One of the oldest indicators is litmus, a vegetable dye that turns red in acid solutions and blue in basic ones. Other indicators include alzarin, methyl red, and phenolphthalein, each one being useful for a particular range of acidity or a certain type of chemical reaction. In the performed experiment, the red cabbage extract was used as an indicator. The color of any material is due to the chemical makeup of the substance that affects the light waves absorbed and reflected. Bases change the chemical structure of the cabbage so that it reflects more green light waves.
Acids change the structure of the cabbage so that it reflects more red light waves.
These specific changes allow red cabbage to be used to indicate the presence of an acid or a base. The experiment performed presented a means by which I was able to determine whether a common household product or food was an acid of a base. Hence, acids and bases occur commonly in our everyday lives. In a broader view, this understanding of the characteristics of acids and bases supports the notion that chemistry is universal and exists to facilitate lives. Copyright 1994 Microsoft Corporation.