Question 2 — Sahil placed some pieces of - Questions at the end of the chapter - Chapter 9 Class 7 - Life Processes in Animals (Curiosity)

Last updated at June 1, 2026 by

Q 2
Question

Sahil placed some pieces of chapati in test tube A. Neha placed chewed chapati in test tube B, and Santushti took boiled and mashed potato in test tube C. All of them added a few drops of iodine solution to their test tubes — A, B, and C, respectively. What would be their observations? Give reasons.

🔗 Concept: 9.1.1 Stop 1 — The Mouth

Question 2 — Sahil placed some p - Life Processes in Anim - [Teachoo] - Questions at the end of the chapter
A B C
Three test tubes with iodine test showing different colour results
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A: blue-black. B: no change (or very light blue-black). C: blue-black.

Explanation

  • Test tube A (chapati): Turns blue-black. Chapati contains starch; iodine reacts with starch to give blue-black colour.
  • Test tube B (chewed chapati): No change or very light blue-black. Saliva in the mouth broke down the starch into sugar during chewing — little or no starch remains to react with iodine.
  • Test tube C (boiled mashed potato): Turns blue-black. Potato contains starch; iodine reacts with it to give blue-black colour.
Starch turns blue-black with iodine. Chewed chapati shows less starch because saliva converts starch into sugar in the mouth.
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