Comparative Effectiveness of Various Surfactants: Experiment

Topic: Experiment Words: 653 Pages: 2

Table of Contents

Introduction
Methods
Results
Discussion
Conclusion

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

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.
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.
A small quantity of each surfactant was added to each of the test tubes (in step 1) after which the test tubes were shaken.
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.

Surfactants	Water (A)	Hard Water (B)	Sea Water (C)	Acid Water (D)
Commercial shampoo	A small amount remained white and sudsy when shaken	Less foamy than the previous white/ cloudy solution	Cloudy, very little suds. Similar to previous	More soapy with extra white or cloudy suds
Synthesized shampoo	Lightly changed to pink and became soapy with a cap of bubbles	Turned light pink with separation and coagulation of white film	Remained clearer than the previous mixture	Cloudy white
Bar soap	The mixture had blobs that initially separated, but later clumped together	Egg-yolk appearance stayed completely separated	White blob-like, coagulated	The mixture remained as a film on top
Liquid dishwashing soap	Slight yellow tint, more suds	Cloudy, mixed with a slight yellow tint	Cloudy and foamy with a slight gray tint	Breaking up clumps, some mixed completely after shaking then separated into strands after some time
Rinse aid	Clear with a few clear bubbles on top	Film suspended with a light blue tint	Initially separated then turned cloudy with granules in it	The mixture initially seemed to stay at the bottom. It then turned light blue and mixed.

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.