At Home Red Cabbage pH Indicator

Make your own red cabbage pH indicator

Red cabbage pH indicator is an easy and safe substitute to chemical pH indicators that can be made at home.

Materials:

Red Cabbage Indicator:

• Red cabbage

• Knife

• Blender

• Strainer

• Distilled water (preferred) or tap water.

Instructions:

Start by cutting the cabbage into strips. Add the cabbage and one cup (or 200 mL) of water into the blender. Blend the water and cabbage and then strain the mixture, saving the liquid.

Adjust the amount of water accordingly. You will need roughly 5 mL of indicator per test.

Use your red cabbage pH indicator

Materials:

• Red cabbage pH indicator from above

• Three small beakers (200 mL) or clear plastic cups.

• Measuring spoons

• Baking soda

• Vinegar

• Extension: Other substances for testing such as lemon juice, milk and ammonia.

Instructions:

• Cup One: Mix a half cup (150 mL) of water and two tablespoons (about 30 mL) of vinegar.

• Cup Two: A half cup (150 mL) of water.

• Cup Three: Mix a half cup (150 mL) of water and a tablespoon (15 mL) of baking soda.

Stir Cup One and Cup Three. Be sure to use a different stirrer and do not cross-contaminate the cups!

Add a half teaspoon (or 2.5 mL) of red cabbage pH indicator to each cup and observe.

Results:

The cup with baking soda will turn blue, the water cup will turn violet and the vinegar cup will turn red. There may be slight color variations based on the type of water used in the pH indicator and the water used in the cups.

The chart below pairs the pH range with colors you will observe using a red cabbage indicator.

Approximate pH Range

1 to 5: Red/pink (More Acidic)

6 to 7: Violet

8 to 9: Blue

10 to 11: Blue/green

12 to 14: Green (More Basic)

Background Information:

pH is a measure of hydrogen ion concentration of a solution. The pH range is measured from 1 – 14. A pH of 7 indicates a neutral substance where there are equal hydrogen and hydroxide ions. A pH lower than 7 indicates an acid with a higher hydrogen ion concentration and a pH higher than 7 indicates a base with lower hydrogen ion concentration.