1. Chapter 14: Solutions Many of the forces we’ve talked about occur between ions/molecules in solutions Definition: A homogeneous mixture (only one phase) Examples: saltwater, tap water, gemstones, brass, air Made up of a solvent and a solute: Solvent: the substance present in the larger amount. Solute: the other substance Dissolving depends on attractive forces and entropy

2. Solutions There is a maximum amount of any solute that will dissolve in a given solvent If less than the maximum has been added, solution is unsaturated If the max or more than the max has been added, solution is saturated The concentration of a solution is the amount of solute that has been dissolved in a solvent. Many units of concentration: molarity (mol/L), weight % (g/g), ppm (mg/L)

3. Solubility If a solute will dissolve in a solvent, it is soluble. Some solutes have limits, some are infinitely soluble in a solvent. Sugar: 200 g in 100 mL water at 20 ºC Ethanol: infinitely soluble in water Gases are infinitely soluble in one another

4. Trends and Control of Solubility General rules: 1. polar solutes dissolve in polar solvents 2. nonpolar solutes dissolve in nonpolar solvents “Like dissolves Like” Oil and water don’t mix: is oil polar or nonpolar? You try: which of these will dissolve in water? CH 3 OH CH 3 CH 3 NH 3

5. Trends and Control of Solubility What controls Solubility: Enthalpy (enthalpy of solution) negative if new forces are stronger than original forces Entropy more complicated

6. “Forcing” Solubility How do you make something dissolve if it is normally insoluble in a solvent? Grease and grime are made up of nonpolar compounds. Will they dissolve in water? They will dissolve in nonpolar solvents, like turpentine, gasoline. Good for cleaning hands? Soap: the substance that makes nonpolar compounds dissolve in water. How would you design a soap molecule? What chemical properties should it have?

7. Soap and Detergent Soap is both polar and nonpolar Attracted to water (polar) and grime (nonpolar) Soap is the salt of a fatty acid, it is a surfactant molecule. hydrophobic end hydrophilic end

8. Soap Soap is both polar and nonpolar Attracted to water (polar) and grime (nonpolar) Made from fats, which contain 3 fatty acids and glycerol

9. Soap Nonpolar end is attracted to grime Polar end is attracted to water Dirt is picked up off clothes, skin, and rinsed away See: Soap movie

10. Soap Hard water and soap Hard water contains high concentration of Ca 2+ and Mg 2+ ions Ion-ion forces between Ca 2+, Mg 2+ and soap anion results in soap scum (soap forms a solid compound on your skin, bathtub, etc.) Water softeners replace Ca 2+, Mg 2+ with Na + How does dry-cleaning work? Previously used CCl 4, now less carcinogenic solvents

11. Fabric Softener: Cationic Surfactants What effect will softener use have on absorptivity? without with

12. Introduction to Polymers Polymers are long molecules made of repeating units, called monomers. In general: Specific example:

13. Forces between polymer chains: Crosslinks Weak: Intermolecular force crosslinks Strong: Colvalent bond crosslinks

14. Cotton Cellulose polymer Absorbs water. Cellulose chains crosslinked by H-bonding.

15. Wrinkling

16. Chemical crosslinking agent. Permanent Press Cotton