SC 130 Physical Science laboratory 13: Floral pigments as litmus tests for acids and bases
This laboratory explores the use of floral and leaf pigments to whether a substance is an acid, bases, or neutral.
This section of the laboratory explores whether flower petal pigments are good indicators of acids and bases,
and if so, which flowers work best. To produce our flower petal test solutions the petals will be boiled in water.
In the English language acids are said to be sour or tart. Bases are often said to be bitter.
There are three phases to this laboratory.
- In the first phase you will gather flowers to use as tests for whether a substance is an acid or base.
Pick common flowers. Do not pick flowers that belong to someone. Do not pick the orchids in front of the
library or other rare flowers. You might also try colorful leaves, again, avoiding rare plants.
- In the second phase you will determine which flower produces the best floral fluid for determining whether something
is an acid, base, or neutral. After boiling the petals, the fluid will be tested with a known acid and a known base.
You are looking for a flower fluid which shows a distinct and different color change for known acid and the known base.
In this lab lime juice is our known acid and baking soda is our known base.
- In phase three you will use that one "best" flower fluid to test liquids to determine if they are an acid,
base, or neutral. When working with test tubes, be sure to rinse them well between tests. Be careful, some unknowns are
poisonous, others can burn your skin.
Make a table [d][t][a] of your results for the unknowns noting the color change and the conclusion
(acid, base, or neutral).
Use a flower petal solution that changes color in a consistent way for acids or bases.
Use the solution to analyze [a] whether the following are acids or bases
(additional compounds might be made available on lab day):
- baking powder
- corn starch
- diluted bleach
- drain clog dissolvers
- mineral lime (coralline lime)
Discuss what flowers showed the most distinct color change for the known acid.
Discuss what flowers showed the most distinct color change for the known base.
Discuss any difficulties you encountered.
Discuss any sources of potential error.