Identifying the unknown
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Biology (block 4) Today, my peers and I, will be allotted a certain amount of time to conduct a series of tests to attempt to identify a variety of unidentified house hold substances.
The following items are required materials: * Brown paper * Biuret Solution * Lugol's Solution (Or Iodine) * Benedict's solution * Hot plate * Large Beaker
We were attempting to identify the following substances: * Heavy Cream * Corn Oil * Water * Fat Free Milk * White Grape Juice * Gatorade
These are the tests that were taken as procedural measures: * Sugar test * Lipid test * Protein test * Starch test
When it comes to the sugar test we had to take the following steps: * Fill beaker half way with water and place on hot plate. * Obtain 5 ml of sugar solution and place it in one test tube. * Fill the other test tube with an equivalent amount of water. * Place 4 drops of Benedict's solution in each test tube. * Look at the color of the solution in each test tube. * Place the test tubes containing the liquids into the hot water. * Observe for any color changes in the solutions.
Now with the starch test we had to take very different steps to reach our conclusion: * Take 5 ml of starch solution and place in one test tube. * Fill the other test tube with an equivalent amount of water. * Put 2 drops of Lugol's solution in each test tube. * Look for any color changes in the solutions.
The next step is the lipid test you will notice how simplistic it seems, but has the longest duration: * Place one or two drops of solution to be tested on a piece of brown paper towel. * Allow towel to dry. * Observe appearance of towel.
When conducting the protein test you will notice extensive similarities to the starch test: * Take approximately 5 ml of protein solution and put it in one test tube. * Now you’re required to fill the other test tube with an equivalent amount of water. * Put 2 drops of Biuret solution in each tube. * Watch for any changes in color in the solutions.
The results:
Protein test: No change in any of the substances.
Starch test: Only “D” reacted positively. The rest were non-reactive (Negative)
Sugar test: Only “A” was determined as reactive (Positive). The other substances were deemed negative for sugar contents.
Fat test: “A”,”B”,”D”, and “G” became transparent. (“D” was oily) (“B” was dark and rough) (“A” and “G” were still somewhat solid) Reasoning:
My group and I participated in every test and activity so we are positive of the contents of each substance. We also used our common sense like the fact that only one out of the seven liquids were thick, so we determined that it was heavy cream. We also wafted and noticed that the corn oil had a significant smell that automatically made us aware of its “identity”. There were multiple procedures taken outside of the predetermined 4 tests. When the class had completed all of the tests we wrote our results on a work sheet and came to the conclusion that we were all accurate with our indication of identification.

Conclusion: When we approached our conclusion we were baffled by how many of our pre-test guesses were correct. We created several hypotheses based on a few of our human senses such as sight and smell. As I stated before most were correct but some weren’t and that is when the 4 tests came in handy. In conclusion I learned how using the lipid, starch, sugar, and protein tests can help determine what nutritional components a substance contains.