Introduction and Hypothesis: In this experiment, we used iodine to test for starch in certain solutions. Iodine separates starch from polysaccharides, monosaccharides, and disaccharides. Starch is a curled polymer of glucose and iodine interacts with molecules, which changes the color of the molecules to a kind of black color. Iodine does not respond with carbohydrates that are not curled or coiled, thus the color stays yellowish brown. A black color result means that starch is current and a yellowish brown color result means that starch is not current. In the test for starch, we will be adding 3 drops of iodine to 7 different solutions to see if there is any presence of starch. My hypothesis is if a solution is present with starch then it will respond with iodine solution and change to a black color.
Materials and Methods: First, we got 7 test tubes and labeled them 1-7. Then, we added 5ml of a different solution to each test tube. After that, we added 3 drops of iodine to each solution. Finally, we jotted down the results and colors of each tube. The experimental group is 5mL of each of these solutions: onion juice, potato juice, sucrose, glucose, distilled water, reducing sugar, and starch. There is no control group because all the solutions are being experimented on. Iodine is the independent variable because you control how many drops of iodine are put in each solution, while the dependent variable is all the solutions that are being tested. In the experiment, we wanted to see the qualitative characteristics that the results had. We were looking to see what colors change each solution had by adding the iodine. If the solution had changed to a black or a bluish black color, then starch was present. We didn’t replicate the experiment because we got the data that we were looking for.
Results: From the many solutions that were tested, it was believed that out of the solutions the starch and potato juice solutions had a positive
References: Vodopich, Darrell, and Randy Moore. Biology Laboratory Manual. 9th ed. McGraw Hill, 2011. 59-60. Print.