Additionally, surfactants have the ability to form micelles, which are a type of molecular “cage” that forms around solute molecules that are normally immiscible in a particular solvent (ie nonpolar molecules can be protected inside a micelle when immersed in a polar solvent).įrom a chemical perspective, surfactants solve the incompatibility between waterĪnd oil because they contain both polar and nonpolar properties, serving as a bridge between polar/aqueous and nonpolar/organic substances. In the case of water-oil interface, adding a surfactant will lower the energy barrier for breaking hydrogen bonds among water molecules, and allow more freedom for water molecules to interact with other types of molecules in a given system. Surfactants are molecules or molecular compounds that lower the surface tension at an interface (interfacial tension). How can we lower the energy barrier to prevent separation? The answer lies in the addition of emulsifying agents, also known as surfactants. However, there are many contexts that require the stabilization of oil and water mixtures. We might shake vigorously to mix oil and water together, but for the reasons mentioned above, the mixture will quickly separate into two distinct phases. This is true for the water and oil components that we are working to combine in a lotion. This is because vinegar and oil are chemically incompatible. In the case of lotions, we can employ a tool such as a stick blender.Īnyone who has combined oil and water knows that, regardless of how much you mix and shake, the vinaigrette will quickly separate into the oil phase (top) and water phase (bottom). To effectively combine water-based vinegar with oil, we might use a whisk or blender. Another example of this type of mixture lies in the kitchen when making a vinaigrette. This typically requires a rigorous mechanical force to shear and disperse one liquid into the other. In creating lotion emulsions, we are combining oil-based liquids and water-based liquids such that the end product appears as a uniform substance. An emulsion is a specific type of colloid because all the components of an emulsion are liquids. Emulsions are a specific type of colloid, or a mixture where microscopic particles are dispersed - without being dissolved - throughout another substance.
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