Activity 2.1 Let us explore Table 2.1 Testing the nature of samples with blue and red litmus papers Class 7
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Activity 2.1 Let us explore Class 7
Activity 2.1 Let us explore (Pages 8-9) Class 7
Answer:
Table 2.2 Grouping of samples tested in Table 2.1 Class 7
Answer:
| Group A | Group B | Group C |
| Lemon juice, amla juice tamarind water vinegar orange juice | Soap solution, baking soda solution, lime water washing powder solution | Tap water Sugar, solution, Salt solution |
Observation and conclusion:
- Substances in Group A, are acidic as they turn blue litmus paper red.
- Group B substances are basic as they turn red litmus paper blue.
- Group C substances, are neutral because they do not change the litmus paper colour.
Question 1.
What are these red and blue litmus paper strips made of? Why do they change colour when drops of some samples are put on them?
Answer:
Red and blue litmus paper strips are made from a natural substance obtained from lichens. They change colour when they come in contact with acidic or basic substances.
Question 2.
Do you find lichens on trees in your neighbourhood?
Answer:
No, I have not seen the lichens in our neighbourhood, but found them growing on trees, when I was in Mandi (Himachal Pradesh) with my parents.