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Science · 2024 · 2 marks
CBSE 2024 · Region 2 · Set 2 · Q22
Two test tubes A and B are taken, each containing one mL of starch solution. Add 1 mL of saliva to test tube 'A' only and leave both the test tubes…
Two test tubes A and B are taken, each containing one mL of starch solution. Add $\displaystyle 1$ mL of saliva to test tube 'A' only and leave both the test tubes undisturbed for a few minutes. Now add a few drops of dilute iodine solution to both the test tubes.
(a)
Which one of the two test tubes shows change in colour ? Write the changed colour observed in this test tube.
(b)
What can we conclude from this activity ?
Marking-scheme solution
(a)
Test Tube B
Blue-black
(b)
Starch is digested by saliva in test tube A, so no change in colour . Alternate answer
Saliva contains enzyme which converts starch solution to sugar, so no change in colour.
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CBSE Class 10 Science past-paper question from the 2024 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.