Emulsions

Question 1

Define emulsion

Answer 1

Dispersion of one immiscible liquid in another immiscible liquid

Question 2

What 2 phases does an emulsion contain?

Answer 2

It contains an oily and aqueous phase

Question 3

Define creaming

Answer 3

Oil droplets travel to the top of the liquid

Question 4

Define cracking

Answer 4

Coalescence of droplets forming 2 distinct layers

Question 5

Outline the structure of a surfactant

Answer 5

It contains a hydrophilic head which solubilises polar molecules and a hydrophobic tail which solubilises non-polar substances

Question 6

Define CMC (critical micelle concentration)

Answer 6

The conc. of surfactants that allow for micelle formation

Question 7

Define rheology

Answer 7

The study of particle flow and deformation particularly liquids and semi-solids

Question 8

Define viscosity

Answer 8

fluid resistance to flow/movement

Question 9

Define plastic flow

Answer 9

• With increasing shear rate (i.e. the amount of force applied) there is flow of plastic (i.e. decrease in viscosity)
• involves a yield stress point (the particles will only flow when it reaches this point - permanently deform
  —> the line is on the left side of Newtonian flow (original line)
• example: long high molecular weight solutes

Question 10

Define pseudo-plastic

Answer 10

With increasing shear rate, viscosity decreases (similar to plastic flow)
- also known as shear thinning
–> the line is curved on the left hand side of Newtonian flow (original line)
(becomes less viscous, the harder you shake it)
- example: long high molecular weight solutes

Question 11

Define dilatant flow

Answer 11

With, increasing shear rate viscosity increases (i.e. becomes more viscous, the harder you shake it)