States of Matter Solids Liquids Gases 1
Solid vs. Liquid vs. Gas Depends on only two things: What? Attractions Kinetic between particles vs Energy of particles 2
Intermolecular Forces (Molecular Attractions) Molecules are attracted to each other by intermolecular forces. 3
Intermolecular Forces (Molecular Attractions) are what stick molecules together not bonds within a molecule are responsible for the solid and liquid states for molecules 4
3 Types: Intermolecular Forces (Molecular Attractions) Dipole-dipole force (dipole force) Dispersion force van der Waals forces Hydrogen bond force (a special dipole force) 5
1. Dipole-Dipole Force Electrostatic attraction of polar molecules, e.g HF and H 2 O. 6
Dipole-Dipole Buret with water charged rod (+) (-) (-) 7
Review: Polar Molecules A molecule with only two atoms is polar if the atoms have different electronegativities (>0.3). H-Cl polar Br-Br nonpolar 8
Review: Polar Molecules If more than 2 atoms in molecule: Draw dot structure If outside atoms are the same and central atom has no lone pair electrons, the molecule is nonpolar. 9
Are These Polar (do they have a dipole force)? CH 4 CH 3 Cl CO 2 SO 2 NH 3 NaCl 10
2. Dispersion Force All molecules have temporary polarity due to the random motion of the electrons around the nucleus. e- 11
2. Dispersion Force Attractive force resulting from the temporary polarity. + - + - Responsible for condensation of nonpolar gases Is stronger the larger the molecule (molar mass) 12
The States of Halogens All are nonpolar and have only dispersion forces. At room temperature: F 2 and Cl 2 :gases Br 2 : liquid. I 2 : solid. Increased molar mass so larger dispersion force 13
3. Hydrogen Bond Force A strong dipole-dipole attraction between molecules when hydrogen is bonded to N, O, or F F H H-bond force F H Why? d- d+ strong d- d+ strong 14
Hydrogen Bond H H H O H O electronegative F, O, or N atom H-bond from H to lone pair on O H atom on different molecule 15
Strength of Molecular Attractions 1. Dispersion Force (weakest unless molecule is large) 2. Dipole Force 3. H-Bond Force (strongest) 16
Name the Type of Molecular Attractions CH 4 (nonpolar) CH 3 Cl (polar) CO 2 (nonpolar) SO 2 (polar) NH 3 (polar) 17
Gases (KE >> attractions) Kinetic Molecular Theory 4 statements of KMT 18
Gases: KMT 1.Gas particles (atoms or molecules) are: Hard spheres Insignificant volume (compared to container) Far apart 19
Gases: KMT 2. Gas particles are in constant motion Random motion Straight line paths until collision Fill container 20
Gases: KMT 3. Gas particles have no intermolecular attractive forces between them. (not 100% true!) 21
Gases: KMT 4. Collisions are perfectly elastic no energy lost during collisions 22
Gas Mostly Empty Space Compare volumes in liters of: 1 mole water vapor (gas) 22.4 L vs. 1 mole liquid water 0.018 L Gas is >1000 times volume of liquid 23
Gas Speed Speed of O 2 at 20 o C is ~1660 km/hr. WOW!!! Why don t you smell perfume as soon as someone enters a room? 24
One the molecular level, what keeps the walls of a balloon pushed out? 25
Gas Pressure Pressure = force /area Gas molecules exert pressure on the walls of a container due to collisions. More molecules more pressure 26
Vacuum If there are no gas molecules, pressure is zero. 27
What Will Happen? water plastic sheet 28
Atmospheric Pressure Collision of air molecules with objects results in atm. pressure. 1.00 atm = ave. pressure at sea level 29
Atmospheric Pressure Is pressure higher or lower than 1 atm on top of Mt. Everest? 30
Measuring Pressure Vacuum 760 mm Hg atm P 31
Measuring Pressure 1 atm = 760 mm Hg = 101.3 kpa What is pressure in atm. and kpa during a hurricane if P = 720 mm Hg? (Table A) 32
Gas Temperature What happens when a gas is heated? Molecules speed up Average kinetic energy (energy of motion) increases. Temperature (K) increases 33
% molecules Kinetic Energy Distribution 100% NO!!! low T (K) high T (K) kinetic energy 34
Liquids A condensed state of matter. 35
Liquids similar Kinetic Energy of particles vs Attractions between particles 36
Molecules in Liquid in constant motion not much affected by pressure touching held together by intermolecular forces can glide past each other (flow) 37
Evaporation What happens to a glass of water left overnight? How can this happen below the boiling point? 38
% molecules Evaporation Energy to break intermolecular forces kinetic energy 39
Evaporation After some liquid evaporates, the remaining liquid is cooler. Why? 40
Evaporation in Closed Container Vapor pressure: Pressure due to evap. gas in closed container. open closed Depends on 2 things Attractions between particles vs Kinetic Energy of particles 41
Dynamic Equilibrium (closed container) Liquid evaporation condensation At equilibrium: Vapor (gas) rate evap. = rate cond. 42
Vapor Pressure As T increases, vapor pressure increases (more KE) 43
Table H: Vapor Pressure VP depends only on: substance temperature 44
Vapor Pressure Using Regents Table H: What is VP of ethanol at 60 o C? At what T does VP of water equal 50 kpa? Which substance has greater molecular attractions: ethanol or water? 45
Boiling Point (BP) normal boiling point (BP at 1 atm.) The temperature at which vapor pressure equals external pressure. 46
Boiling Add heat energy to overcome intermolecular forces. (T doesn t change!) How do you know when something is boiling? What s in the bubble? What s P in bubble? 47
Table H is also BP vs. Pressure! What is Boiling Point of H 2 O: in Endwell where P = 1.0 atm? in Denver where P = 86 kpa? on Mt. Everest where P = 35 kpa? 48
Boiling Point Would it take longer or shorter time to boil at egg in Denver or in Endwell? 49
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Solids Particles arranged in regular, repeating pattern called crystal lattice. 51
Comparison of K.E. to Molecular Attractions Gas: KE >> I.M. forces Liquid: KE ~ I.M. forces Solids: KE << I.M. forces (only vibrations are possible) 52
Solid Melting melting freezing Ionic compounds: high M.P. NaCl: 801 o C Break ionic bond Liquid Na + Cl - Molecular compounds: low M.P. HCl: -112 o C Break IM force HCl HCl 53
Allotropes Different forms of the same state of an element or compound. Example: carbon diamond graphite bucky-ball Bonded differently. 54
Other examples: Allotropes O 2 and O 3 Sulfur Red & white phosphorous 55
Amorphous Solids Solids with no crystal structure Examples: plastic asphalt glass 56
Network Solids All particles of the solid are interconnected by a network of covalent bonds (not IM forces). v. high melting point Example: diamond 57
Pressure (atm) Phase Diagram for H 2 O Normal M.P. Normal B.P. 1 solid liquid vapor Triple point 0 100 Temperature ( o C) 58
Sublimation Substance passes from solid directly to vapor. See phase diagram below Triple Point. examples: dry ice (CO 2 ) iodine (I 2 ) (demo) 59
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Lab 12 Analysis CuCl 2 + Fe Cu + FeCl 2 vs. 3CuCl 2 + 2Fe 3Cu + 2FeCl 3 DATA TABLE Mass empty dry beaker Mass iron nails (before rxn) Mass iron nails (after rxn) Mass beaker & dry product 61
Warm-up What is an intermolecular force? List the three types of IM forces. 62
Warm-up What is an intermolecular force? List the three types of IM forces. What types of IM forces hold SO 3 molecules together in the liquid state? 63
Warm-up List the three types of molecular attractions. What causes the dispersion force? Which molecules have this force? 64
Warm-up Predict the shape of PCl 3. Is it polar? What forces hold molecules of PCl 3 together? What are the 4 assumptions of KMT? 65
Warm-up Predict the shape of SCl 2. Is it polar? What forces hold molecules of SCl 2 together in the liquid state? What is meant by kinetic energy distribution? What is pressure? What is vapor pressure? What is VP of H 2 O at 80 o C? At 100 o C? 66
Warm-up Predict the shape of SCl 2.Is it polar? What forces hold molecules of SCl 2 together in the liquid state? What is pressure? Use KMT to explain why a balloon gets smaller when cold. 67
Warm-up What is STP? What molecular attractions hold ammonia molecules (NH 3 ) together? What temp. will water boil at if P = 620 mm Hg? How can liquid water in underground geysers be hotter than 100 o C? What is meant by kinetic energy distribution? 68
Warm-up What is STP? What molecular attractions hold ammonia molecules (NH 3 ) together? Define vapor pressure What temp. will water boil at if P = 520 mm Hg? What is meant by kinetic energy distribution? 69
Table H: Vapor Pressure 70