red This red litmus paper turned blue because it was placed in an acidic because it was placed in a base. solution.

While litmus paper is easy to use, it will not tell you the exact pH of the substance you are testing. It will only indicate whether a substance is an acid or a base. To get a more accurate idea of how strong an acid or base is, you will need to use pH paper.

pH PAPER pH paper turns a variety of colors in order to indicate a specific pH number.

Once you dip the pH paper in the substance you would like to test, all you do is match the color to the appropriate color on the pH chart. Each color corresponds to a specific number.

Phenolphthalein Phenolphthalein is a clear, colorless liquid that will turn bright red/pink in the presence of a BASE. It will remain colorless in an ACID or NEUTRAL solution.

NEUTRALIZATION REACTIONS Neutralization occurs when an ACID and BASE are combined in equal amounts. The result is a substance that has a pH of 7. A neutralization reaction results in the production of WATER and SALT.

Neutralization in the Stomach The stomach usually has a pH of about 3 - 4. If it becomes too acidic, the acid can be neutralized by taking a base such as Tums, Pepcid AC, or baking soda which are all bases.

NEUTRALIZATION IN THE SMALL INTESTINES Food moves from the stomach into the small intestines. The stomach is protected from the acids by thick layers of mucus, but the acids from the stomach could damage the small intestines. The pancreas releases an ALKALINE (base) “juice” that will neutralize the stomach acids before it enters the intestines. This “juice” is transported into the small intestines through a duct (tube).