Emulsions Continued

Emulsions e.g. oil in water Oil droplets dispersed in water … coalesce to reduce surface tension … then float to surface (oil is less dense) Emulsions Emulsifiers (surfactants) stabilise a colloid by lowering surface tension Notes process and present diagrammatic information to describe the effects of soaps, skin cleansers and shampoos on the solubility of oil

Emulsions Emulsifiers have a polar head (hydrophilic and lipophobic)) have a non polar tail (hydrophobic and lipophilic) Non polar chain Polar head Add emulsifier to water/oil mix lipophilic chain attaches to oil particles water attracts the polar heads surface tension is lowered with oil dispersed Notes process and present diagrammatic information to describe the effects of soaps, skin cleansers and shampoos on the solubility of oil

Emulsions Oil Droplet in water (with emulsifier) Oil phase Stabilizing layer of hydrocarbon chains (hydrophobic) Polar (hydrophilic) heads Aqueous phase Notes process and present diagrammatic information to describe the effects of soaps, skin cleansers and shampoos on the solubility of oil

Emulsions Emulsifiers in food and the body typically polar lipids occur in membranes egg yolks (which contain lecithin) in crude fats and oils lecithin Notes process and present diagrammatic information to describe the effects of soaps, skin cleansers and shampoos on the solubility of oil

Emulsions Terms to Know Dispersed phase (the colloidal particles) Continuous phase (the dispersion medium) Micelle (A term frequently used for colloidal particle) Lipophilic (affinity for oils / fats) Hydrophilic (affinity for water) Emulsifier (A substance with affinity for both the colloid and the dispersion medium)

Types of Molecules in Emulsions An emulsion is a mixture of consisting of a liquid dispersed in a liquid. Microscopic droplets of one liquid remain suspended in the other. Types of molecules present typically are: water, hydrophilic compounds, oils, lipophilic compounds, emulsifiers, surfactants Properties of an emulsion components of the emulsion remain dispersed in each other i.e. the components do not separate out from each other emulsions in cosmetics give the cosmetics a desirable texture emulsions in some foods give the food a desirable texture e.g. mayonnaise has a smooth and creamy texture that is pleasant in the mouth Water-based (oil-in-water) emulsions, such as hand lotions, face cleansing lotions and conditioners, contain some oil or fat. They are used to moisturise or protect the skin and hair by placing oil onto the surface. They have a lubricating effect and provide sheen. These are miscible with water. This means that if a small amount is placed into water and shaken or stirred it will remain suspended. The types of surfactant molecules present in oil-in-water based emulsions are large molecules with very polar chemical groups at one end. This end becomes attracted to the polar water molecules. The other non-polar end of the surfactant is attracted to the non-polar oil molecules. Many of the surfactant molecules become positioned around the very small droplets of oil, preventing them from merging together. state the relationship between the properties of an emulsion and the types of molecules present

Types of Molecules in Emulsions Important emulsions include oil - water water- oil Molecules present in an oil-water or water-oil emulsion are non-polar fat molecules polar water molecules molecules of an emulsifier Bile, also called gall, is a bitter, yellow-green secretion of the liver, stored in the gallbladder, and released during digestion when fats enter the first part of the small intestine (duodenum). Bile emulsifies fats preparing them for further digestion and absorption in the small intestine. state the relationship between the properties of an emulsion and the types of molecules present

Emulsifying Agents in Cleaning Products Outline the purpose of emulsifying agents in a range of cleaning products (e.g. soaps, detergents, surface cleaning products) Emulsifying agents permit liquids that a normally immiscible to mix together and remain mixed. Emulsifying agents have molecules that have an affinity for both components of the emulsion. Cleaning products often contain polar and non-polar compounds - an emulsifying agent helps to keep such mixtures homogeneous. www.chemistry.co.nz/deterghist.htm outline the purpose of the emulsifying agent in a range of consumer cleaning products

Properties of Emulsions Oil and water are immiscible liquids. They are immiscible because the oil is not soluble in the water due to the polar nature of water molecules and the non-polar nature of oil molecules. Because the oil is less dense than the water, it floats on the surface of the water. If the mixture is shaken, the suspension produced separates back into layers readily. This is an effect caused by gravity. perform a first-hand investigation to prepare an emulsion and compare its properties to those of a solution and suspension

Properties of Emulsions Oil and water are immiscible liquids. The two layers can be seen in the test tube on the left. Soaps and detergents are emulsifying agents with an affinity for both polar water molecules and non-polar oils. The effect of adding detergent to an oil / water mixture can be seen in the image on the far right. (after shaking) www.chemistry.co.nz/deterghist.htm perform a first-hand investigation to prepare an emulsion and compare its properties to those of a solution and suspension

Emulsifying Agents in Cleaning Products Solution Suspension Emulsion Transparent Opaque when mixed but components may be clear after they separate on standing Remains opaque Homogeneous and stable over long time intervals Homogeneous when mixed thoroughly but separates on standing Homogeneous and stable over long periods and usually has a smooth texture perform a first-hand investigation to prepare an emulsion and compare its properties to those of a solution and suspension

Cleaning Agents N Cleaning agents must be surfactants because surfactants interact at the interface between two immiscible substances, creating an emulsion. Many cleaning agents form an emulsion between water and oils found in soiled items, permitting water to wash the oil-water emulsion formed away more readily. To be effective as cleaning agents, soap and detergents must be effective both as surfactants and emulsifiers. Not all emulsifiers are good cleaning agents, for example egg yolk provides the emulsifying agent for the oil and vinegar to make mayonnaise. [ref: http://hsc.csu.edu.au/senior_science/core/life_chem/9-2- 2/9.2.2.html] explain why cleaning agents must be surfactants and emulsifiers

Soaps and Detergents - Definitions Useful information about soaps and detergents can be found at www.edwardwillett.com/Columns/detergents.htm The above site has excellent historical material as well. Recommended reading! Also… http://www.cpchem.com/alphaolefins/applications/surfactants.asp http://www.chemistry.co.nz/deterghistory.htm Synthetic Detergents The term "synthetic detergent" is used throughout this article, for a material which cleans (or is used for cleaning), but in this definition soap is not included. Even so, this is still a wide definition, because, of course, it can refer to the active ingredient, or the solid, liquid, paste or powder compounded from this active matter. However, this should not lead to confusion, as the industry itself as yet makes no distinction in terminology between the basic material and the ready-for-use product. The first synthetic detergents which fall into our definition of the term seem to have been developed by the Germans in the First World War period to allow fats to be utilized for other purposes. These detergents were of the short-chain alkyl naphthalene sulphonate type, made by coupling propyl or butyl alcohols with naphthalene and subsequent sulphonation, and appeared under the general name of Nekal. These products proved to be only fair to moderately good detergents, but good wetting agents and are still being produced in large quantities for use as textile auxiliaries. In the late 1920s and early 1930s long-chain alcohols were sulphonated and sold as the neutralized sodium salts without any further additions except for sodium sulphate as an extender. In the early 1930s long-chain alkyl aryl sulphonates with benzene as the aromatic nucleus, and the alkyl portion made from a kerosene fraction, appeared on the market in the USA. Again, these were available as the sodium salts extended with sodium sulphate. Both the alcohol sulphates and the alkyl aryl sulphonates were sold as such as cleaning materials, but did not make any appreciable impression on the total market. At the end of the Second World War alkyl aryl sulphonates had almost completely swamped the sales of alcohol sulphates for the limited uses to which they were applied as general cleaning materials, but the alcohol sulphates were making big inroads into the shampoo field. An exception was Teepol, a secondary alcohol sulphate which remained popular for some years. In common, however, with other chemical developments during this century, progress was not in one direction only. The limiting factor is always the availability of raw materials in a particular country. Concurrently with the above developments, there were developed, both in Germany and the USA, the lgepon type of compounds of which lgepon-T, the sodium salt of oleyl tauride is an example, and in Germany the Mersolates, which are alkane sulphates. In the United Kingdom, Teepol, a secondary olefine sulphate from petrochemical sources, was manufactured in large quantities and is still being produced in England and western Europe to this day.

Soaps and Detergents - Definitions A soap is a salt of a fatty acid. A fatty acid is a long-chain carbon based molecule containing a –COOH group. Soaps are generally biodegradable. Soaps have the disadvantage of precipitating out in hard water and hence they will not produce a lather. Hard water is water containing dissolved minerals including magnesium and calcium salts (chlorides, nitrates) Source of soaps: fats from plant and animal sources Biodegradable substances can be decomposed by bacteria, fungi and other microorganisms. Pure soap is reasonably biodegradable, whereas detergents are less easily biodegradable. Soaps work well in water that does not contain dissolved ions. The use of soap in hard water results in a precipitate being formed that produces a “scum” in the water. Detergents do not precipitate out the ions in hard water. Detergents contain branched chains of carbon atoms, whereas soaps usually contain simple unbranched chains. This structural difference prevents bacteria that can decompose the unbranched molecules from using and breaking down the detergent molecules. The behaviour of most organic molecules is strongly influenced by their shapes. This is why artificial sweeteners can be made that have a part of their shape that makes them much sweeter than sugar (so less is needed) and another part of their structure makes them unable to be metabolised by enzymes in the digestive system. (e.g. Splenda®) identify that soaps and detergents are emulsifying agents and surfactants