. [ U s i n g P l a n t s A s p H I n d i c a t o r ] .

Introduction:

Plants, especially flowers, are of great diversity of colours. The colour of plants is due to the presence of certain pigments such as chlorophylls and carotenoids. These pigments are subject to the change of pH, that means, they show different colours at different pH.

For example, the purple colour of the red cabbage will turn red when acidic solution is added while it will turn blue, green or yellow when added upon an alkaline solution.

Materials:

  1. Red cabbage
  2. Dilute hydrochloric acid
  3. Dilute sodium hydroxide
  4. Vinegar
  5. Soda water
  6. Washing powder solution
  7. Baby shampoo

Procedure:

  1. Immerse a few leaves of red cabbage in boiling water to soften them.
  2. Squeeze some juice (purple) from the leaves into a beaker.
  3. Transfer some of the juice into two test-tubes. This may act as a pH indicator.
  4. Add several drops of dilute hydrochloric acid into one test tube and sodium hydroxide into another.
  5. Observe the colour change.
  6. Repeat this experiment with different test solution such as vinegar, washing powder solution, soda water, baby shampoo, etc.