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Introduction
Surfactants refer to chemical substances that lessen the surface tension in water. Lowering the surface tension of water makes it possible for dirt to dissolve in it. Therefore, washing is made easier by the inclusion of surfactants in the washing water. Surfactants can be categorized into four main groups namely ionic, non-ionic, amphoteric, and cationic surfactants. Cationic surfactants possess a positive charge on their polar portions, whereas anionic surfactants have a negative charge on their polar sections. Amphoteric surfactants contain negative and positive charges on their polar regions. Nonionic surfactants, in contrast, possess no charge on their polar portions.
Soap is an example of an anionic surfactant obtained from the reaction between oils or fats and strong aqueous alkalis. Such reactions are usually referred to as saponification reactions. This experiment aimed at establishing the comparative effectiveness of various surfactants. It also aimed at preparing a shampoo. It was expected that hard water and seawater would not easily form lather with detergents.
Methods
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Approximately 2 ml of distilled water, hard water, seawater, and acidic water were put in four different test tubes that were labeled A, B, C, and D.
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An anionic surfactant (shampoo) was made by putting 2 ml of 5% triethanolamine in a test tube. The solution turned pink when one drop of phenolphthalein indicator was added. 5% oleic acid in ethanol was added dropwise to the test tube until the pink solution turned colorless.
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A small quantity of each surfactant was added to each of the test tubes (in step 1) after which the test tubes were shaken.
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The changes in the test tubes were observed and recorded.
Results
It was observed that the hot pink solution in step 2 above lightened in color when oleic acid was added. As more acid was added, the mixture became sudsy and shampoo-like.
Discussion
Saponification occurred when all the oil in oleic acid reacted with triethanolamine. Phenolphthalein indicator displayed a pink color in triethanolamine, which was a base. The color change from pink to colorless indicated that the saponification reaction was complete since all the alkali had reacted with the oil.
It was realized that bar soap was the only surfactant that did not form lather with all the water samples. Conversely, the commercial shampoo lathered with the different water types. However, little bubbles were seen when commercial shampoo was mixed with hard water and seawater. That was because seawater and hard water contained dissolved salts and minerals that made the formation of lather difficult. Dishwashing liquid and homemade shampoo displayed a moderate ability to form lather with all four types of water.
Conclusion
It was concluded that commercial shampoo was the strongest surfactant, whereas bar soap was the weakest surfactant. It was also concluded that seawater and hard water did not lather easily with detergents.
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