Part 2: Colloids and Surfactants Lifestyle Chemistry Part 2: Colloids and Surfactants

State the relationship between the properties of an emulsion and the types of molecules present

Emulsions Vocabulary An emulsion is a mixture of tiny droplets of one liquid dispersed in another in which it is immiscible. Emulsification is the process of dispersing a liquid in another liquid in which it is immiscible as a stable colloidal dispersion. An emulsifying agent is a substance added to a mixture to stabilise an emulsion.

Properties of Emulsions Two Types of Emulsions: 1 Oil in Water Oil molecules are dispersed in water. Water evaporates more readily from the emulsion. This emulsion can be dyed by water-soluble dyes, such as food colouring.

Properties of Emulsions Two Types of Emulsions: 2 Water in Oil Water molecules are dispersed in oil, therefore the water evaporates less quickly. This emulsion can be dyed with oil-soluble dyes, such as fuchsin. Oil has a higher electrical resistance than water. For this reason, a water-in-oil emulsion is a relatively poor electrical conductor.

Properties of Emulsions Two Types of Emulsions:

Emulsions Surfactants are emulsifiers but not all of them are good ones. Non-ionic surfactants do not have very polar heads and don’t emulsify well. Good Emulsifiers (Are polar) Bad Emulsifiers (only slightly polar) Anionic Amphoteric Cationic Non-Ionic

Outline the purpose of the emulsifying agent in a range of consumer cleaning products. Identify that soaps and detergents are emulsifying agents and surfactants Explain why cleaning agents must be surfactants and emulsifiers

Emulsions Oils do not dissolve in water well (they are immiscible). Emulsifiers stabilise oil broken up into smaller globules when the oil is shaken with water. The emulsifiers then hold the oil globules in water, preventing them from forming larger globules or floating to the surface.

Role of Emulsifier in detergent Diagram

Cleaning Agents Cleaning agents must be both surfactants and emulsifiers. Being surfactants they concentrate at surfaces orientating their polar end in the most polar liquid and their non-polar chain in non-polar liquid. Being emulsifers, cleaning agents surround the liquid globules, keeping them dispersed and stopping them from joining up with other globules. This enables the dispersed globules to be washed away.

Define the term biodegradable Discuss the biodegradability of soaps and soapless detergents

Biodegradability Vocabulary Biodegradable means an organic substance capable of being decomposed by the action of naturally occurring organisms.

Biodegradability of Soaps Soap is made from renewable natural resource and is biodegradable, this means it can be broken down into simple molecules (H2O & CO2) by bacteria in the environment.

Biodegradability of Detergents First Generation Detergents (60s-70s) Better cleaning action. Early Detergents were harmful to the environment as they were synthetic and only slowly biodegradable. Accumulated in lakes, rivers and sewage treatment plants. Led to frothing and bubbling of water ways.

Biodegradability of Detergents Second Generation Detergents Quickly biodegradable Expensive so phosphates added to reduce expense. The phosphates could hold calcium, magnesium and iron ions in suspension, preventing a scum from forming. Added a lot of phosphates to waterways.

Biodegradability of Detergents Detergents Today Surfactants must degrade quickly and not cause damage to the environment and living things.

Importance of Biodegradability May lower surface tension of outer layers of living tissue Accumulate in the food chain reaching hazardous levels Pond skaters may die if can’t sit on water since surface tension has changed Disrupt normal functioning of living things since the chemicals may affect their hormones