Name:__________________________ Period: 1 2 3 4 5 6 7 Date:____________________
Red Cabbage
Chemistry
Introduction:
Liquids all around us have either acidic or basic (alkaline) properties. For example, acids taste
sour while bases taste bitter and feel slippery. However, both strong acids and strong bases can
be very dangerous and burn your skin, so it is important to be very careful when using such
chemicals. In order to measure how acidic or basic a liquid is, one must use the pH scale as
shown below:
The strength of the pH scale is determined by the concentration of hydrogen ions (H+) where a
high concentration of H+ ions indicate a low pH and a low concentration of H+ ions indicate a
high pH. The pH scale ranges from 1 to 14 where 1 to 6 is classified as acidic, 7 neutral (neither
basic nor an acid) and 8 to 14 is classified as basic. This explanation helps us understand why
pH stands for “potential hydrogen.”
Remember that pH is a chemical property and as with all chemical properties it can’t be observed
but it has to be tested to be known. 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. You will mix cabbage
juice with different household liquids and see a color change produced by a pigment called flavin
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.
Color
Pink
Dark Red
Violet
Blue
Blue-Green
Approx. pH
Acid/Base
1-2
Acid
3-4
Acid
5-7
Acid/Neutral
8
Base
9-10
Base
GreenYellow
11-14
Base
Liquids to Test/Predictions:
Fill in the list below with the liquids we will be testing today. You will also need to predict
whether each liquid is an acid or a base.
Name of
Substance
Prediction
Acid or
Base
Lab Instructions:
1. You will need approximately 25mL of red cabbage juice for each of the 8 liquids that you will
be testing. This means that you will need 200mL of cabbage juice for all 8 of your tests.
2. For each liquid that you are testing you will take 50 mL of the liquid that you are testing and
add it to 25mL of the cabbage juice indicator. You will need to stir each sample thoroughly to
make sure that the two liquids mix.
3. There might be some solids that your teacher wants you to test so you will need to mix these
solids into water before testing their pH. (For example you might test out baking soda by adding
three tablespoons of baking soda to 25mL of water)
4. Please leave out each sample so that you can compare them to one another and estimate their
overall pH level. After you have estimated their pH levels put them in order from most acidic to
most basic like an actual pH scale.
Experiment Results:
Name of Substance
Color Change
Predicted pH
Actual pH
Real Life Applications:
1. Neutralization occurs when you mix an acid with a base, they neutralize each other. If this is
the case, why is Alka-Seltzer used to treat stomach aches? (Excess stomach acids cause stomach
aches)
2. What is acid rain, how does it form, and how does it negatively impact environments such as
oceans, rivers, lakes, and ponds?