1 Chapter 10 States of Matter

Essential Question What are physical & chemical properties of liquids and solids? Standard 2h Students will identify solids and liquids held together by forces, and to relate these forces with boiling and melting points. 2

Kinetic Molecular Theory (Ideal Gases) 1. Gases move continuously. 2. Particles extremely small. 3. Forces between molecules negligible. 4. Collisions are elastic (no loss of energy). 5. Average kinetic energy of gas particles same for all gases at same temperature. 3

4 Gases, Liquids and Solids Most gases monatomic. Small molecules with covalent bonding. Pure liquids composed of molecules with covalent bonding. All ionic compounds are solids. They conduct electricity when heated, melted or aqueous. Except for mercury, all metals are solid and conduct electricity.

5 The Liquid State Viscosity: resistance of a liquid to flow. Related to molecule shape. Small molecules have low viscosities. Large molecules have high viscosities.

6 Properties of Liquids Surface Tension: energy required to increase the surface area of a liquid. Liquids with stronger attractive forces have a greater surface tension (ex: H 2 O). A molecule in the middle of a liquid is attracted equally in all directions. Surface area minimized. Light objects float.

7 Surface Tension Detergents or surfactants can lower surface tension, causing water to wet a surface. This allows cleaning agent to “bind” to dirt molecules and carry away. Hg pure H 2 O H 2 O with detergent

8 Boiling Point Liquid heated; vapor pressure increases. Boiling point (B.P.) = vapor pressure = external pressure Normal boiling point = temp where vapor pressure of a liquid = 1 atm.

9 Classification of Solids Ionic solids - ions at lattice point in crystal. Molecular solids - molecules at each lattice. Covalent network solids - atoms at lattice points; covalent bonds. Ex: graphite & diamond.

10 Graphite, an Allotrope of Carbon

11 The Structure of Diamond, an Allotrope of Carbon

12 Vaporization and Condensation Vaporization: molecules of liquid break away and enter the gas phase. Condensation: molecules in gas phase enter the liquid phase.

13 Distillation In simple distillation, a solution of two volatile liquid compounds are heated to boiling. The more volatile component is in higher concentration in the vapor than in the liquid. Separation technique for liquids.

14 Distillation Apparatus

15 Melting and Freezing When solid is heated, particles vibrate more vigorously and become liquid. This process is called melting. When a substance changes from a liquid to a solid the process is called freezing.

16 Water Water is a unique substance. Molecular bonding consists primarily of hydrogen bonds which are quite strong. Relatively high boiling point (100 o C) and melting point (0 o C) Moderate density (~1 g/mL) High Specific Heat (4.184 J/g) High Heat of Vaporization

17 Properties of Water High surface tension High capillarity (Hydrogen bonds). Adhesion > cohesion. Density of liquid > solid ice floats Due to hydrogen bonding, open structure of ice.

18 Solvent Properties of Water Highly polar, able to form hydrogen bonds. Good solvent for ionic compounds.