Cabbage pH Indicator

INTRODUCTION

In this experiment, you will learn how red cabbage can test if something is basic or acidic. Red Cabbage contains anthocyanin, which is a pigment that can change color when mixed with an acid or a base. An acid is usually described to have a sour or sharp taste, such as vinegar or lemon juice.  A base is usually a cleaning agent in our everyday household such as detergent, soaps, or baking soda.

During this experiment, there will be 4 different items that are commonly found around the house. These 4 items will be mixed with red cabbage juice, that will be made by mixing red cabbage and water, to determine is that item is an acid or a base. The way this conclusion will be determined is by the change in color.  The color will change to a red/pink if the solution is acidic and will change to green or yellow if the solution is basic.

This experiment should be performed in a lab with adult supervision or if you are preforming this at home, in the kitchen with adult supervision.

GENERAL WARNINGS, CAUTIONS, AND DANGERS

  • Do not consume any of the materials used in this experiment.
  • High temperatures will be used during this experiment, do not burn yourself.
  • Wear gloves and safety glasses.
  • Wash hands before and after the experiment.

EQUIPMENT

  • Knife
  • Medium Pot with lid
  • Hot Plate or Stove
  • Funnel (If needed)
  • Oven Mitts/ Hot Hands
  • Labels/ Tape
  • Marker
  • 4 Clear Jars or Small Containers

SUPPLIES

  • 1 Red Cabbage
  • 2 Lemons
  • Baking Soda
  • Vinegar
  • Water

PROCEDURE

Making the Red Cabbage Indicator:

  1. Cut 1 head of red cabbage roughly into small pieces.
  2. Pour 2 cups of water into your medium sized pot.
  3. Place cut red cabbage in your medium sized pot.
  4. Turn stove or hot plate on to medium/high heat.
  5. Place the pot with the cut red cabbage on the stove and boil for 5 minutes.
  6. After the cabbage has been boiling for 5 minutes, take off heat, cover, and let rest for 30 minutes.
  7. Carefully pour the cabbage juice evenly into each of the 5 jars.

Using the pH indicator:

The red cabbage indicator should be dark blue in color to start. The color of the indicator will change to red or pink if the solution is an acid and it will change to green or yellow if the solution is basic. It will remain purple or blue is the test solution is neutral.

  1. Set aside one of your jars and label it “Control”
  2. Label a jar: “Lemon Juice.”
  3. Label a jar: “Baking Soda.”
  4. Label a jar: “Vinegar”
  5. Squeeze half a lemon into the jar labelled “Lemon Juice.” Observe the change in color.
  6. Add a teaspoon of baking soda into the jar labelled “Baking Soda.” Observe the change in color.
  7. Add a teaspoon of vinegar into the jar labelled “Vinegar.” Observe the change in color. (If color did not change, add half a teaspoon until visible color change.)

Disposal:

  1. Dispose of all solid waste in the trash.
  2. All liquids can be disposed of down the drain with plenty of water.

Here are useful videos:

Sources:

American Chemical Society. “Red Cabbage Indicator.” ACS Education & Outreach Activities, American Chemical Society, www.acs.org/education/outreach/activities/red-cabbage-indicator.html.

Little Bins for Little Hands. “Red Cabbage Science Experiment Chemistry.” Little Bins for Little Hands, n.p., n.d., littlebinsforlittlehands.com/red-cabbage-science-experiment-chemistry/.