Good and Bad Lipids
Middle School (grades 6 -8)
Difficulty of Project
Iodine is irritating to eyes, respiratory system and skin and stains hands and clothes. Iodine is toxic, harmful if inhaled or swallowed and the vapors may cause drowsiness and dizziness. The investigator should wear goggles, work in a well ventilated area, and follow safety precautions when using iodine.
The materials required for this project are readily available and inexpensive.
Approximate Time Required to Complete the Project
1 to 2 hours to complete the activity once the materials are secured and setup. Also between 1 and 2 hours to prepare the Tri-fold board display.
This project focuses on saturated and unsaturated lipids (fats and oils). Diets high in saturated fat are linked to high blood cholesterol levels and heart decease. High-fat diets can also increase the risk for obesity and cancer. The research aspect of this science fair project is to use a simple iodine test to determine if several common lipid products are saturated or unsaturated.
The young investigator will test if a lipid is saturated or unsaturated by adding iodine to various substances. If the iodine changes from brown to clear the lipid is unsaturated. If the iodine does not change colors the lipid is saturated. From the observations made data tables will be generated and the results displayed in the form of a graph.
The practical application from the results of this project is to reinforce the idea that as part of a healthy diet we should try to reduce the amount of saturated lipids and trans-fats we eat and replace them with unsaturated lipids.
Materials and Equipment / Ingredients
Eight test tubes, small graduate cylinder, Tincture of iodine, vegetable oil, distilled water, butter, margarine, fish oil, olive oil, corn oil, and sunflower oil.
The oils, butter, margarine, and distilled water can be purchased from the local supermarket. Tincture of iodine is available from any drug store or the pharmacy department of most major retail (Wal-Mart, Target, etc) stores. Test tubes and a small graduate cylinder may be borrowed from a high school or college chemistry teacher, found in toy chemistry sets, or purchased from a hobby shop.
Fats, oils and waxes belong to a group of compounds called lipids. Fats and oils have the same chemical structure. Fats that are liquid at room temperature are called oils. Fats and oils are insoluble (do not dissolve) in water. The cell membrane is made up of lipids and proteins.
Fats and oils are made-up of two kinds of molecules, glycerol and fatty acids. Three fatty acids are bonded to one glycerol to form a lipid called a triglyceride.
Each fatty acid is made of a chain of carbon atoms with hydrogen atoms attached. There are two kinds of fatty acid: saturated and unsaturated. Bonds between carbons may be single (C-C) or double (C=C). The presence of double bonds implies that the carbon chain of a lipid is not saturated with hydrogen atoms. That is, less than the maximum number of hydrogen atoms possible is bound to the carbon. The following diagrams illustrate saturated and unsaturated fatty acid lipids.
To test if a lipid is saturated or unsaturated iodine is added. If the iodine changes from brown to clear the lipid is unsaturated. If the iodine does not change colors the lipid is saturated.
Iodine + Lipid = brown color (saturated)
To test for the degree of lipid saturation iodine is added to the unsaturated lipid. The iodine will attach itself to one of the double bonds which causes de-colorization of the iodine. As shown in the illustration below.
Digital photos can be taken during the experimenting process and the following websites offer down loadable images that can be used on the display board: