The indicator test used to test for the presence of starch in an unknown substance is known as the iodine test or iodine solution test. Here's how it works:
Iodine Test for Starch:
Materials Needed:
Iodine solution (commonly known as iodine tincture)
Unknown substance (e.g., food sample)
Procedure:
Take a small amount of the unknown substance and place it on a clean surface or in a small container.
Using a dropper or a pipette, add a few drops of iodine solution to the substance. Make sure the iodine solution is evenly distributed.
Observe the color change. If the substance contains starch, the color of the iodine solution will change from yellow-brown to a blue-black or dark purple color.
Explanation: Iodine solution contains iodine molecules that have an affinity for starch molecules. When iodine comes into contact with starch, it forms a complex known as "iodine-starch complex." This complex has a characteristic dark blue-black or dark purple color, which is easily noticeable.
If the substance being tested contains starch, the iodine solution will react with the starch molecules present, resulting in the color change. If the substance does not contain starch, the color of the iodine solution will remain the same (yellow-brown).
This test is a simple and effective way to detect the presence of starch in various materials, such as foods, plant samples, or other organic substances. It's commonly used in biology and chemistry labs to identify the presence of carbohydrates like starch.