The correct option is (c).
Explanation
Turmeric is a natural acid-base indicator derived from the Curcuma longa plant. Its active component, curcumin, exhibits distinct colour changes depending on the pH level of the substance it interacts with.
Statement-wise Analysis:
- Statement 1 is Correct: Bases (alkaline substances) react with turmeric to change its colour from yellow to deep red or reddish-brown. This reaction is frequently observed when soap (which is basic) is applied to a turmeric stain on cloth.
- Statement 2 is Incorrect: Acids do not change the colour of turmeric paste. In an acidic medium, turmeric retains its natural yellow colour. It does not turn blue; the blue colour change is characteristic of red litmus paper turning blue in basic solutions.
- Statement 3 is Correct: Neutral substances, which are neither acidic nor basic (such as distilled water), do not alter the chemical structure of curcumin. Consequently, the turmeric paste retains its original yellow colour.
Key Takeaway:
Turmeric acts as a natural indicator that remains yellow in acidic and neutral environments but turns red in basic (alkaline) environments.