![]() ![]() This is what separation looks like, a process you’ll need to be familiar with to collect data in the next step. Take a moment to observe the two layers of oil and vinegar as they avoid mixing with one another. Using a clean pipet, add 8 mL of oil to each test tube.Using a pipet, add 8 mL of vinegar to each test tube and swirl to fully mix in the emulsifier.Label each test tube with the emulsifier that was added, and label the empty one “control.” Label the data sheet with the emulsifiers you will test. To each of three test tubes, add 2 g of an emulsifier to be tested, putting a different emulsifier in each test tube.Use a scale to measure 2 g of each of the emulsifiers you will test.Set out four clean 20-mL test tubes in a test tube rack. ![]() Because oils also repel water, they are called hydrophobic, which means “water-fearing.” Oils repel polar molecules such as those found in vinegar. You can observe this phenomenon by placing a few drops of oil on the surface of a bowl of water-eventually the drops will form a single large oil slick. Most of the atoms in a fatty acid molecule share electrons evenly and are neither negatively nor positively charged (although fatty acids do contain small regions of polarity-just not enough to make the whole molecule polar.) Nonpolar molecules love other nonpolar molecules and will glom together when mixed with water. Fats and oils are composed primarily of long molecules called fatty acids (usually bound together by glycerol molecules into groups of three called triglycerides). Oils are a type of fat (like butter, shortening, and lard) and are considered nonpolar. Polar molecules are attracted to water molecules-which are also polar-and are called hydrophilic, which means “water loving.” Polar molecules are generally attracted to other polar molecules because their slightly negative poles have an affinity for their slightly positive poles. These slightly charged poles arise because one or more atoms in the molecule are electronegative, meaning that they tug electrons-which are negatively charged-towards them, creating an uneven distribution of charge within the molecule. Water, acetic acid, and alcohol are all examples of polar molecules-molecules that have a slightly negative charge at one end, or pole, and a slightly positive charge at another end. Most vinegars are solutions of acetic acid and water (plus some other acids and alcohols, depending on the type of vinegar you are using).
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