Grease Spot Test Solution Tested % glucose 0.5% starch 0.5% albumin Translucent Spot? Fat Present? mineral oil water unknown 1) Did you expect these results? 2) Why or why not? 3) Did any other substance than oil result in a translucent spot? 4) Why? PROCEDURE #5: Emulsion Formation Emulsion Formation (+/-) Tube 1 5 ml water + detergent 1-2 drops Sudan III 2 drops mineral oil Tube 2 5 ml water + large scoop bile salts 1-2 drops Sudan +2 drops mineral oil
The Correct Answer and Explanation is:
Grease Spot Test Results
- Did you expect these results?
Yes, I would expect these results, but the exact outcome can depend on the properties of the tested substances. The grease spot test is used to detect the presence of fats, oils, or lipids by observing the appearance of a translucent spot on the test paper. Mineral oil should definitely produce a translucent spot due to its lipid nature, while water, starch, and albumin should not produce the same effect, as they are not lipid-based. - Why or why not?
The grease spot test works by detecting substances that are hydrophobic (non-polar) and can leave a translucent mark on the paper. Substances like mineral oil (which is a fat) should result in a translucent spot. Water, starch, and albumin, on the other hand, are polar molecules that do not have the same property of causing translucency on the paper. Water will absorb and evaporate without leaving any visible trace, starch would likely not leave any mark unless it is specifically in its lipid-like form, and albumin is a protein, which is also polar. - Did any other substance than oil result in a translucent spot?
Based on the information provided, no other substance other than the mineral oil is expected to cause a translucent spot. Water and starch are hydrophilic, meaning they do not interact with the paper in the same way that hydrophobic substances do. Albumin may form an opaque mark, but it would not leave a translucent spot typical of fats or oils. - Why?
The reason mineral oil creates a translucent spot while other substances do not is due to the fact that mineral oil is composed of long hydrocarbon chains that are non-polar. These hydrocarbon chains interact with the cellulose fibers of the paper, creating a transparent or translucent spot. The polar substances (like water, starch, and albumin) do not have this property. Water, for instance, is polar and does not interact with the paper in a way that would result in translucency.
Emulsion Formation Results
- Tube 1: Water + detergent + Sudan III + mineral oil
Expected Result: A positive emulsion would form due to the detergent’s role in emulsifying the oil and water mixture, resulting in a homogeneous solution where oil droplets are dispersed in water, leading to a slight color change from the Sudan III dye. - Tube 2: Water + bile salts + Sudan III + mineral oil
Expected Result: Bile salts, being amphipathic (having both hydrophilic and hydrophobic regions), would act similarly to detergent by emulsifying the mineral oil. This would create a more stable emulsion than in Tube 1, as bile salts naturally help to emulsify fats and oils in the digestive system.
In both tubes, the emulsion formation is indicated by the dispersion of oil droplets in water, which can be visualized by the Sudan III dye staining the oil phase. The difference between the two tubes lies in the nature of the emulsifying agents (detergent vs. bile salts), which affect the stability and efficiency of the emulsion.
The success of the emulsion formation is a result of the detergent or bile salts reducing the surface tension between the oil and water phases, allowing them to mix and form an emulsion.
