Chapter 12. Intermolecular Forces: Liquids, Solids, and Phase Changes

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1 Chapter 12 Intermolecular Forces: Liquids, Solids, and Phase Changes Intermolecular Forces: Liquids, Solids, and Phase Changes 12.1 An Overview of Physical States and Phase Changes 12.2 Quantitative Aspects of Phase Changes 12.3 Types of Intermolecular Forces 12.4 Properties of the Liquid State 12.5 The Uniqueness of Water OMIT 12.6 The Solid State: Structure, Properties, and Bonding 12.7 Advanced Materials Intermolecular forces are forces between molecules while intramolecular forces are forces within a molecule. Intermolecular forces explain many important physical properties of compounds on the planet. Boiling and Freezing Point Viscosity Intermolecular Force attractive forces between molecules Forces Between Molecules Forces Within A Molecule Intramolecular Force Ionic or covalent bonding forces within a molecule or ionic substance (i.e. internal chemical bonds). Surface Tension Wetting or Not Wetting capillary action Intermolecular forces play a critical role in life as we understand it. Intermolecular forces (hydrogen bonding) hold together the double helix of DNA. Polar heads in aqueous exterior Embedded Proteins Nonpolar tail Aquoues Interior

2 Paper is dried network of cellulose fibers held together by hydrogen bonds and Van der waals forces. ~0.7 mm entangled pulp fibers Fiber Dimensions: 10 nm to 10 mm A phase is a state of matter that is homogeneous, chemically uniform and has physically distinct properties (density, crystal structure, index of refraction). We recognize 4 states of matter: 1. Gas 2. Liquids 3. Solids 4. Plasma (hot ionized gas) SOLID LIQUID GAS ~0.7 mm Smook s andbook 1992 Phase Properties very high density not compressible low Kinetic energy small distance between molecules IMF large high density not compressible mid Kinetic energy molecules close but fluid IMF large low density high compressibility high Kinetic energy large distance between molecules no IMF Kinetic molecular theory states that the temperature of collection of particles (system) is proportional to the average kinetic energy of the collection. The phase of a substance shows unique and varying different properties. Property Gases Liquid Solids KE = Ek = 3 2 RT Molecular Mobility Expand to occupy container Assumes shape of container Fixed Shape molecules fixed Kinetic Energy Temperature The phase of a substance depends on the competition between KE, which keeps molecules far apart and moving, and IMF which keep molecules close together and condensed. Gas Liquid Density Very low density igh igh Compressibility igh Very Very low Notcompressible Diffusion high molecular speeds Molecule slide past one another flow Atoms and molecules are fixed Kinetic Energy igh Medium Low KE Temperature Vs Intermolecular Force Intermolecular Forces Few and small Many Many Think of the different phases as classes of possible molecular motion due to different kinetic energies (caused by temperature differences) and varying degrees of intermolecular forces. Δ < 0 DEPOSITION Δ > 0 SUBLIMATION Gas CONDENSATION EVAPORATION Δ > 0 Δ < 0 Enthalpy is just another word for heat (q) given off or absorbed by a system at constant pressure. Internal Energy =!E = qp P!V Solve for qp q P =! =!E P!V Chemists measure the enthalpies of many reactions, tabulate them in handbooks and give them specific names. MELTING Δ > 0 Solid FREEZING Δ < 0 Liquid

3 The latent heat of fusion and the latent heat of vaporization are measured enthalpies for a pure solid and liquid that tell us something about the IMF between molecules. Molar eat of Fusion (" fus ): The energy required to melt! vap one mole of solid (in kj).! fus Notice how IMF s are weaker in solidliquid transition (! fus) vs liquidgas transition (! vap) Molar eat of Vaporization (" vap ): The energy (in kj) required to vaporize one mole of liquid. Molar eat of Sublimation (" sub ): The energy (in kj) required to vaporize one mole of solid to gas. The differences in energy required to vaporize or melt a pure substance tells us something about the IMF s that try to keep these molecules together in the condensed phase. IMF s are greater in the liquid phase. More energy per mole needed to vaporize than to melt! Temperature C ere s the same curve now applying the conservation of energy (sum of the heats) q = s ice m ice Tq = m ice fus q = s 2O m 2O T eating solid ice to 0 C A Ice Phase transition Temperature does not change during a phase transition. B Ice Water mix C Melting solid ice to 0 C water Water eating water to boiling 100 C D q = m 2O vap Phase transition Temperature does not change during a phase transition. Water steam mix Boiling all water to steam 100 C q = s stm m stm T Steam eating steam past 100 C eat Added (kj/mole) E F We can graphically show the qualitative and quantitative aspects of a phase change by plotting the temperature of a substance vs heat (q) added to a substance. Temperature C eat Added (Joules) Temperature C ere s the same curve now applying the conservation of energy (sum of the heats) q = s ice m ice Tq = m ice fus q = s 2O m 2O T eating solid ice to 0 C A Ice Phase transition Temperature does not change during a phase transition. B Ice Water mix C Melting solid ice to 0 C water Water eating water to boiling 100 C D q = m 2O vap Phase transition Temperature does not change during a phase transition. Water steam mix Boiling all water to steam 100 C q = s stm m stm T Steam eating steam past 100 C eat Added (kj/mole) E F The specific heat (s) of a substance is the amount of heat (q) required to raise the temperature of one gram of the substance by one degree Celsius. The molar heat capacity of a substance is the amount of heat (q) required to raise the temperature of one mole of the substance by one degree Celsius. eat absorbed (Joules) specific heat capacity J/g C or J/mol K q = s m!t # of moles or grams Change in Temp: C or K

4 The specific heat (s) of a substance is the amount of heat (q) required to raise the temperature of one gram of the substance by one degree Celsius. (ow thermally sensitive a substance is to the addition of energy!) eat (q) absorbed or released: q = s m!t Calculate the amount of heat required to convert 500 grams of ice at 20.0 C to steam at 120. C. The specific heat capacities of water, ice and water vapor are 4.18, 2.06 and 1.84 J/g C respectively, and the latent heat of fusion and vaporization,!f and!v, are 6.02 and 40.7 kj/mol respectively. n q i = 0 i=1 sum the q s baby q = si mi!t qsolid=>liquid = # moles! fusion qliquid=>gas = # moles! vaporization for nonphase transitions for phase transitions Calculate the amount of heat required to convert 500 grams of ice at 20 C to steam at 120 C. The specific heat capacities of water, ice and water vapor are 4.18, 2.06 and 1.84 J/g C respectively, and the latent heat of fusion and vaporization,!f and!v, are 6.02 and 40.7 kj/mol respectively. Calculate the amount of heat required to convert 500 grams of ice at 20 C to steam at 120 C. The specific heat capacities of water, ice and water vapor are 4.18, 2.06 and 1.84 J/g C respectively, and the latent heat of fusion and vaporization,!f and!v, are 6.02 and 40.7 kj/mol respectively. 1. eat ice from 20 C to ice at 0 C = 500. g x 2.06 J/g C x 20 C 2. Melt ice at 0 C to water at 0 C = 500. g/(18 g/mol) x 6.02 kj/mol 3. eat water from 0 C to water at 100 C= 500. g x 4.18 J/g C x 100 C 4. Evap water at 100 C to vap at 100 C = 500. g/(18 g/mol) x 40.7 kj/mol 5. eat vap from 100 C to vap at 120 C = 500. g x 1.84 J/g C x 20 C 1. = 20.6 kj 2. = kj 3. = kj 4. = kj 5. = 18.4 kj Total = kj Dynamic chemical equilibrium is condition reached when the rate of evaporation and rate of condensation are equal (no net change). Equilibrium Dynamic equilibria also occurs with melting and sublimation and also in most chemical reactions. At the melting point a solid begins to change into a liquid as heat is added. As long no heat is added or removed melting (red arrows) and freezing (black arrows) occur at the same rate an the number of particles in the solid remains constant. Solid Liquid Time Molecules in liquid begin to vaporize Molecules vaporizing and condensing at such a rate that no net change in numbers occure aa bb Reactants Reaction Rate of the forward reaction = cc dd Products = Reaction Rate of Reverse reaction

5 In open containers molecules that have enough KE can overcome IMF s at the surface and evaporate into the atmosphere. Evaporation Liquid no equilibrium In closed containers, molecules vaporize and condense until there is no further change in concentration. The trapped molecules in the gas phase form a equilibrium vapor pressure above the liquid s surface. Vapor Pressure Liquid equilibrium The equilibrium vapor pressure is the pressure exerted by a vapor over its liquid phase (measured under vacuum) when a dynamic equilibrium exists between condensation and evaporation. Vapor Pressure The vapor pressure of a liquid is the partial pressure exerted by the liquid s vapor when it is in dynamic equilibrium with a liquid at a constant temperature. As T " vapor pressure " As a liquid s temperature increases, so does its KE. The number of molecules with enough energy to overcome IMF s increase allowing vaporization. KE = Ek = Kinetic Energy 3 2 RT Temperature The temperature at which the vapor pressure equals the external pressure over the liquid is the boiling point. The normal boiling point is the temperature at which a liquid boils when the external pressure is 1 atm. T1 T2 Evaporation Boiling T1 Molecules with enough speed to vaporize T2 > T1 Speed KE needed to overcome IMF in liquid phase Vapor Pressure (torr) The vapor pressure of a pure liquid depends on the IMF s between molecules. The stronger the attractive IMF forces in the liquid phase => the lower the vapor pressure => the less volatile the liquid it is. Shape of the curve is exponential Temperature ( C) 2 atm 1.00 atm.66 atm Which of the following has the highest vapor pressure at 1 atm? Which is the least volatile at 1 atm? If we plot ln (vapor pressure) vs 1/Temp we observe a linear relationship. Vapor pressure (torr) Vapor pressure plotted as a function of temperature Temperature C ln P ln (vapor pressure) plotted as a function of 1/Temp 1/T

6 The ClausiusClaperyron equation relates the vapor pressure (P) of a pure liquid to the liquid s temperature (T) and the liquids molar heat of vaporization (! vap ). Vapor Pressure (torr) of Some Liquids Vapor Pressure of Some Liquids ln P =!vap " 1% $ ' C R # T& slope =! vap /R y = m x b R = 8.31 J/K mol By taking measurements at two temps, we get: ln P eat of Vaporization, Boiling Pts of Liquids ln P 2 =!vap # 1 " 1 & % ( P R T 1 $ 2 T 1 ' 1/T Vapor pressure of pure eto is 115 torr at 34.9 C. If!vap = 40.5 kj/mol calculate the temperature when the vapor pressure of eto is 760 torr. R is the gas constant given at J/mol K Vapor pressure of pure eto is 115 torr at 34.9 C. If!vap = 40.5 kj/mol calculate the temperature when the vapor pressure of eto is 760 torr. R is the gas constant given at J/mol K!vap =40.5 kj/mol P1=115 torr P2=760 torr T1= = 308.0K ln P 2 =!vap # 1 " 1 & % ( P 1 R $ T 2 T 1 ' ln 760 torr 115 torr = 40.5 x10 3 J/mol J/mol*K 1 1 T 2 308K T 2 = 350K = 77 C The following diagram shows a closeup view of part of the vaporpressure curves for a solvent (red curve) and a solution of the solvent with a second liquid (green curve). Which solvent is more volatile? The following diagram shows a closeup view of part of the vaporpressure curves for a solvent (red curve) and a solution of the solvent with a second liquid (green curve). Which solvent is more volatile? The more volatile solvent will have a higher vapor pressure (more gas molecules in the gas phase above its liquid). The green solvent has a higher vapor pressure at all temperatures. It has weaker IMF s.

7 Pressure (Atm) A phase diagram summarizes the conditions at which a substance exists as a solid, liquid, or gas phase of matter Freezing Point A Solid Melting Freezing Sublimation Deposition Liquid Evaporation Condensation Gas Supercritical Fluid D AB is the solidliquid (sublimation) curve for ice; BD the vapor pressure curve for watersteam; BC the solidliquid (melting point line); point B the triple point point D labels the critical point. 374 Gas Critical Point Normal Boiling Point Triple Point A phase diagram summarizes the conditions at which a substance exists as a solid, liquid, or gas phase of matter. Line AB is the vaporpressure curve for solidvapor (sublimation curve); BD the vapor pressure curve for liquidvapor water; BC the melting point line (notice how it has a negative slope = solid is lower density); point B the triple point: only point when three phases are in equilibrium; point D is the critical pointthe temperature at which no pressure can liquefy a gas (new phase of matter). Terminology in a Phase Diagram The triple point is the single P,T point at which all three phases are in equilibrium with one another. The critical temperature (T c ) is the temperature above which the gas cannot be made to liquefy, no matter how great the applied pressure. Water is one of the few substances on earth for which the liquid phase is more dense than its solid phase. We see this in its phase diagram as the negative slope of the solidliquid line (higher pressure decreases the melting point) more pressure at a fixed temperature leads to a liquid not a solid Water more pressure at a fixed temperature leads to a solid not a liquid CO2 The critical pressure (P c ) is the minimum pressure that must be applied to bring about liquefaction at the critical temperature. The normal boiling point is the temperature at which the vapor pressure of a liquid equals 1 atm. The normal freezing point is the temperature at which the liquid is in equilibrium with its solids phase at 1 atm. Pressure (torr) K Generally speaking, which phase of a substance should have the highest density (mass/volume)? Name a compound that does not follow this trend? A B D C Temp C From Line E to G what is occurring? From Line J to E what is occurring? Between what two points is the vapor pressure curve. Which two points define the melting point curve What is the normal boiling point of this substance? What is the triple point of this substance? GAS LIQUID SOLID

8 Electronegativity is an element s inherent property to draw electrons to itself when chemically bonded to another atom in a molecule. Lookout for bonds having: F, O, Cl, N, Br, I F is the most electronegative element Connecting Dots: large electronegativity differences in a bond => polar molecules => large dipole moments => gives rise to large IMF => decreased vapor pressure => increased boiling and melting points, higher viscosity, higher surface tension.!!!! Polar with net dipole moment Polar with!! net dipole moment!!!!! Polar with net dipole moment nonpolar with no net dipole moment Cs the least nonpolar with no net dipole moment We must consider molecular and electron geometry to determine a molecule is polar! 3 EG 4 EG 2 EG Intermolecular forces result from electrostatic forces between molecules. There are 4types of IMF s. 1. Iondipole: occur between neighboring an ion solution and a polar molecule (dipole) also in solution. Na 2. Dipoledipole: occurs between neutral polar molecules (they can be different or the same interacting molecules). 5 EG 6 EG 3. Induceddipoles: occur when a ion or a Ion or Dipole Induced Dipole dipole induces a spontaneous dipole in a neutral polarizable molecule. 4. London Dispersion Forces are attractive IMF s that occur between all molecules. Spontaneous dipoles are formed randomly or induced by other charged species in neutral polarizable molecules. Summary of 4 types of IMF s Type of Interaction Ion Dipole Dipole Energy (kj/mol) ighest an ion interacts with a polar molecule (dipole). two polar molecules (dipoles) interact electrostatically. Induced Dipole Dipole ion or a dipole induces a dipole in a polarizable nonpolar molecule Lowest Intermolecular forces arise from electrostatic forces and depend on distance between molecules. Coulomb s Law: The electric force acting on a point charge q1 as a result of the presence of a second point charge q2 some r meters away is given by: units of coulombs k q1 q2 F= r2 r units of meters k depends on medium (kair = 9.0 x 109 N m2/c2) 215 also called London Dispersion Forces occurs between nonpolar molecules via polarizability Induced Dipole Induced Dipole Interaction Dipole Ion Strength Because Energy = Force x Distance Energy of Attraction is: E= k q1 q2 r If we can predict charge separation or polarity in molecules we can identify IMF s in play for that molecule.

9 Comparing the strengths of Intermolecular Forces 1. Iondipole forces are attractive forces between an ion in solution and a neighboring polar molecule. Force London Forces Dipole Dipole ydrogen Bonding Strength Energy Distance Interactions 110 kj/mole 1/r 6 Allmolecules 340 kj/mole 1/r 3 Polar molecules 1040 kj/mole 1/r 3 O N F IonDipole 1050 kj/mole 1/r 2 IonsPolar molecules end of dipole attracted to ions Molecules with a dipole moment in solution end of dipole attracted to ions IonIon >>200 kj/mole 1/r CationAnion An anion in solution A cation in solution 2. DipoleDipole intermolecular forces are attractive forces that occur between polar molecules (same or not the same). Nonpolar Molecule (no dipole moment) Polar Molecule (dipole moment) 3. ydrogen bonding is a special case of dipoledipole intermolecular force that occurs between a hydrogen atom and an unshared pair of electrons in a polar N, O, or F bond. VS Notice the very large difference in boiling point caused by IMF s present in acetone (lacking in butane)! Water is a highly polar molecule due to oxygen inherent ability to attract electrons more so than hydrogen. The boiling points of covalent binary hydrides increase with increasing molecular mass down a Group but the hydrides of N3, 2O and F have abnormally high BP because of hydrogen bonding. There is more electron density near the oxygen atom and less around the hydrogen (arrows). This polarity property gives water its dissolving properties of other polar substances. Temperature C ? Increased London Forces Period

10 As dipole moments increase in polar substances of the same mass, IMF s increase as do boiling points (lower vapor pressure) and melting points. 4. London Dispersion Forces (or Van deer waal forces) are attractive intermolecular forces when temporary dipoles are formed due to random electron motions in all polarizable molecules. Two nonpolar polarizable molecules Nonpolar Polar spontaneous movement of electrons forming an instantaneous dipole moment Very polar InducedDipole Moment and IMF between molecules Polarizability is the ease with which an electron distribution (cloud) in the atom or molecule can be distorted by an outside ion or dipole. nonpolar molecule (electron cloud) spontaneous induced dipole that depends on polarizability of substance London Dispersion Force induced dipole dispersion All molecules have at least this IMF Polarizability and London dispersion trends mirror atomic size trends in the periodic table. Size and polarizability increases down a group Polarizability increases right to left (bigger size more distortable. POLARIZABILITY Polarizability increases with molar mass (# e) of a molecule Cations are less polarizable than their parent atom because they are smaller and more compact. Anions are more polarizable than their parent atom because they are larger. London dispersion forces increase with size and polarizability. Increasing Size/ Polarizability Cations are less polarizable than their parent ground state atoms while anions have a larger polarizability than their ground state atoms. Rank the following in order of increasing polarizability: Increasing Size & Polarizability Na vs Na Br vs Br Mg 2 vs Al Cl vs Cl Rank the following in order of increasing polarizability: Na > Na Br < Br Mg 2 < Al Cl > Cl

11 Larger unbranched molecules are more polarizable than compact branched molecules. neopentane bp=10 o C tetrahedral normal pentane bp=36 o C extended structure Larger polarizability in unbranched molecules explains boiling and melting points trends in isomers. Key Generalizations Good To Know About IMF s 1. IonIon > IonDipole > DipoleDipole > London Forces 2. For polar molecules of approximately the same mass and shape and volume (i.e. polarizability the same), dipoledipole forces dictate the difference in physical properties. 3. ydrogen bonding (special dipoledipole) occurs with specific polar bonds: F, O, N C=O and an unshared pair of electrons on a nearby electronegative atom usually F, O, or N. 4. For nonpolar molecules of the same molecular mass, longer less compact molecules are more polarizable than compact molecules and show London forces. 5. For nonpolar molecules of widely varying molecular mass, those with more mass are typically more polarizable and experience greater London dispersion forces and exhibit higher boiling points and melting points. Flowchart for classifying intermolecular forces! Arrange the following substances in order of increasing boiling points. C 2 6, N 3, Ar, NaCl Ar < C 2 6 < N 3 < NaCl nonpolar nonpolar polar ionic London London dipoledipole bonding ionion! Arrange the following substances in order of increasing boiling points. C 2 6, N 3, Ar, NaCl, As 3 Which of the following substances exhibits bonding? For those that do, draw two molecules of the substance with the bonds between them. (a) C 2 6 (b) C 3 O (c) C 3 C N 2 O PLAN: Find molecules in which is bonded to N, O or F. Draw bonds in the format B: A.

12 Which of the following substances exhibits bonding? For those that do, draw two molecules of the substance with the bonds between them. Which substances experience dipoledipole intermolecular forces? SiF4,CBr3, CO2, SO2 (a) C 2 6 O (b) C 3 O (c) C 3 C N 2 PLAN: Find molecules in which is bonded to N, O or F. Draw bonds in the format B: A. SOLUTION: (b) (a) C 2 6 has no bonding sites. C O (c) O C 3 C N O C N C 3 C O O C 3 C N N C 3 C O Which substances experience dipoledipole intermolecular forces? SiF4,CO2, SO2, CBr3, Arrange the following nonpolar molecules in order of increasing melting point. SiF4, geometry tetrahedral, SiF bonds are polar, but no molecular dipole; bond dipoles cancel. No dipoledipole interactions. SiF4, CS2, CI4, GeCl4 CO2, linear geometry, CO bonds are polar but symmetry cancels net diple, but no molecular dipole; bond dipoles cancel and no dipole IMF s SO2, bent geometry, SO bonds are polar and do not cancel. Sulfur lone pair dipole only partially offsets net bond dipole. as dipoledipole forces CBr3, tetrahedral geometry, C and CCl bonds are polar and do not cancel SO2 and CCl3 experience dipoledipole intermolecular forces. Arrange the following nonpolar molecules in order of increasing melting point. SiF4, CS2, CI4, GeCl4 Solution. None of these molecules poses a net dipole moment. Only dispersion forces exist and these are expected to increase with increasing molecular mass (more polarizable as a molecule gets larger). The molar masses of these substances follow: Substance Molar Mass CS SiF CI GeCl The intermolecular forces, and the melting points, should increase in the following order: CS2 < SiF4 < GeCl4 < CI4 The experimentally determined melting points are 110.8, 90, 49.5, and 171 o C, respectively. For each pair of substances, identify the dominant intermolecular forces in each substance, and select the substance with the higher boiling point. (a) MgCl 2 or PCl 3 (b) C 3 N 2 or C 3 F (c) C 3 O or C 3 C 2 O (d) exane (C 3 C 2 C 2 C 2 C 2 C 3 ) or 2,2dimethylbutane PLAN: C 3 C 3 CC 2 C 3 C 3 Bonding forces are stronger than nonbonding(intermolecular) forces. ydrogen bonding is a strong type of dipoledipole force. Dispersion forces are decisive when the difference is molar mass or molecular shape.

13 For each pair of substances, identify the dominant intermolecular forces in each substance, and select the substance with the higher boiling point. SOLUTION: (a) Mg 2 and Cl are held together by ionic bonds while PCl 3 is covalently bonded and the molecules are held together by dipoledipole interactions. Ionic bonds are stronger than dipole interactions and so MgCl 2 has the higher boiling point. (b) C 3 N 2 and C 3 F are both covalent compounds and have bonds which are polar. The dipole in C 3 N 2 can bond while that in C 3 F cannot. Therefore C 3 N 2 has the stronger interactions and the higher boiling point. (c) Both C 3 O and C 3 C 2 O can bond but C 3 C 2 O has more C for more dispersion force interaction. Therefore C 3 C 2 O has the higher boiling point. (d) exane and 2,2dimethylbutane are both nonpolar with only dispersion forces to hold the molecules together. exane has the larger surface area, thereby the greater dispersion forces and the higher boiling point. Any Name questions the types of on intermolecular homework forces from in Chapter the following 11? compounds. C3C2C2C3 C3O C3CON2 C3COO C3C2C2C2O C3C2COC3 In which substances would hydrogen bonding forces occur between molecules? In which substances would hydrogen bonding forces occur between molecules? C26, CCl3, C3C2O, NO3, P3 C26, CCl3, C3C2O, NO3, P3 Solution. ydrogen is bonded to one of the very electronegative atoms in C3C2O and NO3. ydrogen bonding should occur in both of these substances. Water Is A Unique Substance Ice is less dense than water great solvent due to high polarity and hydrogen bonding ability exceptional high specific heat capacity and "vaporization high surface tension and capillarity large density differences of liquid and solid states Density (g/cm 3 ) Density of Water Maximum Density 4 0 C Temperature C Water Is Wild and Unique and Taken For Granted igh bonding = high cohesive forces responsible for the transport of water in roots and xylem of trees and plants. Basepairing in doublestranded DNA eat capacity, high heat of vaporization, inverted density of water and ice.

14 Three common physical properties of liquids that depend on the magnitude of IMF s include surface tension, capillarity and viscosity. Surface tension is the amount of energy required to stretch or increase the surface area of a liquid by a unit area (J/m 2 ). molecules at the surface feel a net force downward surface tension Viscosity capillarity Scientists say that the leaf has a low surface energy as water will not spread out (it takes energy to spread the water out) molecules in the interior experience equal force in 3D Surface Tension of Some Liquids The physical properties of a pure liquid are related to its intermolecular forces. Substance Formula Surface Tension (J/m 2 ) at 20 0 C Major IMF s diethyl ether C 3 C 2 OC 2 C 3 1.7x10 2 dipoledipole; dispersion ethanol C 3 C 2 O 2.3x10 2 bonding butanol C 3 C 2 C 2 C 2 O 2.5x10 2 bonding; dispersion water 2 O 7.3x10 2 bonding mercury g 48x10 2 metallic bonding Capillary effect occurs when the adhesive IMFʼs between a liquid and a substance are stronger than the cohesive IMFʼs inside the liquid. Cohesion is the intermolecular attraction between like molecules. Adhesion is an attraction between unlike molecules Water will rise to different heights in tubes depending on the diameter of the capillary. Can you surmise why and how? Cohesion Adhesion SiO glass Capillary rise implies that the: Adhesive forces > cohesive forces Capillary fall implies that the: Cohesive forces > adhesive forces

15 Water will rise to different heights depending on the diameter of the capillary. Why? Viscosity is the measure of a liquid s resistance to flow relative to one another, and is thus related to the intermolecular forces.! Oil for your car is bought based on this property: 10W30 or 5W30 describes the viscosity of the oil at high and low temperatures (W means winter dudes higher the number the more viscous). In general, viscosity decreases as temperature increases and visa versa. Copyright The McGrawill Companies, Inc. Permission required for reproduction or display. Figure The viscosity of a polymer in solution. 12