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Organic Compounds Lab Report

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Autor:  radonda_84  21 May 2010
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Identifying Organic Compounds
Joe Harris 11/12/07
1. Background
Organic compounds are, by definition, any chemical compound containing carbon. These compounds include carbohydrates, polysaccharides, lipids, proteins, and nucleic acids. Each one of these compounds has a different purpose. Carbohydrates give energy to cells when consumed. Lipids are basically the fats of a cell. Proteins are the building blocks of muscle in a cell. Nucleic acids are used to transfer genetic information from one cell to the other.
The purpose of this lab is to simply determine the absence or presence of the main chemical content of a given substance. In previous labs, there were tests with three chemicals, Lugol's solution, Benedict's solution, and Biuret solution. The tests were qualitative and tested for the presence of sugars, starches, or proteins within a given substance. The substances were already known, so the tests were used to figure out what each solution showed presence of. After going through all of the tests, Lugol's solution showed the presence of starch, Benedict's solution showed presence of sugar, and Biuret solution showed presence of protein. In this lab, these solutions will be put to the test.
2. Materials and Methods
A. Materials
The following materials are needed to complete this lab:
Benedict's solution
Lugol's solution
Biuret Solution
unknown substance A
unknown substance B
2 pipettes (one for each substance to avoid contamination)
hot plate
beaker
2 test tubes
labels
notebook
pen/pencil
test tube tray/holder
drying rack
B. Procedure
1.Take one label per test tube and label one test tube “A” and one “B”.
2.Fill test tube A with 3 pipettes full of substance A.
3.Fill test tube B with 3 pipettes full of substance B.
4.Take the Benedict's solution and apply 10 drops of it into each test tube.
5.Swirl to mix.
6.Prepare water bath, take the beaker, fill half with water, and heat to between 40 and 50 degrees C.
7.When water bath is ready, put each test tube into the water bath. Wait 5 minutes.
8.After 5 minutes, remove test tubes from the water bath set in test tube holder and record results. Also turn off hot plate.
9.Clean both test tubes thoroughly.
10. Repeat steps 2 and 3.
11.Add 10 drops of Lugol's solution to each test tube.
12.Swirl to mix.
13.Record data.
14.Clean both test tubes thoroughly.
15.Repeat steps 2 and 3.
16.Add 10 drops of Biuret solution to each test tube.
17.Swirl to mix.
18.Wait 1-2 minutes.
19.Record data.
3. Data and Results
A. Data Tables
Benedict's Test
Test Tube
Original Color
Final Color
Tube Contains
+ or -
A
Light Blue
Orange
Sugar
+
B
Light Blue
Light Blue
Still Unknown
-

Lugol's Test
Test Tube
Original Color
Final Color
Tube Contains
+ or -
A
Clear
Yellow
Still Unknown
-
B
Clear
Dark Purple
Starch
+

Biuret Test
Test Tube
Original Color
Final Color
Tube Contains
+ or -
A
Clear
Light Purple
Protein
+
B
Clear
Clear
Clear
-

4. Conclusion
During the Benedict's test, the contents of tube B did not change, indicating the absence of sugar in that particular substance. However, the contents of tube A did change orange indicating the presence of sugar in that substance. During the Lugol's test, the content of tube A did not change dark purple indicating the absence of starch in that substance However, the content of tube B changed to dark purple indicating the presence of starch. During the Biuret test, test tube B did not change indicating the absence of protein in that substance. However, test tube A changed light purple indicating the presence of protein in that substance. These tests are all qualitative tests, therefore testing only for presence or absence of a sugar, starch, or protein. With that said, food industries could use these tests for their own use. They could take a food unknown to them and do the Benedict's test procedure. If the color of that substance turned orange, there would be sugar in that substance. They could then follow-up with using a quantitative test that shows how much sugar is in that particular substance.

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