This lab activity uses red cabbage juice as a pH indicator to test common household liquids and determine their pH levels. Red cabbage juice contains the pigment flavin, which changes color depending on the pH of the solution. Students will mix red cabbage juice with various household liquids and observe the color change, then use a reference table to identify the approximate pH. They will also mix an acid and base together and observe the resulting change, recording their observations and conclusions.

1. Name __________________________________________________________________________
Date _______________________________ Group _________________________________
Lab Activity “ pH Indicator= Red Cabbage juice”
Introduction:
The nomenclature pH means “the potential of hydrogen” and refers to the ability of a
chemical to donate or accept hydrogen ions to other chemicals. Acids donate
hydrogen ions while bases can accept them.
In this lab, you will use the juice from red cabbage as a pH indicator to test common
household liquids and determine their pH levels. Indicators are substances that readily
change their color due to changes in pH. You will mix cabbage juice with different
household liquids and see a color change produced by a pigment called flavin (an
anthocyanin) in red cabbage. Through this color change, you will be able to
successfully identify the approximate pH of common household liquids using the table
below:
Method:
1. Pour 10 ml of red cabbage juice into a test tube
2. Pour 10 ml of the substance to its respective test tube and mix
3. Observe color change and record results in the Result Chart
4. Mix an acid with a base and observe changes. Record your results.
Results:
Chemical Color Change pH Acid or Base
Describe you observations, results and conclusions:
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Questions:
1.- What is an acid-base indicator?
2.- What is the name of the pigment present in red cabbage?
3.- Using your results, create a color-coded pH scale.
4.- Besides litmus and red cabbage juice, mention 3 substances that can be used as an
acid-base indicator.
3.- What happens to the pH when a base is added to an acid?

2. 4.- Whenever you mix an acid with a base, they neutralize each other. If
this is the case, why is an antacid used to treat stomach aches?