Association Colloids and Micelle Shapes

What is the term used to describe the point at which micelles start to form in a solution?

Below the CMC, amphiphiles adsorb at the air-water interface and form a monolayer.

What happens to the surface tension of a solution when amphiphile concentration increases below the CMC?

What happens to the surface tension of a solution when the CMC is reached?

In water, in which direction do the hydrocarbon chains of micelles face?

What is the type of micelles that form in nonpolar liquids?

At what concentration do laminar micelles usually form?

Spherical micelles can exist in equilibrium with laminar micelles.

What is the term used to describe the ions that are attracted to the surface of an anionic micelle?

What types of interactions can occur between association colloids and insoluble or slightly soluble materials?

What type of surfactants are commonly used as solubilizers?

Which of the following is NOT a possible type of amphiphile?

Association (Amphiphilic) Colloids

Amphiphiles adsorb at the air-water interface, forming a monolayer. Adsorption increases with amphiphile concentration, which leads to a decrease in surface tension.
When the concentration of amphiphiles reaches a critical micelle concentration (CMC), micelles form in the bulk phase. Further increases in concentration do not decrease surface tension.
A plot of surface tension against the logarithm of surfactant concentration shows a sharp change at the CMC.

Micelle Shapes

Micelles in water: Hydrocarbon chains face inward, while polar heads associate with water.
Reverse micelles in nonpolar liquids: Polar heads face inward, and hydrocarbon chains interact with the nonpolar solvent.
Laminar micelles: Formed at higher amphiphile concentrations. These exist in equilibrium with spherical micelles.

Amphiphile Types

Amphiphiles can be anionic, cationic, nonionic, or ampholytic (zwitterionic).
- If anionic, counter-ions (gegenions) associate to reduce the overall negative charge.

Solubilization

Association colloids, like micelles, increase the solubility of insoluble/slightly soluble materials.
This is called solubilization.
Properties like absorption, bioavailability, activity, and stability can be affected by solubilization.
Nonionic surfactants are common solubilizers due to their low toxicity.

This quiz covers the properties and behaviors of amphiphilic colloids, including how amphiphiles adsorb at interfaces and form micelles. It explores the effects of concentration on surface tension and the different shapes of micelles in various solvents. Test your understanding of amphiphile types and their structural characteristics.