Anonymous Student #2
The purpose of this lab was to use the scientific method to identify an unknown solution, based on the reactions (i.e. color changes) of known solutions with indicator solutions. These known solutions contained different types of macromolecules. Each type of micromolecule reacted with at least one indicator solution in a unique way, which allowed us to identify the macromolecule based upon the presence or absence of a color change. Water was also used as a control solution, as it showed a negative reaction with the indicator solutions.
Seven sets of three 10ml test tubes were set up, with one set for each of the following sample solutions: water, protein, starch, lipid, vitamin C and an unknown sample. 0.5 L of each solution was added to each tube. One drop of each of the three indicator solutions (iodine, Sudan III and Biuret & copper sulfate) was added to each sample solution to determine how that sample solution (and that type of macromolecule) would react with each specific indicator. The results were recorded in the data chart below. The identity of the unknown solution was determined by comparing the reactions of the unknown solution with the reactions of the five known solutions as presented in the Discussion section below.
This experiment produced results which provided a clear understanding of the color change that occurred when each known solution reacted with each indicator solution. When the color changes associated with the Unknown solution were compared with those of the known solutions, the identity of this unknown was determined to be starch.
Method and Materials