Scientists have established different ways to indicate presence of these compounds, one way is to test for these various compounds via solution tests. Scientists have established terms for evaluation. The terms include positive and negative control. Positive control contains the variable for which the test will react positively. A negative control on the other hand does not contain the variable and thus will result in a negative result. Solutions which contain the variable or compounds which react with the tests will produce a positive control; otherwise a negative control will result.
Materials and Methods An experiment was carried out to test the presence of certain organic compounds found in various solutions. The Benedicts test is to test for reducing sugars, Iodine test tests for starch, Beirut test tests for proteins, specifically peptide bonds between amino acids, lastly Sudan IV tests for lipids. Ten drops of various solutions including: onion juice, potato juice, sucrose solution, glucose solution, distilled water, reducing-sugar solution, and starch solution where each tested by Benedicts and Iodine tests respectively.
For the Benedicts test, each test tube containing the solution and ml of Benedicts solution were each placed in a hot water-bath for three minutes then examined for color change. The Iodine test was not however placed in the water-bath. For the Beirut test, illusions that were tested for include ml of each: egg albumin, honey, amino acid solution, distilled water, and protein solution. The Sudan IV test was carried out for the following ml solutions: oil with water, oil, honey, distilled water, and a known lipid solution.
Lastly an experiment for polarity was also conducted which consisted of oil mixed with distilled water and acetone respectively. As the reaction proceeded for each experiment color was recorded and that indicated either a positive or negative control for each solution. Results Each test results were recorded via color change. If color change occurred it indicated a positive control for the variable that was tested, if no color change occurred it indicated a negative control therefore the variable that was tested for was not present in the solution.
The results are as follows: Table 1 : Solutions and color reactions for Benedicts test and Iodine Test Tube Solution (10 drops of each) Benedicts Color change (ml) Iodine Color change (seven to ten drops) Onion Juice 2 Potato Jug ice 3 Sucrose solution 4 Glucose solution 5 Distilled water 6 Reducing Sugar solution 7 Starch solution In table 1, the following solutions tested positively for the Benedicts test: write which ones and their colors. Also the following solutions tested positively for the Iodine Test: write which ones and their colors.
Table 2: Solutions and Color reactions for the Beirut Test Tube Solution (2 ml of each) Color Albumen Honey Amino Acid solution Protein solution In table 2, the following solutions tested positively for the Beirut test: write which ones and their colors. Table 3: Solutions and Color reactions for the Sudan IV Test Tube Solution (Mil_ of each) Description of reaction Oil* water Oil+ Sudan IV Honey+ Sudan IV Distilled water+ Sudan IV Lipid Solution* Sudan IV
In table 3, the following reactions occurred to each solution: describe each reaction individually. Two test tubes, each containing 2 ml of oil and one contained distilled water, the other acetone. Each was observed as a mixture and it was clear that the water and oil did not mix which indicates no similar polarities between the two solutions. On the other hand the acetone and oil mixed relatively well which indicated similar polarities between the solutions.
Discussion It was clear that each solution containing the reducing sugar which includes the: list the solutions and colors, tested positively for the Benedicts test as expected. Each of the following solutions which contained starch: list them, tested positively for the Iodine test. Each solution containing lipids: list them, tested positively for the Sudan IV test. These results confirmed the expected hypothesis.
These tests are of benefit when testing unknown solutions, and as seen each test conducted showed a positive and negative control. With this information, scientists are able to identify solutions and compare results using a control. If something went wrong in your experiment this is where you would talk about it. State what went wrong and how it could be fixed. Conclusion Each test which was conducted in this lab confirmed the hypothesis and provided insight into how negative and positive controls are conducted in a laboratory setting.
The Benedicts solution which tested for reducing sugar contains copper ions, reducing sugars reduce these copper ions in nature to cuprous oxide, and thus color change occurred for the solutions that tested positively. The Iodine test contains iodine which interacts with the coiled polymer of the starch and thus produced as bluish black color to indicate such reaction. The Beirut test identifies peptide bonds between an amino acid chains protein), and thus produces a color change, it however does not interact with the amino acids themselves.
Lastly, the Sudan IV tests for lipids; this is based on the lipid’s ability to absorb pigment in fat dyes, such as Sudan IV. Polarities examine individual solutions based on their ability to mix and interact on a molecular level. The phrase, “like interacts with like,” is a good way to explain this phenomenon. Since the molecular composition of water and oils are not similar these reactions will not interact with each other unlike the molecular compositions of oil and acetone.