In this video, we're going to continue to talk about surface active agents or surfactants by briefly introducing soaps and detergents. Soaps can be defined as biodegradable natural surfactant molecules that are actually fatty acids, and they contain a salt atom or an atom that tends to form salts, such as, for example, sodium or potassium ions. It's important to note that soaps alone are not antimicrobials, which means that soaps alone do not kill microbes. However, soaps can still be very effective at controlling microbial growth because soaps are very effective degermers, which means that soaps are very good at removing microbes from the surface of an object, such as removing microbes from the surface of your hands when you wash your hands with soap. But again, the soaps on their own do not kill microbes.
Occasionally, soaps can be mixed with antimicrobials, so sometimes you'll find antimicrobial soaps in the store. But again, the soaps on their own are not antimicrobial and do not kill microbes, but they are really good at degerming or removing microbes from the surface, allowing those microbes to be washed away, such as being washed down a drain when you wash your hands. One of the disadvantages of soaps is that soaps tend to form what is known as soap scum. This soap scum can form when the soap interacts with many minerals and salts found in hard water. This soap scum, which tends to form when it interacts with hard water, can deteriorate fabrics and ruin clothing and some surfaces. So, soaps are not always going to be the best reagent to use, and so we don't generally use soaps to wash our clothes.
This is when detergents can come into play. We know that we use detergents to wash our clothes. Unlike soaps, which are biodegradable, detergents are non-biodegradable. Instead of being natural surfactant molecules, detergents are synthetic surfactant molecules that are generally made in a lab. But these detergents have lots of similarities to soaps. One of the big differences is that soaps are fatty acids, whereas detergents are not fatty acids. Instead, these detergents are generally associated with sulfonate groups, a functional group that is less likely to bind minerals and salts in hard water, which means that the sulfonate group or the detergent with the sulfonate group is not going to form scum. This means that detergents will not deteriorate fabrics and will not ruin clothing and surfaces like soaps might do occasionally.
Detergents can be a counter use to soaps. We use detergents to wash our clothes, and we use soaps to wash our hands. These detergents can either be anionic, meaning that they contain negatively charged groups such as the sulfonate group, or they could be cationic, meaning that they have positively charged groups. An example of a positively charged or cationic detergent is quaternary ammonium compounds, which we'll get to talk more about in a different video as we move forward in our course.
For now, if we take a look at our image down below, we'll be able to better distinguish between the soaps and detergents. Notice that the top half of our image is focused on the soap molecule, which is a long hydrocarbon chain with a carboxylic acid group at the end. These soaps tend to form interactions with salt atoms such as sodium and potassium. Here, you can see a bar of soap, and again, the soap itself is not an antimicrobial but is effective at degerming, allowing us to wash our hands with soap and remove the microbes from the surface so that those microbes can be washed away, such as being washed down a drain.
Now, the bottom half of the image shows a detergent molecule. At first glance, the detergent molecule looks very similar. However, notice that it is not a fatty acid, so it does not have a carboxylic acid group at the end like what the soap molecule has. Instead, the detergent molecule has other chemical groups that include the sulfonate group that you see right here. Again, the detergent will not form a scum, and so the detergent will not deteriorate fabrics and will not ruin clothing and surfaces like what soaps might occasionally do. Here we are showing you the detergents that you might use to wash your clothes.
This concludes our brief introduction to soaps and detergents, and we'll be able to get some practice applying these concepts and learn more as we move forward in our course. So, I'll see you all in our next video.