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Cabbage Juice pH Indicator

  • Introduction
  • Video
  • Materials
  • Procedure
  • Advanced Preparation & Notes
  • Downloadable Files

pH Indicators

pH stands for “power of hydrogen” and is reflection of how much H+ is in a solution.   It is the number scale (a logarithmic one) from 0 to 14 that describes whether something is acidic or basic.  A pH of 7 is considered neutral.  Less than pH 7 (0-6) is an acidic substance and greater than pH 7 (8-14) is basic.  A pH Indicator changes color when mixed with acids and bases.  The purple pigment in purple cabbage can be red or pink if it is mixed with an acid.  It will turn blue-green or even yellow when mixed with bases.

cabbagetable

dixiecups_ph

 

Basic home demonstration of the experiment.

 

 

 

 

Materials - Cabbage juice indicator

Making cabbage juice

  • Purple cabbage
  • blender  
  • Coffee filters
  • Funnels
  • Cup or bowl to filter juice (Ball glass jars are fine)
  • Small dixie cups
  • Solutions of known pH or
    Table of known colors

Test solutions

  • vinegar
  • lemon juice
  • baking soda
  • 409 or windex
  • seven-up or diet coke

Indicator Stirring Demonstration

  • stir plate
  • stir bar
  • universal indicator or cabbage juice
  • 0.1 M NaOH

Make your own pH indicator
1.  Take a cup the cabbage/water mixture.
2.  Filter through a coffee filter into a cup.

This purple juice contains pigments (colored compounds) from the cabbage.  The color of these pigments is sensitive to the presence of acids and bases.


Test the pH of common liquids.
1.  Pour a small amount (1/4 full) of your cabbage juice into a  Dixie cup.

2.  Add drops of one of the test solutions and swirl.  Add until there is a color change.  What is the final color of this solution?  Compare it to the color chart or standard solutions.  Is it an acid or a base?

3.  Repeat with the other test solutions.

 

Notes

  • For the highest pH (yellow color), oven cleaner can be tested but this should be handled by an adult with eye protection and gloves.
  • This procedure does not boil the cabbage leaves and works fine.
  • If the coffee filters are dried, they can be cut up and taken home for use as pH strips.