Lab: Cabbage Juice as a pH Indicator?
Introduction
A pH indicator is a substance that has a different color when added to acid or alkali. In this experiment a pH indicator is
made from red cabbage. Red cabbage juice when neutral is a purple color. When placed in an acid it turns one color
and in a base another color. It is a very good indicator of acids or bases.
Safety Precaution: You should wear some sort of eye protection to do this lab: Safety Goggles, Prescription glasses or
even Sunglasses to prevent splash or glass projectile.
Purpose
To make an acid base indicator from a common piece of produce.
To identify acids and bases in common items found in the home using an indicator
Materials
Red Cabbage
coffee filter paper, cheese cloth, paper towel or hand towel
1 jar/bowl
1 Spoon
4 glasses
5 or more of the following: white vinegar, baking soda, ammonia/Windex, table salt, milk, lemon juice, milk of
magnesia, toothpaste, shampoo, carbonated beverage, bleach* or other common household products
* Use of Safety Goggles/Sunglasses is advised while using glass and or bleach. Use proper precaution while handling
bleach – refer to instructions on the bottle.
Procedure:
1.
Heat up 2 cups of water in a jar or a bowl
2.
Chop up about ¼ of the cabbage and put chopped red cabbage leaves into hot water.
Crush the leaves with a spoon. Continue this process until the water has a distinct
color.
3.
Strain the mixture through a piece of clean filter paper (or cheese cloth or paper towel) into a clean jar. The
liquid that collects in the jar is your indicator.
4.
Label 5 glasses white vinegar, baking soda, ammonia, table salt, milk, lemon juice, milk of magnesia,
toothpaste, shampoo, and carbonated beverage. (Permanent marker can be scrubbed off with a scrub/sponge)
5.
Pour the cabbage juice indicator into each glass to a depth of about 1 cm.
6.
Add several drops of each of the samples to the glasses containing the indicator. Record the color of all the
samples in a data table along with a description of the sample tested.
Data:
Acid/Base Samples Tested
Sample Tested
Color of Cabbage Juice
Picture: Please include the picture of your results.
Analysis:
1. Determine whether each sample is an acid or a base and record in a data table
Questions:
1. What color is the cabbage indicator when neutral? . . . when basic? . . . acidic?
Neutral
Basic
Acidic
2. Describe how the color of the red cabbage juice indicator changes as you move from
highly acidic to highly basic solutions. Note any color patterns that you observe.
3. Is cabbage juice a good indicator of pH? Why or why not?
Approximate pH