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Q6 (Difficult): Could you suggest various materials which can be used for writing the message on the white sheet of paper and what could be in the spray bottle? Make a table of various possible combinations and the colour of the writing obtained.
Answer:
We have studied that
acidic
and
basic substances
react with
indicators
to produce
colour changes
. This is why invisible writing becomes visible.
💡 Materials for Secret Writing:
| Writing Material | Spray Bottle Content | Colour Obtained |
|---|---|---|
| Lemon juice (acidic) | Baking soda solution (basic) | Brown/Yellow |
| Orange juice (acidic) | Soap solution (basic) | Light brown |
| Vinegar (acidic) | Lime water (basic) | Yellowish |
| Onion juice (acidic) | Washing powder (basic) | Brown |
| Turmeric solution (basic) | Vinegar (acidic) | Red |
Conclusion: Acid-base reactions create visible colour changes.
