Question 9 — Yadu conducted an experiment to - Questions at the end of the chapter - Chapter 9 Class 7 - Life Processes in Animals (Curiosity)

Last updated at June 1, 2026 by

Q 9
Question

Yadu conducted an experiment to test his idea. He took two test tubes, A and B, and added a pinch of rice flour to the test tubes, half-filled with water and stirred them properly. To test tube B, he added a few drops of saliva. He left the two test tubes for 35–45 min. After that, he added iodine solution into both the test tubes. Experimental results are as shown in Fig. 9.15.

What do you think he wants to test?

🔗 Concept: 9.1.1 Stop 1 — The Mouth

Question 9 — Yadu conducted an e - Life Processes in Anim - [Teachoo] - Questions at the end of the chapter
Fig. 9.15: Experimental results showing test tube A blue-black, test tube B clear
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Yadu wants to test whether saliva can break down starch in rice flour into simpler sugars.

Explanation

  • Test tube A (rice flour + water, no saliva): iodine turned blue-black — starch is present.
  • Test tube B (rice flour + water + saliva): iodine showed no colour change — starch is no longer present.
  • This shows that saliva broke down the starch in rice flour into simpler sugars over 35–45 minutes.
  • The experiment demonstrates that saliva contains a digestive juice that breaks down starch — which is why starchy food tastes sweet when chewed for a long time.
Yadu is testing the digestive action of saliva on starch. The results confirm that saliva breaks starch into sugar.
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