when you're doing an experiment on enzymes when you add acid+saliva+starch+iodine why does the colour change to blue black​

I do any

Explanation:

najsjva.w.wnwjw..

Because if there is a minimal variation of it the normal state of pH, it can cause severe effects in the brain, arteries, the heart, and other organs. 
In other words, it can have some serious effects on the body systems that can lead big diseases, like cancer.