Question

Few drops of dilute iodine solution is added to both the test tube.Blue colour appears in the test tube B.
What changes occur in test tube A? Why?​

Answer 1

Blue color appears due to the presence of starch.

Explanation:

• Iodine test is used to check the presence of starch.
• As we can see Test Tube A contains Saliva and Test Tube B contains crunched potatoes.
• Saliva contains starch breaking enzyme that is amylase while potato contains starch in it.
• Therefore when iodine is added in both tube the color of tube B changes to dark blue which indicates the presence of starch while no reaction takes place in tube A which means there is no starch.

Answer 2

Answer:

When will drop iodine solution on potato the area which comes under contact of iodine solution will turn blue-black due to presence of starch. If we put a drop of iodine on a cut potato, we can see that that the colour changes to blue-black. This indicates the presence of starch. ... we can say that it contains starch.