Red Cabbage Indicator Lab
The objective of this lab is to determine the approximate pH of household solutions by using a red cabbage as an indicator solution.
A red cabbage contains a pigment molecule that is called flavin. When placed in very acidic solutions, the anthocyanin in the flavin will turn a reddish color. In neutral solutions, the color stays purple. In basic solutions, the solution will turn greenish-yellow. The color of the solution changes in response to the changes in the hydrogen ion concentration. The equation for pH is pH=-log[H+]. A pH indicator measures whether a substance, usually a liquid, is acidic or basic. When the indicator comes in contact with the substance, the indicator’s color corresponds to the substance’s approximate change.
If I test the pH of household items with the red cabbage, then the solution will undergo a physical change.
Household Liquid | Color Guess | Approximate pH Guess |
Apple Cider Vinegar | Purple | 3 |
Mouthwash | Green | 9 |
Baking Soda | Green | 11 |
Cream of Tartar | Red | 2 |
Detergent | Violet | 6 |
Lemon Juice | Red | 2 |
Denture Cleaner | Blue | 8 |
* (1) Red/Purple Cabbage
* Boiling Water
* Large Container
* 7 Bowls or Cups
* Lemon Juice
* Apple Cider Vinegar
* Cream of Tartar
* Baking Soda
* Denture Cleaner Tablet
1. Cut and dice about half of the cabbage and place into a pan with water.
2. Heat the water until it boils and creates a purple liquid.
3. Strain the cabbage and place liquid in a container.
4. Label the 7 cups/bowls with the liquid you will place in it. (Ex: Vinegar, Lemon Juice, etc.)
5. Pour about ¼ cup of each liquid into the respective cup except for the cream of tartar, and the baking soda.
6. For the baking soda, add about a spoonful of water to the powder and mix...