Mysterious Solutions

Can we test everyday items for pH? This is a directed inquiry on acids and bases using cabbage water as a pH indicator. In cooperative groups, students test the pH of various solutions.


Materials

Note:
Label all cups and bottles.

1 qt water.

 


1 qt water + 1 c baking soda

 


1 qt water + 1/2 c milk of magnesia


1 qt water + 1/2 c salt

1 qt water + 1 c sugar


1 qt vinegar

 


1/2 qt lemon juice

 


1 qt tonic water

1 pitcher cabbage water


1 8-oz. cup for each group


8 1-oz. cups for each group

 


What To Do

DIVIDE the class into groups of four students with the following roles:

  • Materials Handler: Distributes materials.
  • Equipment Handler: Manipulates materials.
  • Recorder: Records results.
  • Speaker: Shares results with the class.



Have the Materials Handlers PASS out the following to each group: 1 8-oz. cup of cabbage water; 8 1-oz. cups, each with a different testing solution.

 

 

 


Have the Equipment Handlers POUR a small amount of cabbage water into each cup of testing solution. HAVE the Recorders RECORD the color changes.

 

 

 


Invite the Speakers to PRESENT their group's results to the class. Have the groups CLASSIFY the solutions. Then INTRODUCE concepts of acid, base, and neutral to the class.

ALLOW the class to re-examine their results and determine which substances are acids, which are bases, and which are neutral.

What's Happening? Find out more about detecting acids and bases.

Challenge: What happens if two or more of the substances are combined? Once a solution has become green or pink, can you make it purple again? Share your results in our pH Exchange.

Color Me: What are some other ways to indicate pH, and what colors do they yield? 

 


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