ch.13 -sec4

1. Chapter 13: Section 4 How are a liquid's properties changed by solutions?

2. Objectives: -> Define: Colligative Properties -> Explain: Why a liquid's boiling point is elevated but its freezing point is depressed when a solute dissolves. ->Describe: How the magnitude of a colligative property depends on the amount of solute and on the chemistry of the dissolution process. ->Compare: and contrast the roles of emulsifiers and surfactants. ->Explain: What hard water is and why its occurrence makes detergents superior to soaps.

3. Vocab -> Boiling-point elevation: The difference between the boiling point of a solution and that of the pure solvent -> Freezing-point depression: The difference between the freezing point of a pure solvent and that of a solution -> Colligative Property: A physical property that is dependent on the number of solute particles present rather than on the identity of those particles -> Emulsion: Colloidal-sized droplets (100nm in diameter) of one liquid suspended in another liquid

4. Vocab. (continued) -> Emulsifier: A substance that stabilizes an emulsion by forming a layer between two immiscible liquids -> Soap: A sodium or potassium salt of a long-chain fatty acid -> Micelle: A spherical arrangement formed by molecules of fat substances in an aqueous environment -> Surfactant: A class of salts, valued for their cleansing properties. -> Detergent: A surfactant other than a soap

6. The physical properties of H2O are changed when it dissolves substances.

7. For Example: Salt is added to icy sidewalks/streets to melt the ice.

8. The salt actually lowers the freezing point of water because it’s able to melt at a lower temperature than it normally would.

10. For Example: Salt is added to a cooking pot with pasta, which speeds up the cooking process.

11. Adding salt to the water elevates its boiling point. Salted water boils at a higher temperature.

13. Any physical effect of the solute on the solvent is a colligative property.

14. Freezing-Point depression and boiling-point elevation are examples of a colligative property.

16. Surfactants