Paheli Boojho Chapter 6 Class 7 Science Physical and Chemical Change:
1. We learnt in Chapter 1 that plants produce their food by a process called photosynthesis. Can we call photosynthesis a chemical change?
Answer: Yes, photosynthesis is a chemical change. Here, plants utilize the energy of the sunlight and convert atmospheric carbon dioxide into food substances. Here a new substance “glucose” is formed and oxygen gas is liberated as a by-product.
Carbon dioxide (CO2) + Water ——–> Glucose (C6H12O6) + Oxygen (O2)
2. Paheli’s remark seeks an explanation for why people in coastal areas complain about rusting of iron particles.
Answer: Iron articles like Almira, kneel, stove etc react with atmospheric oxygen in the presence of moisture or water and form brown iron oxide. This process is called rusting. Coastal areas contain a high amount of moisture in their environment, so iron particles in coastal areas catch rising faster than other areas.