Surfactants

Question 1

Define a colloidal system

Answer 1

When the molecules dispersed within a medium what have a dimension between 1 and 1000nm, such systems are described as microheterogenous.

Question 2

Contrast a colloid vs suspension.

Answer 2

Suspension particles are larger >1um, meaning they may be visible to the eye unlike colloids. Dispersed particles are non-soluble, this also means suspensions are more likely to sedimentate. Suspensions can be filtered unlike colloids.

Question 3

Define CMC

Answer 3

point of which the surface is fully saturated with surfactants and micelles start to form.

Question 4

Why do micelles form?

Answer 4

1. Hydrocarbon chains prefer to be in contact with each other than with water.
2. Water molecules prefer to be in contact with each other rather than have hydrocarbon chains wedged between them
3. There may also be an entropic effect from the hydrocarbon chains having more freedom of movement in a micelle interior than in solution.

Question 5

At concentrations below 40% (by mass) what structure is formed?

Answer 5

micelle

Question 6

spherical vesicle structures called

Answer 6

liposome

Question 7

At high concentrations surfactants form other bilayer structures such;

Answer 7

bilayer sheet, or cylinders.

Question 8

How does grease get “carried away” by surfactants?

Answer 8

inside micelle.

Question 9

Size of micelle?

Answer 9

2-20nm