Jefferson College of Health Sciences
Arts & Sciences Festival
AN INQUIRY INTO THE EFFECTIVENESS OF ANTACIDS
Purpose:
To compare the effectiveness of over-the-counter antacids using red cabbage extract as a pH
indicator.
Introduction:
If you’ve ever had heartburn or an upset stomach, then you’ve probably used some sort of antacid to
“calm” your stomach. Heartburn is caused by stomach acid refluxing back into the esophagus. The
causes of upset stomachs can vary, but often results when our stomach acid (a mixture of acids called
gastric acid) goes out of control. If we eat too much food (or too much of the wrong kinds of food) our
stomach acid can cause the stomach lining to become irritated.
In this experiment, you will compare the effectiveness of a few common over-the-counter antacids using
red cabbage extract as a pH indicator and lemon juice to simulate the pH of stomach acid. Red
cabbage, along with many other beautifully colored plants, contains a chemical called anthocyanin.
Anthocyanin changes color depending on the pH of a liquid. Since pH is a measure of how acidic a
liquid is, anthocyanin can be used as an indicator of pH.
Research
Question(s):
How do antacids work?
Which antacid is the best for neutralizing acid reflux?
Materials:
6 droppers per group, 4 small test tubes per group, tape and a marker for labeling
Chemicals:
red cabbage extract (red cabbage boiled in water until translucent), lemon juice, various over-thecounter antacids
Procedure:
1. Label the four test tubes with the name of each antacid that you are testing.
2. Use a clean dropper to add ten drops of red cabbage indicator to each test tube.
3. Use a clean dropper to add 10 drops of lemon juice to each test tube. Record your
observations in the table on back of this page.
4. Use a clean dropper to add the first antacid (drop-by-drop) to the first test tube. After each
drop, shake the tube with your finger covering the top and wait. Stop adding drops as soon as
you see a color change. It may take a few minutes to notice a color change. The color change
indicates that the acid has been neutralized. Record the number of drops used in the table
below. Also, record your observations of the color change.
5. Repeat step four with each of the antacids. Don’t forget to record your data for each test!
Do your own exploration at home! Sodas and fruit juices are known to be acidic too! How much
antacid would it take to neutralize a soda? How would you set up this experiment to test the acidity of
the soda? Is soda more or less acidic than lemon juice?
Antacid
Drops of Antacid
Used
Color Observations
Milk of Magnesia
Gaviscon Extra Strength
Equate Maximum Strength
Equate Regular Strength
AN INQUIRY INTO THE EFFECTIVENESS OF ANTACIDS
pg. 2
Instructor notes:
1. The session should begin with an introduction to the pH scale (acid concentration in water).
You can make this relatable to the audience by describing the relative acidity of common
household liquids and chemicals. For example: vinegar, lemon juice, most fruit juices, and
soda are acidic.
2. Next, you will need to introduce pH indicators. Specifically, introduce the red cabbage
indicator. Red cabbage contains a chemical compound called anthocyanin that responds
to changes in pH…it changes color when the pH changes. Now there is a very short demo
that you can do. Red cabbage indicator is available for the instructor along with pH
buffers (pH 3-10). Add about one dropper full of the red cabbage indicator into each
tube containing the buffer solution to show the audience the color change.
3. Introduce the experiment as described above and help the audience collect their own
data to compare antacids. Encourage them to work in groups if you don’t have enough
stations to accommodate everyone.
4. If there is time: encourage the audience to do their own exploration on their own at home.
You can connect this session to one of the activities in the “Bones” session where
decalcification of eggs is demonstrated in vinegar (a household acid). Since our teeth are
bone…what do you are the long-term effects of acid on our teeth?
5. Clean-up and reset for the next session. Everything in this experiment can be dumped
down the sink and tossed in the trash. There are plenty of tubes…so don’t worry about
rinsing out tubes.
AN INQUIRY INTO THE EFFECTIVENESS OF ANTACIDS
pg. 3