While using iodine in the laboratory, some drops of iodine fell on Paheli's socks and some fell on her teacher's saree. The drops of iodine on the saree turned blue-black while their colour did not change on the socks. What can be the possible reason?

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Solution

Iodine test:
Iodine is used to test the presence of starch in a particular sample.
If the sample contains starch, it will produce blue-black color depicting the positive result.
Given condition:
The teacher's saree showed positive results for the presence of starch because starch is used for polishing the sarees.
This is why the starch remaining in the saree is responsible for creating the blue-black color as it is spilled.
Paheli's socks clearly lack the starch and that is why no color change is observed as drops of iodine fall on it.

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