Question

7. The image shows an experiment set up in which boiled rice was taken in test tube A and boiled and chewed rice was taken in test tube B. When iodine solution is dropped into both the test tubes, the colour of water in test tube A changed to blue black, but the colour in test tube B remained unchanged.Give reason.​

Answer 1

Answer:

Due to presence of starch

Explanation:

Rice contains starch in it which is complex sugar and it is very difficult to digest !

So to overcome it our body releases saliva(contains salivary emylase in it )

Now when we chewed rice saliva get mix with starch and convert it to simple sugar (which is not starch).

Iodine only reacts with starch to give purple colour but here all. starch gets converted so in test tube iodine does not show any reaction!

(if you are in 7th or 8th grade then simply understand that

in test tube A starch is present but in test tube B starch is not present because our saliva converts it)

ok i think it may helps you !

Answer 2

Test tube A shows the change in color on the addition of iodine solution because of the presence of starch in the boiled rice.

Explanation

IODINE TEST -

• The chemical reaction to experiment with the presence or absence of starch in the solution.
• The starch-iodine combination shows deep blue-black color in the reaction.
• In test-tube A, the boiled rice contains starch content.
• When iodine is added in test tube A, starch in the rice reacts with the iodine solution and shows a change in color.
• The color changes from white to deep blue-black of the starch-containing rice.
• In test-tube B, the boiled rice is chewed first and then used for the experiment.
• The starch has been acted upon the digestive enzyme of saliva.
• Salivary amylase in saliva digest starch into a simple form.
• Iodine does not react with the digested starch and fails to show the change in color of the solution.