Hobbies And Interests
Vitamin C Solution
Pour 500 milliliters of water into a glass jar and then crush a 500 milligram vitamin C tablet and add it to the water. Stir the mixture until the vitamin C is dissolved. The solution is now 1 milligram of vitamin C for every 1 milliliter of water. Pour 20 milliliters of this solution into a glass and pour in half a glass of water.
Adding Starch
Add 2 tablespoons of cold water into a glass. Drop in a teaspoon of flour and stir. Pour this glass into a half glass of boiling water and stir until the starch is completely disolved. Allow this to cool and you have a starch solution. Transfer 1 teaspoon of this to the vitamin C solution. You now have a vitamin C and starch solution.
Iodine Drops
Fill an eye dropper with iodine solution and squeeze a drop at a time into the vitamin C and starch solution. Ensure that you stir with your freehand as the drops are being added. It is also vital that you count every drop. At some point the mixture will turn dark blue; write down the number of drops you added when this happens.
Samples
Gather a variety of juices that contain vitamin C to test in the same way you did with the vitamin C solution. These could be orange juice, cranberry juice, grapefruit juice or tomato juice. Estimate before conducting the tests how much vitamin C will be in each juice.
The Test
Add 20 milliliters from one of your samples into a glass. Pour in half a glass of water and some of the starch solution just like you did with the solution you made earlier. Perform the iodine eye dropper test on the sample and record how many drops it took to turn the water blue. Make sure to use the same starch solution, iodine solution and eye dropper so there are no variations. Divide the number of drops it took to turn your sample dark blue by the amount it took to turn the original solution dark blue. This is the number of milligrams per milliliter of vitamin C in the sample. So if orange juice took 12 drops and the solution took 44, it would mean that there are 0.272 milligrams of vitamin C per milliliter in the juice. See how close your estimates were to the actual amount of vitamin C in each juice.
Explanation
It's now time to explain the science behind your project. Iodine is an oxidizing agent and Vitamin C is an ascorbic acid. Ascorbic acid's give away electrons and oxidizing agents take them. Once iodine takes in electrons it becomes iodide. The difference between these two agents that matters in this experiment is the iodine changes the color of starch and iodide does not. So as long as there is vitamin C in the glass the starch will not change color. Once the color does change though you know that the vitamin C, because the iodine is not being changed.