Liquids & Solids

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

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

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

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

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)

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

Crystalline Solids

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

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

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

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

Amorphous solids “without shape” Plastics and glass

Changes of State

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

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

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

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

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

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

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

12-4: Water

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