Question

Prachi performed an experiment as shown below.
figure

Study the two figures carefully. On adding iodine, only the mixture in test tube A changed to blue black whereas the mixture in test tube B remained the same colour. Can you say why?

Answer 1

Test tube A has only boiled rice, which has starch. Hence, it gives a blue-black colour on reaction with iodine. Test tube B has chewed rice mixed with saliva. The enzyme present in saliva digests the starch into sugars. Hence, the colour of the mixture does not change on adding iodine.