Can we test everyday items for pH? This is a directed
inquiry on acids and bases using cabbage water as a pH indicator.
In cooperative groups, students test the pH of various solutions.
Note: Label all cups and bottles.
1 qt water.
1 qt water + 1 c baking soda
1 qt water + 1/2 c milk of magnesia
1 qt water + 1/2 c salt
1 qt water + 1 c
1 qt vinegar
1/2 qt lemon juice
1 qt tonic water
1 pitcher cabbage
1 8-oz. cup for each group
8 1-oz. cups for each group
DIVIDE the class into groups of four students
with the following roles:
- Materials Handler: Distributes materials.
- Equipment Handler: Manipulates materials.
- Recorder: Records results.
- Speaker: Shares results with the class.
Have the Materials Handlers PASS out the
following to each group: 1 8-oz. cup of cabbage water; 8 1-oz.
cups, each with a different testing solution.
Have the Equipment Handlers POUR a small
amount of cabbage water into each cup of testing solution. HAVE
the Recorders RECORD the color changes.
Invite the Speakers to PRESENT
their group's results to the class. Have the groups CLASSIFY
the solutions. Then INTRODUCE concepts of acid, base, and neutral
to the class.
ALLOW the class to re-examine their results and determine which
substances are acids, which are bases, and which are neutral.
What's Happening? Find out more about detecting
acids and bases.
Challenge: What happens if two or more of the substances
are combined? Once a solution has become green or pink, can you
make it purple again? Share your results in our pH
Color Me: What
are some other ways to indicate pH, and what colors do they yield?