Week 13 book notes
Week 13 book notes Chem 141
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This 4 page Class Notes was uploaded by Cassidy Zirko on Tuesday November 24, 2015. The Class Notes belongs to Chem 141 at University of Montana taught by Mark Cracolice (P) in Fall 2015. Since its upload, it has received 7 views. For similar materials see College Chemistry 1 in Chemistry at University of Montana.
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Date Created: 11/24/15
Prof Cracolice Chem 141 Week 13 Notes Chapter 34 What are the Characteristics of Phase Equilibrium 112315 341 What is the Relationship Between a Liquid and Its Vapor Kinetic Energy Distribution Curve range of kinetic energies at a certain temperature Kinetic energy plotted horizontally fractionpercentage of sample plotted vertically Evaporating only occurs with molecules on the surface of the liquid Temperature and surface tension determines rate at which particulates of the liquid evaporates Equilibrium rates of change in opposite directions are equal Dynamic equilibrium molecules constantly switching between liquid and vapor phases Equilibrium Vapor Pressure the partial pressure exerted by a vapor in equilibrium with its liquid phase at a given temperature Reversible changes reversible reactions changes that can occur in either direction symbolized with double arrows Increase number of molecules with enough energy to evaporate is responsible for high vapor pressure at high temperatures Why do Liquids Boil O Heated in an open container I bubbles begin to form 0 Boiling vapor bubbles from throughout the liquid and rise to the surface and burst 0 Boiling point temperature at which vapor pressure of a liquid is equal to the pressure above its surface 0 Normal boiling point boiling point at 1 atm 0 Boiling point depends on pressure that is above the surface of the liquid 0 Pressure reduced I temperature of boiling point lowers because vapor pressure needs less heat to equal the pressure around the liquid 0 Raising boiling point I increase pressure Why is Water Different 0 Water is special 0 Electrons form bond between hydrogen and oxygen and are drawn towards oxygen forming two very polar bonds As hydrogen bonding I super important to water characteristics Has high surface tension and heat of vaporization Viscous in comparison dissolves many gases liquids and solids Ice oats on liquid water Most substances expand become less dense when heated 0 Most substances contract become more dense when cooled 00000 342 What Affects the Stability of Physical States of a Pure Substance Prof Cracolice Chem 141 Week 13 Notes Phase Diagram plotting pressure and temperatures at which a substance undergoes a phase change Solid lines signify that two or more phases exist along that line For water there is a negative slope between the liquid and solid phase because as the external pressure increases the freezing point decreases Sublimation describes transition between solid state and vapor state without a liquid in between Deposition transition between vapor and solid phase with no liquid phase in between Triple point all three phases exist at a specific temperature and pressure Supercritical fluid at a specific temperature and pressure phase are no longer distinctly seen Critical point pressure and temperature where liquid vapor equilibrium doesn t matter essentially a liquid and a gas at the same time Dry ice solid C02 sublimes at normal pressure very good for frozen transportation Melting point increased with increasing pressure Chapter 35 What are the Characteristics of the Solid State 113015 351 What Structures Characterize Solids Classified by macroscopic properties Creates differences at particulate level Crystalline solid solid who particles are arranged in a geometric pattern that repeats its self over and over again 0 Each particle is in a set specific location Amorphous solid no long range ordering of particles in the solid pattern does not repeat Intermediate between a solid and a liquid Not rigidly fixed Polycrystalline solid intermediate in particulate organization falling between disordered amorphous solids and crystalline solids randomly arranged Crystalline solids have physical properties that identify them What Properties Characterize Crystalline Solids O Ionic Crystals oppositely charged ions held together by strong electrostatic forces I Ex NaF C3CO3 or AgCl I High melting and water soluble I Low electrical conductivities I Ions more around when melted or dissolved 0 Molecular crystals Prof Cracolice Chem 141 Week 13 Notes I EX 12 ICl I Soft low melting point and insoluble in H20 I Are nonconductors when pure I Solid heat to a liquid I molecules rearrange into long chains and substances change macroscopic characteristics 0 Covalent Network Solids I EX diamonds quartz SiOz I Atoms covalently bonded to each other I No small molecules I High melting points I Almost always insoluble in H20 I Poor conductors of electricity 0 Metallic Crystals I EX Al I Crystal of positive ions through valance electrons more freely I Electron sea model of metal crystal I Positively charged ions form backbone of crystal I Electrons are not tied down to any particular ion I Some are amorphous at the macroscopic level 352 How do Chemists Study the Solid State 0 X rays travel through structural compounds 0 Xray crystallography chemists hypothesized that the particulate level reason fro the macroscopic regularity in the arrangement of particles 0 Crystalline solid pattern observed repeated over and over again 0 Unit cell smallest number of particles that can be identified that repeat to make up the overall crystal structure 0 Contents of unit cell have to be in a stoichiometric ration 0 Unit cell has same stoichiometric ration as particles in the sample 0 Cubic simplest of unit cell because it has equal lengths of sides and 90 degree internal angles 0 Three types of cubic structures 0 Each phase has 2 cubes 0 Each edge is a part of 4 cubes 0 Each corner is a part of 8 cubes 0 Body diagonal 4 time the length of an atom 41 Zedge length Prof Cracolice Chem 141 Week 13 Notes From edge length you can nd atomic radius 3l r 4 r radius FD2 l 2 BDZ FD face diagonal BD body diagonal 3 121 volume being used from a given density 353 Why do Metal Atoms Attach to One Another Most metals have 1 2 or 3 valance electrons Electrons held loosely to form cations Valance electrons cant be transferred to p orbital in nonmetal Positively charged ions resulting from loss of outer most s and p orbitals valance electrons existing in a sea of electrons Metallic Bond attractive forces between positively charged metal ions and regular charged valance electrons among them Covalent bonds between bonding electrons are localized Electrons in metallic bonds are delocalized because electrons cant stay near any single atom or pair Electrical current made up of moving electrons Metals bend instead of break because electrons rearrange themselves Alloy solid mixture of 2 or more elements that have macroscopic metallic properties
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