CHAPTER 12

A comparison of Liquids & Solids  Molecular speed   Molecular distance   Molecular “order”   Amount/Strength of Bonds  Solids are slowest s closest; g farthest s > l >g

LIQUIDS  Indefinite shape   Definite volume   Not very compressible   Fluid   Ability to diffuse  Takes shape of container Volume will change only slightly – with pressure or temp changes Can’t change volume easily; Particles are more closely packed together Particles can “flow” – can glide past one another Constant random particle motion

LIQUIDS  Surface Tension A force that tends to pull adjacent parts of a liquid’s surface TOGETHER & DOWNWARD, thus making the surface less penetrable by solid bodies

LIQUIDS  How many pennies can you fit into a cup full of water?  How many drops of water can you fit on the surface of a penny?  Can you float a paper clip? Use: Regular water Soap water Salt water

LIQUIDS  Ability to vaporize  Ability to solidify Vaporization; liq  gas; Two ways this can happen: BOILING, EVAPORATION Becoming a solid; liq  solids; Forces hold particles together in a solid

SOLIDS  Can be: Crystalline Crystalline Amorphous Amorphous Consists of crystals Particles are arranged in an ORDERLY, GEOMETRIC, REPEATING pattern Particles are arranged RANDOMLY Ex – glass, plastic micBonding/BondingMechanisms/Difference/Difference.htm

SOLIDS  Definite shape   Definite volume   NOT fluid   Not compressible  Shape does not change; Forces hold particles together Volume does not change; Particles packed very close together Does not flow; Particles held in fixed positions Very little empty space between particles

SOLIDS  Extremely SLOW diffusion   High density   Ability to melt  Strong attractive forces – don’t mix on own Particles packed very close – high mass, low volume solid  liq

CRYSTALLINE SOLIDS  Ionic Crystalline Solids Transfer of electrons, (metal + nonmetal) Transfer of electrons, (metal + nonmetal) Crystal Lattice Crystal Lattice Overall structure of an ionic compoundOverall structure of an ionic compound Unit Cell Unit Cell Smallest portion of a crystal lattice that reveals the 3D patternSmallest portion of a crystal lattice that reveals the 3D pattern There are 7 different shapesThere are 7 different shapes /overview/ch10.htmhttp:// /overview/ch10.htmhttp:// /overview/ch10.htmhttp:// /overview/ch10.htm

Crystalline Solids  Examples Cubic Cubic 90° angles90° angles L=w=hL=w=h Tetragonal Tetragonal 90° angles90° angles 2 dimensions equal; l=w ≠h2 dimensions equal; l=w ≠h Orthorhombic Orthorhombic 90° angles90° angles No dimensions equal; l≠w≠hNo dimensions equal; l≠w≠h

Crystalline Solids  Covalent Networks Single atoms covalently bonded to its nearest neighboring atom Single atoms covalently bonded to its nearest neighboring atom Examples: Examples:

Diamond  Hard  Strong  Interlocking tetrahedrals

Graphite  Sheets  Weak intermolecular forces between sheets  Sheets glide past one another and allow a thin deposit of graphite as you write

Buckminsterfullerene: Buckyball  “Soccer ball”  32 faces – 20 hexagons and 12 pentagons Nanotubes – Reactions in Chemistry - Workshop 1 – Beginning – 4:00

Metallics  Positive ions of metals surrounded by electron sea  High electric conductivity due to the freedom of electrons to move

Covalent Molecular  Molecules held together by intermolecular forces (external bonds)  Low MP,  Example - ice

Amorphous Solid  Noncrystalline solids  NO regular pattern Particles arranged randomly Particles arranged randomly  Examples: Rubber, glass (read article!), plastic Rubber, glass (read article!), plastic

Changes of State  Equilibrium Two opposing changes occur at equal rates Two opposing changes occur at equal rates Evaporation in a closed container Eventually… Evaporation rate = condensation rate

LeChatlier’s Principle Add a stress (change in concentration, change in pressure, change in temperature) to a system and the system will work to relieve the stress Add a stress (change in concentration, change in pressure, change in temperature) to a system and the system will work to relieve the stress RULES – RULES – Shift away from an added substance, towards removed substance (Solids do not affect concentration!!)Shift away from an added substance, towards removed substance (Solids do not affect concentration!!) Treat energy as a reactant/product for changes in tempTreat energy as a reactant/product for changes in temp If decrease volume – shift towards side with fewer gas moleculesIf decrease volume – shift towards side with fewer gas molecules

LeChatlier’s Principle  Example: As 4 O 6 (s) + 6C(s) As 4 (g) + 6CO(g) As 4 O 6 (s) + 6C(s) As 4 (g) + 6CO(g) How would this shift if?How would this shift if? Add CO Add CO Remove As 4 O 6 Remove As 4 O 6 Remove As 4 Remove As 4 N 2 (g) + 3H 2 (g) 2NH 3 (g) N 2 (g) + 3H 2 (g) 2NH 3 (g) How would this shift if?How would this shift if? Decrease volume Decrease volume CaCO 3 (s) + energy CaO(s) + CO 2 (g) CaCO 3 (s) + energy CaO(s) + CO 2 (g) How would this shift if?How would this shift if? Increase temperature Increase temperature Decrease temperature Decrease temperature

LeChatlier’s Principle Video: 2 CrO 4 2- (aq) + 2 H+ (aq) Cr 2 O 7 2- (aq) + H 2 O (l)

Boiling  Conversion of a liquid to a vapor  VAPOR PRESSURE Amount of gas above the liquid surface Amount of gas above the liquid surface Boiling occurs when VP = P atm Boiling occurs when VP = P atm  If P atm low … Boiling occurs easier…low BP Boiling occurs easier…low BP Food takes longer to cook Food takes longer to cook  If P atm high… Boiling is difficult…high BP Boiling is difficult…high BP Food cooks faster Food cooks faster

Boiling  Normal Boiling Point Boiling point at standard atm pressure (1 atm, 760 mmHg, etc) Boiling point at standard atm pressure (1 atm, 760 mmHg, etc)

Melting/Freezing Normal MP/FP of water = 0°C (NOT affected by pressure changes!!) Solid  gas Some substance do this at room temperature Some substance do this at room temperature Example – dry ice (solid CO 2 )Example – dry ice (solid CO 2 ) Sublimation

Heating/Cooling Curves Plateaus occur because energy is changing the external bonds!

Phase Diagram  Water:

Phase Diagram  Carbon Dioxide

Phase Diagram  Triple Point All three states of matter exist simultaneously All three states of matter exist simultaneously (an alcohol)  Critical Point Last temp and pressure at which a liquid can exist Last temp and pressure at which a liquid can exist  Difference between phase diagram of water and carbon dioxide?

Water  Liquid water Has “clumps” ofHas “clumps” of 4-8 molecules per group  Solid water Forms hexagonal lattice (6 sides) with empty spacesForms hexagonal lattice (6 sides) with empty spaces Gives solid ice low density (large volume, small mass)Gives solid ice low density (large volume, small mass) Solid floats on liquid!!Solid floats on liquid!!