Table of Contents Chapter 10: Soap Sense |
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Chapter ChallengeIn this chapter, you are challenged to create a soap from natural sources that are readily available. In working through the activities, you explore variations in the two main ingredients of soap and their effect on the properties of your target soap. At the conclusion, you will prepare two presentations—one for corporate executives of a soap company and a second for the marketing department of that company. |
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Activity Summaries |
Chemistry Principles |
Activity 1: What Makes a Good Soap? Students list different cleaners and soaps and describe their characteristics. They design and administer a survey to identify the most important characteristics. They choose a characteristic they want to measure quantitatively, and design an experiment to do so. After running the experiment,they discuss possible revisions. |
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Activity 2: Modeling Molecules Students build organic molecules of steadily increasing complexity, and examine the chemical bonding rules which determine these structures. A fat molecule is modeled and subjected to saponification and a skit is performed to demonstrate this reaction.
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Activity 3: How Do You Clean Dirty Laundry? Students test different cleaning solutions of varying polarity on different types of “dirt” to see which ones are most effective. They will discover that most types of dirt fall into one of two categories (polar or non-polar) and that laundry detergent in water will wash out most of them. Students perform a couple of quick experiments involving static electricity, observing that water behaves like a charged object and kerosene does not. |
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Activity 4: How Does Soap Work? Students explore surface tension and the effect of soap on it. They then separate various liquid sand solids according to their polarity. Models to describe the behavior of interactions between polar and non-polar substances are designed. The effect of adding a surfactant is considered, and students will also observe the characteristics of a mixture of water and oil. |
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Activity 5: How Does Chain Length Affect the Properties? Students determine the melting points of three saturated fatty acids of increasing chain length,identifying the trend. They examine a heating curve to help understand the phase transition between the solid and liquid states, and generate an explanation for this behavior. They examine three soaps made with high percentages of these three fatty acids, looking for trends between the properties and increasing chain length. |
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Activity 6: Changing the Fat: Does Unsaturation Make a Difference? Students use paper clips to model the overall shapes of a related series of fatty acids with increasing numbers of double bonds and examine the relationship between shape and melting point. They model the packing behavior of each acid, then predict and measure their melting points. Students will examine the properties of soaps containing large amounts of these fatty acids in terms of the number of double bonds. They will then predict the attributes of other soaps with these fatty acids. |
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Activity 7: Soap, Other Bases, and pH Students measure the pH of an array of different soaps brought from home, and use acid to neutralize the pH of the soap. Then they measure the pH of an acid solution and try to dilute the acid enough to change the pH by 1 unit. After they discover the amount of water required to change the pH by 1 unit, they make predictions for more pH changes and carry them out. |
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Activity 8: Making Soap Functional and Appealing Students test and compare the soap they bought as a target to the soaps they made before beginning the chapter. They consider the properties of the various fats available and choose one or more as the basis for the soap they will design. After learning about moisturizers, thickeners, pH adjustments, and foaming agents, they decide whether to include any of them or not. Finally, they make the soap they have designed. |
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