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pHun with Red Cabbage

Did you know that you can determine the pH properties of some liquid substances using cabbage leaves?  Yes! Determine if your pH is acidic, neutral, or basic all by the colors your cabbage solution turns.

 The students will determine the pH level of different substances by observing the reaction of the acid-base indicator present in cabbage juice.

This can get messy as cabbage juice will stain! It should be advised that students should wear old clothing or suggest that students bring an old t-shirt to wear over their clothes if you don’t have smocks available for use.

You may also want to make the cabbage solution prior to students joining the activity.

• Red Cabbage

• Blender

• Strainer

Each Group will need:

• Clear Glasses, or Clear Plastic Cups (for each substance you plan on testing)

• White Paper

• ‘pH’un with Red Cabbage Worksheet

Substances to test:

• Vinegar

• Baking Soda

• Sugar

• Shampoo

• Aspirin

• Lemon Juice

• Detergent (Laundry or Dish)

• Table Salt

• Clear Soda such as Sprite

• Milk

How to Make the Cabbage Solution:

1. In the Blender, blend together 2 Cups of Red Cabbage to 1 Cup of Water

2. Strain the liquid from the cabbage bits. Divide this liquid between the clear glasses that will be using to test your substances.

3. You may need to repeat these steps to make enough for your class, depending on how many groups you have. (Groups will need about 1tsp of red cabbage juice for each substance they test.)

Activity:

1. Pass out the pHun with Cabbage worksheet to students.

2. Demonstrate to the students: A good idea is to test a substance that is acidic and a substance that is basic to show students. The acidic reaction will be red and the basic reaction will be green.

3. Begin your demonstration with vinegar. Pour about ½ cup of vinegar into a cup. Add 1 tsp of cabbage juice to the glass. Observe the color change with students. Vinegar is acidic and the color in the glass will be red.

   1. What color did the liquid turn?

   2. Using the table on the pHun with Cabbage worksheet determine if vinegar is acidic or basic.

4. Repeat these steps with laundry detergent. Detergent is a basic and your liquid will turn green. Keep these two samples as reference for your students.

5. Have students in their groups test the other substances with the cabbage juice.

6. Have students record their observations of each substance in the chart of their worksheet. Students should determine the color of the liquid substance after it reacts with the cabbage juice. From this observations students should then fill out the chart on their worksheet with the approximate pH based on color, and if the substance is an acid, neutral or base in the appropriate columns of the chart.

Introduce a head of Red Cabbage to the students.

Talk about the nutritional value of red cabbage: high in vitamin A and C and shows some anti-bodies for preventing cancer.

One of the most popular ways to enjoy red cabbage is in the popular side dish, coleslaw.

Ask students- Which substance was the most acidic?

Which substance was the most basic? Were they surprised by any of the results?

Wrap up lesson with the nutritional benefits of red cabbage.