Colloids and Suspensions

Particles and Mixtures

• Particles in a suspension are larger than atoms and can settle out of solution.
• Colloids are heterogeneous mixtures of intermediate-sized particles (between atomic-scale size of solution particles and suspension particles).
• Colloid particles are between 1 nm and 1000 nm in diameter and do not settle out.

Characteristics of Colloids

• The most abundant substance in a colloid is the dispersion medium.
• Colloids are categorized according to the phases of their dispersed particles and dispersing mediums.
• The dispersed particles in a colloid are prevented from settling out due to polar or charged atomic groups on their surfaces.

Electrostatic Layers in Colloids

• The polar or charged areas on the surface of dispersed particles attract the positively or negatively charged areas of the dispersing-medium particles.
• This results in the formation of electrostatic layers around the particles.
• The electrostatic layers repel each other when the dispersed particles collide, keeping the particles in the colloid.

Factors Affecting Colloids

• Interfering with the electrostatic layering can cause colloid particles to settle out of the mixture.
• Stirring an electrolyte into a colloid can cause the dispersed particles to clump together, destroying the colloid.
• Heating a colloid can destroy it by giving colliding particles enough kinetic energy to overcome the electrostatic forces and settle out.

Examples of Colloids

• Milk is a colloidal emulsion, with liquid particles dispersed in a liquid medium.
• Other types of colloids are categorized according to the phases of their dispersed particles and dispersing mediums.

This quiz covers the properties and characteristics of colloids and suspensions, including their particle sizes, settling behavior, and composition. It also includes examples of colloids, such as milk.