1. A wide range of cleaning products are made from colloids and surfactants.
* State the relationship between the properties of an emulsion and the types of molecules present.
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. | |
Oil-based (water-in-oil) emulsions, such as cold creams, night creams and hair creams, contain some water. These are not miscible with water and so if a small amount is placed into water, the emulsion will not be maintained. They are useful to cleanse the skin, moisturise very dry skin and hold hair in place, but are greasy and sticky to the touch. The types of surfactant molecules present in water-in-oil based emulsions are long starch molecules or protein chains. The chains wind among minute water droplets and prevent them from merging together. | |
* Outline the purpose of the emulsifying agent in a range of consumer cleaning products.
The molecules in emulsifying agents that are used in dishwashing and laundry detergents (anionic) have a negative end when they dissolve. This allows them to keep oily substances away from any article that has negatively charged surfaces, such as glass and crockery. The molecules in emulsifying agents that are used in fabric softeners...