Experiment 1: Modeling Basic Organic Compounds
In this experiment you will make molecular models of various hydrocarbons and then test unknowns for the presence of either carbohydrates or lipids.
54 Raisins24 Marshmallows
For each of the structures listed in Table 3, draw the structure named, count the number of carbon atoms and hydrogen atoms, count the number of C-H bonds, count the number of C-C, and count the number of bonds.
Construct models of each of the organic compounds using the raisins (hydrogen atoms), marshmallows (carbon atoms), and the toothpicks (each represents a single bond) in your lab kit. Refer to Table 3 for specific molecules to construct. The first example, propane, is drawn below.
Table 3: Carbon Molecule Data
# H Atoms
# C Atoms
# C-H Single Bonds
# C-C Single Bonds
# Double Bonds
# C≡C Triple Bonds
Which organic compounds contained double bonds? Triple bonds?
Draw an organic molecule that was not included in Table 3 that contains a double bond. Name the compound.
Experiment 2: Testing for Carbohydrates
In the following experiment, you will test for the presence of different organic compounds. You will use water as a negative control. A negative control will result in no change in color. For example, if you are testing for the presence of carbohydrates, the test chemical, IKI solution, will remain the original color when mixed with water.
1 pinch of Unknown A10 Drops of Unknown B10 Drops of Unknown C1 pinch of Unknown D3 - 4 drops IKI Solution5 Test tubesTest tube rack
3 PipettesPermanent marker10 mL Graduated cylinder*Distilled Water
*You must provide
Place five test tubes in the test tube rack.
Use a permanent marker to label each test tube as Unknown A, B, C, and D. Label the fifth test tube "water".
Place one pinch of powdered Unknowns A and D into their respectively labeled tubes. Then, add 10 mL of water into test tubes A and D.
Use a pipette to place about 10 drops of unknowns B and C into their respectively labeled tubes.
Place 10 drops of water in the "water" test tube.
Add three to four drops IKI solution to each test tube and observe any color change. If a carbohydrate (starch) is present in the unknown, the solution will turn a purple-black color upon addition of the IKI solution.
Record your observations in Table 4. A positive result (visible color change) indicates that starch was present. A negative result (no color change) indicates that there was no starch.
Table 4: Starch Presence Results
Which unknown(s) contained a carbohydrate? How do you know?