Acid-Base Indicators (page 2)

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Author: Janice VanCleave

Try New Approaches

Anthocyanins are found in red poppies, blue cornflowers, grapes, beets, blueberries, and apple skin. Repeat the experiment using a different plant and/or fruit to make anthocyanin indicator. How do the colors differ from the colors in the original experiment?

Design Your Own Experiment

  1. In the original experiment using red cabbage indicator, only three different testing materials were used. Thus, a pH color scale for the indicator would look like Table 27.2.
  2. If you have access to a pH meter, design a pH color scale for red cabbage indicator and/or other food or plant indicators. With assistance from an adult, use an acid stronger than lemon juice or vinegar and a base stronger than ammonia to create a color pH scaled from 0 to 14. As you add drops of acid or base to the indicator, test the liquid's pH, then record the pH and color until you\ have determined colors for pH 0 to 14.

Get the Facts

The color of some flowers is an indication of the pH of the soil they grow in. Hydrangeas have pink flowers in soil with a high pH (basic) and blue flowers in soil with a low pH (acid). Find out more about soil pH by checking with a plant nursery, school agriculture department, or county agriculture department for information. What can be added to soil to change its pH? Science Fair Hint: Determine the range of colors of flowers containing acid-base indicators. Do this by growing plants, such as hydrangeas, in soils of various pH. Your control can be soil with a pH of 7.

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