Liquid Chemicals: Surface-Active Agents - Video Tutorials & Practice Problems

Liquid Chemicals: Surface-Active Agents

in this video, we're going to begin our lesson on the use of surface active agents or surfactants as liquid chemicals for controlling microbial growth. And so surface active agents are commonly referred to as just surfactants. And so these surface active agents, or surfactants are really just chemical agents that lower the surface tension of a liquid or solid in which they have been dissolved. And so these surface active agents or surfactants, they actually consist of antipathy molecules themselves. And so recall from our previous lesson videos that the term antipathy like means that the molecule contains both hydra filic and hydrophobic groups. In fact, these surfactant molecules have a hydra filic head and a long hydrophobic tail group. And so if we take a look at our image down below, notice that these molecules that you see here are the surfactant molecules and notice that they have once again a head group and they have a tail group branching off and notice that uh the head group is hydra filic, it is going to have either a positive or a negative charge on it. And so it will be able to associate with water and notice that this is water right here. And so when we add these surfactant molecules to water, they actually take this particular orientation where the hydra filic heads are all facing towards the water. And the hydrophobic tails are going to be facing towards the air here because they're going to associate with the surface of the water. And so through the addition of enough surfactant molecules, it actually allows for something known as a my cell to form. And in my cell is really just a spherical shape group of antipathy molecules as you can see down below this structure right here is the myself. And so notice that these surfactant molecules when enough have been added, they will associate with each other to form this myself and this myself is going to create a hydrophobic core right here in the middle and so the hydrophobic tails are all facing towards each other to create a hydrophobic core. And the hydra filic heads are all facing towards the outside and interacting with the water. Now usually water and oil do not mix very well together. However, with the use of these surface active agents and surfactants and adding enough to form my cells, these my cells can allow for hydrophobic substances like oil for example, to be mechanically washed away using polar solvents like water. And so what we'll see moving forward in our course, we're gonna be talking about two main types of surfactants. We're going to talk about soaps which are one main type of surfactant. And then we're also going to talk about detergents, which are another type of surfactant and a specific type of detergent that we'll talk about. Our squats which are really quaternary ammonium compounds that we'll get to talk more about moving forward in our course. But ultimately what happens is through the formation of these my cells, hydrophobic substances like oil can get trapped in the hydrophobic core and then water can wash away the entire my cell to get rid of that oil. And so these my cells can also trap bacteria as well and other substances as well to help wash away microbes and help to control microbial growth. And so this year concludes our brief introduction to surface active agents or surfactants. And we'll be able to learn more about them and talk more about different types of surfactants, including soaps, detergents and quotes as we move forward in our course. So I'll see you all in our next video

Soaps & Detergents

in this video, we're going to continue to talk about surface active agents or surfactants by briefly introducing soaps and detergents. And so 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 ions or potassium ions. Now 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 and this is because soaps are very, very effective. De Germ ear's, which really just means that soaps are very, very effective 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. Now, occasionally the soaps can be mixed in with antimicrobial. So sometimes you'll find antimicrobial soaps in the store, but again, the soaps on their own are not antimicrobial and they do not kill microbes, but they are really, really good at de german 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. Now, one of the disadvantages of soaps is that soaps tend to form what is known as soap scum. And this soap scum can form when the soap interacts with many minerals and salts that are found in hard water. And so this soap scum that tends to form when it interacts with hard water can actually deteriorate fabrics and ruin clothing and some surfaces. And so soaps are not always going to be the best free agent to use. And so we don't use soaps generally to wash our clothes. And so this is when detergents can come into play and we know that we use detergents to wash our clothes. And so detergents. Unlike soaps which are biodegradable, detergents are non biodegradable. And instead of being natural surfactant molecules, detergents are actually synthetic surfactant molecules that are generally going to be made in a lab. But really these detergents are gonna have lots of similarities to the soaps as you'll get to see down below in our image. But one of the big differences is that the soaps again are going to be fatty acids. However, the detergents are not fatty acids. Instead, these detergents are generally going to be associated with cell phone eight groups and the Sultanate group is really just this functional group that you can see highlighted down below in our image. Now, this cell phone, a group is actually less likely to bind minerals and salts and hard water, which means that the Sultanate group or the detergent on the cell phone, A group is not going to form a scum. And this means that detergents are not going to deteriorate fabrics and they will not ruin clothing and surfaces like what soaps might do. And so detergents can sometimes be a counter uh use to soaps. And so we use detergents to wash our clothes uh and we use soaps to wash our hands. Now these detergents, they can either be an ionic meaning that they can contain negatively charged groups, such as the Sultanate group that you see down below in our image. Or these detergents could be catatonic, meaning that they have positively charged groups and an example of a positively charged or catatonic detergent, our squats or quaternary ammonium compounds, which we'll get to talk more about in a different video as we move forward in our course. But for now, if we take a look at our image down below, we'll be able to better distinguish between the soaps and detergents. And so notice that the top half of our image here is focused on the soap molecule. And again, the soap molecule is really just a fatty acid. So it's this long hydrocarbon chain with a car box silic acid group at the end. And again, these soaps tend to form uh interactions with these salt atoms such as sodium and or potassium. And so here what you can see is a bar of soap. And again, the soap itself is not an antimicrobial, but it is effective at d germ ng, 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 down below in the bottom half of the image. We're showing you a detergent molecule. And so at first glance, the detergent molecule looks very similar. So you'll notice it has this long hydrocarbon chain, however, notice that it is not a fatty acid, so it does not have a carb oxalic acid group at the end, like what the soap molecule has. Instead, the detergent molecule has these other chemical groups that includes the softening group that you see right here and again. The detergent is not going to form a scum and so the detergent will not deteriorate fabrics and it will not ruin clothing and services like what soaps can do occasionally. And so over here we're showing you the detergents that you might use to wash your clothes. And so this year 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

Which of the following statements are FALSE?

• A. Soaps are made from organic materials like animal fats.
• B. Detergents are made from synthetic materials.
• C. Soaps interact with salt molecules in water which leaves a residue after washing.
• D. Soaps and Detergents kill microbes and are effective sterilants.
• E. All of the following are true.

Quats

in this video, we're going to continue to talk about surface active agents or surfactants by specifically introducing squats. And soak watts is really just an abbreviation for quaternary ammonium compounds. And soak watts or quaternary ammonium compounds are really just cat ionic detergents and what this means is that these are detergents that have a positive charge associated with them. And so these squats or quaternary million compounds are cat ionic detergents that are actually safe enough to be used in food preparation. Now these squats or quaternary ammonium compounds are anti pathetic molecules which once again recall from our previous lesson videos just means that they have both hydrophobic groups that are water fearing and hydrophobic groups that are water loving. And so, taking a look at this image down below, notice that we're focusing in on these quaternary ammonium compounds or these squats. And notice over here on the left hand side we're showing you a quat molecule and notice that it is an antipathy molecule because it has this hydrophobic tail group that is water fearing. And then it also has this hydra filic head group which is actually a quaternary ammonium group. And so these quads are antipathy molecules that have a positively charged quaternary ammonium group. Now these squats, they do actually have anti microbial features, which means they have the ability to destroy or kill microbes. And this is because these squats or quaternary ammonium compounds have the ability to disrupt cytoplasmic membranes and they can do that by inserting into the fossil lipid Byler. And so if we take a look at this image down below notice that we're showing you a plasma membrane being disrupted by these quat molecules that are found here. And these quite molecules are disrupting the fossil lipid bi layer from associating as it normally would and so therefore it can create these leaks and um the membranes and ultimately destroy the microbe. And so this year concludes our brief introduction to squats, these positively charged or cat ionic detergents, and we'll be able to get some practice applying these concepts as we move forward, so I'll see you all in our next video.

Quaternary ammonium compounds:

• A. Are cationic detergents that help wash surfaces.
• B. Are used as a 22% aqueous solution.
• C. Are extremely toxic to humans.
• D. Are amphipathic molecules with negatively charged hydrophilic portion.