Module 7 - Organic Chemistry

Question 1

What is a surfactant?

Answer 1

Surface acting agent: A substance which lowers the surface tension of a liquid

Question 2

What is an emulsifier?

Answer 2

A substance which allows two normally immiscible liquids to mix

Question 3

What is an emulsion?

Answer 3

A mixture of two normally immiscible liquids

Question 4

Structure of soaps

Answer 4

Made from fatty acids, they have an hydrophilic polar Na/K head and hydrophobic non-polar hydrocarbon tail.

Question 5

Structure of anionic detergents

Answer 5

Negatively charged ion head and hydrophobic carbon tail

Question 6

Structure of cationic detergents

Answer 6

Positively charged ion head

Question 7

Structure of non-ionic detergents

Answer 7

Head is uncharged but is still polar

Question 8

Cleaning action of soaps

Answer 8

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.

Question 9

Soap in hard water

Answer 9

Forms a precipitate (scum) with Ca2+ and Mg2+

Question 10

Anionic detergents in hard water

Answer 10

Relatively effective in hard water

Question 11

Cationic and non-ionic detergents in hard water

Answer 11

Not affected by hard water

Question 12

What is a polymer?

Answer 12

A giant molecule with repeating units

Question 13

What is a monomer?

Answer 13

Molecules that when linked together form a repeating structure

Question 14

What is an addition polymer?

Answer 14

Alkene monomers are bonded without the loss of molecules

Question 15

Process of addition polymerisation.

Answer 15

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

Question 16

Structure, properties and uses of polyethylene

Answer 16

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

Question 17

Structure, properties and uses of polyvinyl chloride

Answer 17

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

Question 18

Structure, properties and uses of polystyrene

Answer 18

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

Question 19

Structure, properties and uses of poly tetrafluoroethylene

Answer 19

Made of ethylene with 4 F. PTFE is heat resistant and has a high melting point so it used in teflon fry pans

Question 20

What is a condensation polymer?

Answer 20

The formation of polymers which also produces another small molecule (usually water)

Question 21

Structure, properties and uses of polyamides

Answer 21

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

Question 22

Structure, properties and uses of polyesters

Answer 22

When alcohols and carboxylic acids form esters. It is resistant to water so often used in plastic bottles