9/29: Acids, Bases, and Red Cabbage Juice

Activity: Red Cabbage Indicator

Materials:

Red cabbage juice (purple color)

Disposable glass test tubes

Plastic dropper bottles

Test tube racks

A variety of liquids of varying pH. We will use: lemon juice, vinegar, water, baking soda solution, soapy    water, and toothpaste solution

Safety Concerns: Make sure the students know they should not eat or drink anything in this activity, nor should not touch their faces at anytime (to avoid ingesting liquids or getting their in their eyes). Have students wash their hands promptly after clean up.

Procedure:

1. Discuss acidity, basicity and pH as above.

2. Give each pair of students a test tube rack with eight test tubes, each filled about 1/3 of the way with indicator solution

3. Allow the students to experiment by adding the different liquids to the test tubes. Remind them that they only need a few drops to cause a color change. They should be able to tell which solutions are acidic and which are basic.

4. Have students fill out the following data table.

Data Table

Solution

Color Before Mixing

Color After

Mixing

Acidic, Basic or Neutral?

Other Observations

Lemon juice

Water

Soapy water

Baking Soda

Vinegar

Sprite

Toothpaste

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