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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.
š” 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.
Q12 (Medium): Observe and analyse the information given in the following flowchart. Complete the missing information. Imagine a garden with plants showing signs of poor health. The soil can be ______ in nature. Which indicator can be used to test the nature of the soil? The acidic soil can be treated with ____. The basic soil can be treated with ____.
Answer:
We have studied that
soil pH
affects
plant growth
and can be
corrected
using
neutralisation
. Based on the science:
š” Complete the flowchart:
- Soil can be acidic or basic in nature
- Litmus paper can test soil nature
- Acidic soil treated with lime (basic)
- Basic soil treated with organic matter (acidic)
