Question 9: Sugar is a carbohydrate but does not turn blue-black with Iodine. Why?
Answer: The Iodine test is specific for Starch, which is a complex carbohydrate. Iodine molecules get trapped in the helical structure of starch, creating a blue-black colour. Sugar (Glucose/Sucrose) is a simple carbohydrate with a different structure that does not trap iodine. Therefore, it does not change colour.
Question 10: “All starches are carbohydrates but not all carbohydrates are starches.”
Answer:
- Explanation: Carbohydrates is the main category. It includes sugars (simple carbs), starch (complex carbs), and cellulose (fibre). So, starch is just one type of carbohydrate. Sugar is another type.
- Activity Design:
- Take two samples: Potato juice (Starch) and Sugar solution (Sugar).
- Add Iodine solution to both.
- Observation: Potato turns blue-black (Starch present). Sugar solution does not.
- Conclusion: Both provide energy (are carbs), but only one tests positive for starch.
Question 11: Iodine on socks vs. Saree.
Answer:
- Reason: The teacher’s saree was likely starched (stiffened using starch water, a common practice for cotton sarees). The iodine reacted with the starch on the saree to turn blue-black.
- Mishti’s socks were likely made of synthetic material or cotton that was not starched, so there was no starch for the iodine to react with.
Question 12: Why are millets healthy? Can we eat only millets?
Answer:
- Why Healthy: Millets (Jowar, Bajra, Ragi) are rich in dietary fibre, minerals (Iron, Calcium), and vitamins. They digest slowly, providing steady energy.
- Can we eat only millets? No single food can provide all nutrients in the exact amounts needed. While millets are excellent sources of carbs and minerals, we still need other sources for sufficient proteins (pulses/dairy) and healthy fats. A balanced diet requires variety.
Question 13: How to check if a solution is Iodine?
Answer: To confirm if an unknown solution is Iodine:
- Take a food item known to contain starch (e.g., a slice of raw potato or boiled rice).
- Add a few drops of the unknown solution to it.
- If the food item turns Blue-Black, the solution is Iodine.