CHM026 · Acids, Bases & pH · Classes 5–10
Natural Indicator Color Lab
Objective: To see how natural and laboratory indicators change colour across the pH range.
🧰 Virtual materials and apparatus
- Virtual test tubes at pH 0–14
- Indicators: litmus, turmeric, red cabbage, phenolphthalein, methyl orange
📐 Formulas and SI units
colour from each indicator's change range
💡 Theory
Indicators are dyes whose colour depends on pH. Turmeric is yellow in acids and neutral solutions but turns red-brown in bases. Red cabbage juice shows many colours from red (acid) to yellow-green (strong base). Phenolphthalein is colourless in acids and pink in bases; methyl orange is red in acids and yellow above pH 4.4.
🪜 Guided virtual procedure
- Choose turmeric and set pH 12.
- See the red-brown colour.
- Move the pH down to 7 and below.
- Try red cabbage across the whole range.
- Compare where each indicator changes.
📋 Observations Simulated values
✅ Result and conclusion
Turmeric turns red-brown at pH 12 because the solution is basic.
🔬 Real lab vs simulation
Natural indicator colours vary with how they are made; colours here are illustrative. No extraction or mixing instructions are given.
⚠️ Safety
Do not extract or mix indicators with acids or bases at home; this is a virtual colour lab.
❓ Quick check
1. Turmeric in soap solution turns…
2. Phenolphthalein in acid is…
3. Red cabbage in strong base looks…
🏋️ Practice
EasyLitmus colour in acid?
Answer: Red
MediumMethyl orange at pH 7?
Answer: Yellow
ChallengeWhy are natural indicators useful?
Answer: Cheap, safe colour tests for acids and bases