Module 7 - Organic Chemistry Flashcards
What is a surfactant?
Surface acting agent: A substance which lowers the surface tension of a liquid
What is an emulsifier?
A substance which allows two normally immiscible liquids to mix
What is an emulsion?
A mixture of two normally immiscible liquids
Structure of soaps
Made from fatty acids, they have an hydrophilic polar Na/K head and hydrophobic non-polar hydrocarbon tail.
Structure of anionic detergents
Negatively charged ion head and hydrophobic carbon tail
Structure of cationic detergents
Positively charged ion head
Structure of non-ionic detergents
Head is uncharged but is still polar
Cleaning action of soaps
The surfactant orients with tails sticking into the non-polar substance (grease) and the head faces outwards to the water. The surface is agitated (through scrubbing), lifting off the grease, forming spherical micelles which repel each other due to the layer of charge, forming an emulsion which can be washed away.
Soap in hard water
Forms a precipitate (scum) with Ca2+ and Mg2+
Anionic detergents in hard water
Relatively effective in hard water
Cationic and non-ionic detergents in hard water
Not affected by hard water
What is a polymer?
A giant molecule with repeating units
What is a monomer?
Molecules that when linked together form a repeating structure
What is an addition polymer?
Alkene monomers are bonded without the loss of molecules
Process of addition polymerisation.
Initiation - Breaking of double bond to form to form free radicals
Propagation - Activated monomer reacts further with other ethylene
Termination - Two free radicals combine to form a stable molecule
Structure, properties and uses of polyethylene
Made of ethylene. Low density (LDPE) has many side branches making it soft and flexible being used in plastic bags. High density (HDPE) has limited side-branching making it stronger and rigid used in containers
Structure, properties and uses of polyvinyl chloride
Made of vinyl chloride monomers with a Cl every two branches. Rigid due to large Cl and brittle (but plasticiser can reduce this) so it used in piping
Structure, properties and uses of polystyrene
Made of styrene that alternates between each CH. Expanded polystyrene is low density and a good thermal insulator used in disposable cups. Crystalline polystyrene is rigid and transparent so used in CD cases
Structure, properties and uses of poly tetrafluoroethylene
Made of ethylene with 4 F. PTFE is heat resistant and has a high melting point so it used in teflon fry pans
What is a condensation polymer?
The formation of polymers which also produces another small molecule (usually water)
Structure, properties and uses of polyamides
When amines and carboxylic acids react to produce an amide. Nylon has high tensile strength and waterproof so is used in clothes, carpets and umbrellas
Structure, properties and uses of polyesters
When alcohols and carboxylic acids form esters. It is resistant to water so often used in plastic bottles
