Chapter 15.2 Homogeneous Aqueous Systems Chapter 15.3 Heterogeneous Aqueous Systems

Chapter 15.2 Homogeneous Aqueous Systems Chapter 15.3 Heterogeneous Aqueous Systems

Learning Objectives Understand the “s” words and how they are different from each other (solution, solvent, solute) Understand the process of solvation of ions “Like dissolves like” and the difference between polar and non-polar molecules when it comes to solvation. Electrolyte versus non-electrolyte Solutions vs. colloids vs. suspensions

Solution (aq) – water that contains dissolved substances Solvent – The dissolving medium of the solution (water in this chapter) Solute – The solid that gets dissolved Solvent plus solute = solution

When a substance becomes solvated by water, we say it is soluble in water Chemists use the axiom “like dissolves like”: Polar substances tend to dissolve in polar solvents. Nonpolar substances tend to dissolve in nonpolar solvents.

All ionic compounds are electrolytes because they break apart into ions when added to water

The next part of the textbook is about hydrates … we will skip for the upcoming TWIZ We did do a lab where we heated a hydrate CuSO4 . 5H2O and determined how much water was released in moles.

It is a type of homogeneous aqueous system known as a colloid. The JELL-O mystery … what the heck is it? It is a type of homogeneous aqueous system known as a colloid. JELL-O is a kind of strange substance which is a colloid. JELL-O is made from water with flavorings, sweetener, and gelatin mixed in. Gelatin is made from a protein called collagen which is the main protein in cartilage, the flexible material that forms your outer ear and nose. When JELL-O is added to hot water, the long collagen molecules separate from each other and mix throughout the water. But when this mixture is cooled, the collagen molecules link up with each other in a different way, forming a 3-dimensional network. Water molecules get trapped in the network and help give JELL-O its more wiggly characteristics.  (adapted from ACS website) More info about colloids

Particles are 1 nm – 1000 nm

Example of a emulsion while doing chemistry

Tyndall Effect Colloidal suspensions can scatter rays of light This phenomenon is known as the Tyndall effect

Summary Type of Aqueous System Can you see the solute? Particle Size Does it scatter light? Solution Homogeneous (Evenly dispersed) No < 1 nm Colloid Between 1 nm and 1000 nm Yes Suspension Heterogeneous (Unevenly dispersed) > 1000 nm Depends on size of particles and how they are dispersed