Liquids & Solids

1. Liquids & Solids

2. Objectives 12-1 • describe the motion of particles of a liquid and the properties of a liquid using KMT • define and discuss vaporization • define and discuss freezing

3. KMT of Liquids FLUID - a substance that can flow and therefore take the shape of its container • Particles have lower KE than gases • Attractive forces between molecules is greater • More ordered than gases

4. Properties of Liquids • Relative to gases have a much higher density • Relatively incompressible • Can diffuse • Surface tension • (force that pulls molecules together giving a smaller surface area) • Capillary action – attraction between the surface of a liquid and a solid (meniscus) • Vaporization – changing from liquid to gas • Evaporation – particles escaping from the surface of a non-boiling liquid • Boiling – changing of liquid to bubbles of vapor that appear throughout a liquid • Freezing – change of a liquid to a solid by the removal of heat

5. Objectives 12-2 • describe the motion of particles of a solid and the properties of a solid using KMT • differentiate between crystalline and amorphous solids • describe crystal symmetry and define crystal structure and unit cell

6. KMT of Solids • Higher density than liquids • More ordered • Very strong intermolecular forces • London dispersion • Dipole-dipole • Hydrogen bonding • Crystalline solids (very organized) • Amorphous solids (not organized)

7. Properties of Solids • Definite shape and volume • Definite melting point • Supercooled liquids – amorphous solids have the ability to flow over a range of temperatures • High density/incompressibility • Low rate of diffusion

9. Crystalline Solids

10. Ionic Crystals • Cations and anions arranged in a pattern • Group 1 & 2 bonded with Group 16 & 17 • Hard and brittle • High melting points • Good insulators

11. Covalent network crystals • Single atoms bonded to its neighbor • Can be very large • Usually hard and brittle • High melting points • Non-conductors or semiconductors

12. Metallic crystals • Metal atoms surrounded by a sea of electrons • Good conductors • Melting points vary

13. Covalent molecule crystals • Covalently bonded molecules held together by intermolecular forces • If non-polar, only LDF (weak) • If polar, held together by LDF, dipole-dipole, and maybe hydrogen bonds • Low melting points • Relatively soft • Easily vaporized • Good insulators

17. Amorphous solids • “without shape” • Plastics and glass

18. Changes of State

19. Equilibrium • Dynamic condition in which two opposing changes occur at the same rate in a closed system

21. Equilibrium and Changes of State • Solid to liquid  melting • Solid to gas  sublimation • Liquid to solid freezing • Liquid to gas  vaporization • Gas to liquid  condensation • Gas to solid  deposition

23. LeChatelier’s Principle • When a system in equilibrium is stressed, it attains a new equilibrium which will minimize stress

24. Stresses • Addition of liquid • Removal of liquid • Addition of vapor • Removal of vapor • Decrease in volume • Increase in volume • Decrease in temp • Increase in temp

26. Equilibrium Vapor Pressure • The pressure exerted by a vapor in equilibrium with its corresponding liquid at a given temperature

27. Phase Diagrams • Triple point – the temperature and pressure at which all 3 phases can exist • Critical point – indicates critical pressure and temperature • Critical Temp: temp at which a substance cannot exist in the liquid state • Critical Pressure: the lowest pressure at which a substance can exist as a liquid at the critical temperature

29. Volatile vs. Non-volatile • Volatile liquids evaporate easily (i.e – lower temperatures)

30. 12-4: Water

31. Physical Properties of Water • Clear • Colorless • Odorless • Tasteless • Molar heat of fusion is 6.009 kJ/mol (amount of heat energy needed to melt one mole of water) • Molar heat of vaporization is 40.79 kJ/mol (amount of heat energy needed to vaporize one mole of water)