Understanding Soap When was soap first used Soaps
- Slides: 10
Understanding Soap
When was soap first used? Soaps have been excavated in clay cylinders that date back to 2800 B. C. An ancient Egyptian scroll dated to 1500 B. C. describes a soap recipe
People learned that fats would react with ingredients in fire ashes to produce soap + ASHES = FAT One common soap was made by mixing ashes with animal fat (also called tallow) https: //www. youtube. com/watch? v=t 0 Egt. Wv 6 k. BA SOAP
How is soap made today? Today, soaps are made from fats and oils that react with lye (sodium hydroxide) instead of ashes. Chemical Reaction: Fat or Oil + Na. OH Soap + Glycerol Because soap is made by this reaction, the reaction is sometimes called “saponification” https: //www. youtube. com/watch? v=Fuu 1 ZC g 5 byg
Back to Science 10… Recall that when you mix an acid and a base, a salt results: Acid + Base Salt This is actually how soap is made. Oils and fats (also called triglycerides) are acids Sodium hydroxide (lye) is written Na. OH and is a base Soap is a salt that results when the two react Interestingly, we use soap to cleanse grease and oils from our skin, but soap is made from grease & oils! This is a reminder that when a chemical reaction occurs, completely different substances are created!
How is soap made today? Saponification Reaction: Fat or Oil + Na. OH Soap + Glycerol Different fats or oils are used in the saponification reaction, and this produces soap with different qualities Examples of fats used to make soap:
How is soap made today? Tallow is beef fat that has been purified (“rendered”) https: //www. youtube. com/watch? v=DKOVo. As. IKh. Y Lard is rendered pork fat Solid fats like coconut oil, palm oil, tallow or lard form bars of soap that stay hard and resist dissolving in the water left in the soap dish.
The Structure of Soap • You start with a fat molecule, which contains: • H – hydrogen • C – carbon • O – oxygen • Fat molecules are also called “triglycerides”. You will notice three identical arms of the molecule, which is where the “tri” comes from • The various fats & oils that can be used in soapmaking all have this basic structure. A fat molecule (a. k. a. a triglyceride)
Build your own fat molecule… Then we’ll see what happens to it in the saponification reaction!
Saponification Reaction: ACID BASE SALT Fat or Oil + Na. OH Soap + Glycerol (Triglyceride) (lye or sodium hydroxide) CH 2 – OH + 3 Na. OH + CH – OH CH 2 – OH
