pH scale and indicators
Acids, Bases and Salts (School Level) · Chemistry
Study notes
A student tests three solutions with blue litmus paper and pH paper: (A) lemon juice, (B) distilled water, (C) soap solution. Predict results. Step 1: Lemon juice is acidic (citric acid) → blue litmus turns red; pH ~2–3. Step 2: Distilled water is neutral → no litmus change; pH = 7. Step 3: Soap solution is basic → blue litmus stays blue (red would turn blue); pH ~9–10. Conclusion: litmus tells acid vs base; pH paper gives the exact value.