Lab #8

A. Introduction

In this lab we made soap through base hydrolysis (saponification) and test its properties against commercial soap and detergent. Soap is the sodium salt of a fatty acid that is used to remove dirt and oils. When fats or oils react with a strong base like sodium hydroxide then the bonds break down to produce soap and glycerol. Soap molecules have a dual nature: a polar head that mixes with water and a nonpolar tail that mixes with oil. This allows soap to trap grease in clusters called micelles so they can be washed away. In this lab, we tested sudsing, pH, behavior in hard water, solubility, lipid traits, and reactions with acid.

B. Materials and Methods

  • Part I: Saponification: Heated a fat/oil sample with a strong base to create and isolate solid soap.

  • Part II: Soap Testing: Dissolved the synthesized soap, commercial soap, and commercial detergent in water, shook them to observe sudsing, and checked their pH with indicator strips.

  • Part III: Hard Water: Added a hard water solution to all three soap/detergent samples to observe color and texture changes.

Part IV: Solubility: Observed vegetable oil and cottonseed oil mixed with water before and after adding sodium carbonate

  • Part V: Lipid Test: Dropped vegetable oil, cottonseed oil, and distilled water onto paper to see how they spread and if they left a grease spot.

  • Part VI: Reaction with Mineral Acids: Added hydrochloric acid to the synthesized soap and detergent to look for visible changes or precipitates.

C. Results

Table 1. Data for the Saponification of a Triacylglycerol

  • What is soap? Soap is the sodium salt of a fatty acid that is used to remove dirt and oils.

Table 2. Data for the Soap Testing (Suds and pH)

  • Our Synthesized Soap: Observations: Barely any suds. pH: 12

  • Commercial Soap: Observations: barely any. pH: 6

  • Commercial Detergent: Observations: barely any. pH: 10

Table 3. Data for the Hard Water Testing

  • Our Synthesized Soap: Soap became white compared to its previous harsh orange color.

  • Commercial Soap: Turned into a more foggy color/appearance.

  • Commercial Detergent: Turned into a lighter color.

Table 4. Data for the Solubility Test

  • Vegetable Oil: Before: sudsy and separated. After: foggy and also separated but turned a different shade color.

  • Cottonseed Oil: Before: not sudsy but it clearly separated. After: no noticeable difference.

Table 5. Data for the Lipid Test

  • Vegetable Oil: Slow spreading, stayed in one spot, left a greasy spot.

  • Cottonseed Oil: Slow spreading, stayed in one spot, left a greasy spot.

  • Distilled Water (H2O):The paper absorbed easier & it spread faster. It didn't leave a greasy spot.

  • Comparison: Vegetable oil and cottonseed oil are similar because they both leave a greasy, translucent spot on the paper. Distilled water may look wet at first, but it evaporates and leaves no spot.

D. Discussion

This lab showed how soaps and detergents behave differently based on their chemical traits. None of the samples made many suds, likely because they were too diluted or our homemade soap was not fully finished. The pH test showed that our synthesized soap was very basic with a pH of 12, which means it still had leftover sodium hydroxide base in it, while commercial soap was a mild pH of 6 and detergent was a pH of 10. In hard water, our soap turned white and the commercial soap turned foggy because real soap reacts with hard water minerals to create an insoluble solid called soap scum. The detergent just turned lighter because detergents are chemically designed to not create scum in hard water. When we added hydrochloric acid, our soap turned back into a solid fatty acid precipitate, but the detergent showed no visible reaction because detergents can stay completely dissolved in acid. Finally, the lipid test proved that vegetable oil and cottonseed oil are thick fats that do not evaporate, so they leave permanent grease spots on paper, unlike water which dries up completely. Our main errors were not heating the soap long enough and not washing out all the leftover base during filtration.

E. Conclusion

In conclusion, soap was successfully created through the base-catalyzed hydrolysis of a triacylglycerol lipid. The experimental results demonstrates that synthetic detergents possess a superior chemical structure to traditional soaps for heavy-duty cleaning, as they remain fully functional and soluble without forming precipitates when exposed to hard water or strong mineral acids.