NCERT Solutions for Class 7 Curiosity Chapter 2 Exploring Substances: Acidic, Basic, and Neutral Page No. 10 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 paper soaked in an extract of lichens. They change colour when they come in contact with acidic or basic substances. Acidic substances turn blue litmus to red, and basic substances turn red litmus to blue. Question 2. Do you find lichens on trees in your neighbourhood? Answer: Yes, lichens can be found growing on trees, especially in areas with clean air and good rainfall. Question 3. If litmus is not available, are there some other natural substances that can serve as acid- base indicators? Answer: Yes, there are other natural substances that can be used as acid-base indicators, such as red cabbage juice, turmeric, and rose extract. These substances also change colour in the pr...
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