Could you suggest various materials which can be used for writing the message on the white sheet of paper (given at the beginning of the chapter) and what could be in the spray bottle? Make a table of various possible combinations and the colour of the writing obtained.
Various combinations of writing materials and spray bottle contents can be used to reveal hidden messages:
| Writing Material | Spray Bottle Content | Colour of Writing |
|---|---|---|
| Soap solution | Turmeric solution | Reddish-brown |
| Baking soda solution | Turmeric solution | Reddish-brown |
| Lime water | Turmeric solution | Reddish-brown |
| Lemon juice | Red rose extract | Red |
| Vinegar | Red rose extract | Red |
| Soap solution | Red rose extract | Green |
| Baking soda solution | Red rose extract | Green |
The principle is that the writing material (acidic or basic) reacts with the indicator in the spray to produce a visible colour change, revealing the hidden message.
Explanation
The chapter begins with a scenario where words appear on white paper when a liquid is sprayed. This demonstrates the use of acid-base indicators. Turmeric paper turns red in basic solutions, while red rose extract gives red colour in acidic solutions and green in basic solutions. By using basic substances (soap, baking soda, lime water) for writing and turmeric for spraying, or using acidic substances (lemon juice, vinegar) for writing and red rose extract for spraying, hidden messages can be revealed through colour changes.