Solids, Liquids, And Gases
Chapter 10 Liquids and SolidsGases vs. Liquids and Solids In gases, the particles in the sample are widelyseparated, because the attractive forces between theparticles are very weak. In liquids, there are strong intermolecular forcesbetween the particles, which hold them in closecontact, while still letting them slip and slide overone another. In solids, the intermolecular forces are so strong thatthe particles are held rigidly in place.Chapter 10Liquids and SolidsChapter Objectives: Learn the differences between the solid, liquid, and gas state,and how the polarity of molecules influences those states. Learn the different types of intermolecular forces betweenmolecules. Learn about the energy changes that accompany phasechanges, and how to read phase diagrams.Mr. Kevin A. BoudreauxAngelo State UniversityCHEM 1311 General ChemistryChemistry 2e (Flowers, Theopold, Langley, Robinson; openstax, 2nd ed, 2019)www.angelo.edu/faculty/kboudrea2The Physical States of Matter Solids– have strong intermolecular forces.– have high densities in comparison to gases.– are rigid (have a definite shape) andincompressible (have a definite volume).– may be crystalline (ordered) [e.g. table salt] oramorphous (disordered) [e.g., plastics].Solids, Liquids,and Gases3The Physical States of Matter4The Physical States of Matter Liquids– have moderate intermolecular forces.– have high densities in comparison to gases.– are fluid (they flow, and have an indefinite shape)and incompressible (have a definite volume); theyconform to the shape of their containers (theyform surfaces). Gases– have weak intermolecular forces.– have low densities– are fluid and compressible; they have no definiteshape or volume, and conform to the containershape, but fill the entire volume (i.e., they do notform surfaces).56
Chapter 10 Liquids and SolidsThe Phases of WaterPhase Changes A solid can be converted into a liquid by heating,and to a gas by heating or reducing the pressure:Propane (C3H8) is stored in tanks atpressures above 2.7 atm, which turns it into aliquid. When the valve is opened, some ofthe propane evaporates into the gas phase.78Ion-Ion InteractionsIntermolecularForces9 Ionic compounds in general are solids at roomtemperature, with relatively high melting points (e.g.NaCl 801ºC, KClO3 356ºC, MgCl2 714 º C,Al2O3 2072ºC, MgO 2852ºC) From Coulomb’s Law, the product of the charges Q1and Q2 in the numerator is always negative— saltsare always more stable than the isolated cations andanions.– The distance d for ionic compounds is the sum ofthe ionic radii. Thus, some trends in meltingpoints can be predicted from trends in ion radius.– NaBr has a lower melting point (747ºC) thanNaCl; NaI is even lower (661ºC)1 Q1 Q2E Coulomb' s Law4πε 0dIntramolecular and Intermolecular ForcesIntramolecular and Intermolecular Forces Intramolecular forces operate within each molecule,influencing the chemical properties of the substance(i.e., covalent bonds). To break an O—H single bond in a water molecule,the water must be heated to thousands of degrees C;to completely overcome the intermolecular forces,all you have to do is boil it — 100ºC.– These are the forces that hold the atoms in a moleculetogether. They are very strong forces which result fromlarge charges (on protons and electrons) interacting oververy short distances.10 Intermolecular forces (van der Waals forces)operate between separate molecules, influencing thephysical properties of the substance.– These are the forces that hold liquids and solids together,and influence their melting and boiling points. They areweaker forces, because they result from smaller charges, orpartial charges, interacting over much larger distances.E 1 Q1 Q24πε 0dCoulomb' s Law11 Intermolecular forces include dispersion forces,dipole-dipole forces, and hydrogen bonds; iondipole forces operate between ions and molecules.12
Chapter 10 Liquids and SolidsLondon Dispersion ForcesLondon Dispersion Forces All atoms and molecules experience Londondispersion forces, which are attractive forces arisingfrom fluctuations in the electron distribution within(Fritz W. London, 1930)atoms or molecules. At any one instant, the random motion of electronswithin an atom or molecule may cause the electronsto be clustered more at one end of the particle,giving that end a very small partial negative charge,and creating a temporary instantaneous dipole: This instantaneous dipole can create induceddipoles in its neighbors by attracting or repelling itselectrons: Dispersion forces exist between all molecules, butthey are the only forces that exist between nonpolarmolecules.13London Dispersion ForcesLondon Dispersion Forces Polar molecules and ions can also induce dipoles innonpolar molecules:– This effect partially accounts for the solubility ofmolecular oxygen (nonpolar) in water and theability of blood (which contains Fe cations) tobind oxygen. London forces are generally small, with energies inthe range of 1-10 kJ/mol (most covalent bonds arewell over 100 kJ/mol) The exact magnitude of London forces in amolecules depends on the polarizability of themolecule, the ease with which a molecule’s electroncloud can be distorted by a nearby electric field.15London Dispersion ForcesNoble GasesMP ( C) BP ( C)He ——-268.8Ne -248.5Ar -189.6-245.9Kr -157.4Xe -111.5Rn -71.0-151.7-106.6-61.7F2Cl2Br2I2-185.8HalogensMP ( C) BP ( C)-219.7-188.2-101.0-34.6-7.358.8114.6184.414– Polarizability increases with the size of the atom or themolar mass of the molecule, leading to larger Londonforces and higher boiling points.– Molecules with the same molecular weight that are more“spread out” have more surface area, and therefore moreLondon forces between them.– Within a family of similar compounds (such as thehydrocarbons), London forces (and therefore boilingpoint) increase with increasing molar mass.16London Dispersion ForcesHydrocarbonsCompound Formula BP ( OctaneC8H18174.1DecaneC10H22343EicosaneC20H42 All of these molecules are isomers of the formulaC5H12, but the different arrangements of C atomsleads to a different overall shape and surface area:1718
Chapter 10 Liquids and SolidsDipole-Dipole ForcesDipole-Dipole Forces Dipole-Dipole forces are the attractions between theopposite partial charges in the permanent dipoles ofpolar molecules. The partial charges in one moleculewith a permanent dipole are attracted to the oppositepartial charges in another polar molecule: In general, for molecules of the same molecularweight, a polar molecule (dipole-dipole London)will have a higher boiling point than a nonpolarmolecule (London only):-OHHCC CHHacetoneHH Dipole-dipole forces exist between all polar molecules(in addition to London forces).2019Dipole-Dipole ForcesHydrogen Bonding Dipole-dipole forces are usually weak, 3-4 kJ/mol,and are significant only when molecules are in closecontact. The more polar the molecule, the stronger thedipole-dipole forces and the higher the boiling point. Hydrogen bonding is an especially strong versionof the dipole-dipoles force that occurs in moleculeswhich have H—N, H—O, or H—F bonds:H F HH O H OHHRRXHXHydrogen bondsX N, O, or FHHXRR HH21Hydrogen BondingH NFRNH22Hydrogen Bonding The electronegativity difference between O, N, andF vs. H is so large that these bonds are especiallypolar, and the attractions between the oppositepartial charges are especially strong. H-bonds can have energies up to 40 kJ/mol. Any molecule that contains an O—H bond, such asethanol, CH3CH2OH, is capable of forminghydrogen bonds:HHHCCHHHOHEthyl Alcohol46.07 g/molmp -117 Cbp 78.5 Cdensity 0.789 g/mol (20 C)intoxicant23HCHHOCHHDimethyl Ether46.07 g/molmp -139 Cbp -25 Cdensity 0.00195 g/mol (20 C)refrigerant24
Chapter 10 Liquids and SolidsHydrogen Bonding and Boiling PointHydrogen Bonding and Water Hydrogen bonding causes water to boil at a muchhigher temperature than would be “expected” forsuch a small molecule: Hydrogen bonding also causes solid water to adopt amore open crystalline structure, which is less densethan the liquid structure (hence, ice floats on water).25Hydrogen Bonds and the DNA Double Helix26Ion-Dipole Forces Deoxyribonucleic acid (DNA), the molecule whichencodes genetic information in living cells, consists ofa strand of sugar molecules (deoxyribose) connectedby phosphate groups; each sugar has one of four bases(A, T, G, C) attached to it. Hydrogen bonds betweenthe bases in the separate strands of DNA cause themto cling together in the famous double helix structure: Ion-Dipole forces are the result of electricalinteractions between an ion and the partial chargeson a polar molecule. These forces are responsible for the ability of polarsolvents like water to dissolve ionic compounds.sphere of hydration2827Summary: Intermolecular ForcesStrengthIntermolecularForcesFormed by theattraction between Intermolecular Forces and SolubilityExamplesIon-dipolean ion and a polarmoleculeNa and H2OHydrogen bondmolecules which haveH on N, O, or F atomsH2O and H2O; H2Oand CH3CH2OHDipole - Dipoletwo polar moleculesCH3Br and ICl;CH3Br and H2Oion and a nonpolarIon - Induced dipole anmoleculeDipole - InduceddipoleFe2 and O2 Polarity also determines whether one liquid mixeswith another liquid. The general solubility rule isthat “like dissolves like”:– Ethanol and water mix because they are bothpolar. (They are miscible with each other —soluble in all proportions.)– Oil and gasoline mix with each other becausethey are both nonpolar.– Oil and water don’t mix with each other.a polar molecule and a HCl and Cl2nonpolar moleculeLondon (dispersion) two nonpolarforcesmoleculesCH4 and CH4; F2and F2; CH4 and F22930
Chapter 10 Liquids and SolidsIntermolecular Forces and SolubilityCombinations of Intermolecular Forces When larger molecules dissolve in liquid solvents,more than one intermolecular force may beinvolved. As polar molecules become larger, ingeneral, they become less soluble in water:hydrophobic (“waterfearing”) portion31Examples: Intermolecular Forceshydrophilic (“waterloving”) portion32Examples: Intermolecular Forces1. Identify all of the kinds of intermolecular forces inthe following substances.a. CH42. What is the strongest kind of intermolecular force inthe following substances.a. CH3CH3b. CH3Clb. CH3NH2c. CH2Cl2c. Krd. CHCl3d. CH2Oe. CCl4e. CO2f.f.HClH2O2g. CH3OHg. HF33Examples: Intermolecular Forces34Examples: Intermolecular Forces3. Consider the kinds of intermolecular forces presentbetween the following substances.a. CsCl in CH3Br4. Consider the kinds of intermolecular forces presentin the following compounds, and rank the substancesin likely order of increasing boiling point.H2S (34 amu)b. CH3OH in H2OC2H6 (30 amu, C—C bond length 154 pm)c. CH3CH2CH3 in CCl4CH3OH (32 amu)d. O2 and Fe2 Ar (40 amu, radius 71 pm)e. CH3Br in H2Of.HOCH2CH2OH in H2O3536
Chapter 10 Liquids and SolidsExamples: Intermolecular ForcesIntermolecular Forces in Everyday Life5. Predict which of the following pairs of liquids aremiscible with each other.a. HOCH2CH2OH in H2O Intermolecular forces such are also responsible forthe ability of geckos to climb walls and Post-It notesto stick to surfaces:b. C6H6 (benzene) inpentane (CH3CH2CH2CH2CH3)c. octanol (CH3CH2CH2CH2CH2CH2CH2CH2OH)in octane (CH3CH2CH2CH2CH2CH2CH2CH3)3738Intermolecular Forces in Liquids and Solids Liquids and solids exist because of the relativelystrong intermolecular forces that exist between somecompounds. Intermolecular forces play a large role indetermining the physical properties of liquids.– The intermolecular forces between identicalmolecules of a substance are cohesive forces thathold the molecules of a substance together in theliquid (or solid) phase.– The intermolecular forces between differentmolecules are adhesive forces. Solids have relatively stronger intermolecular forcesthan liquids do.Liquids3940Surface TensionSurface Tension Surface Tension — molecules at the surface of aliquid feel a stronger net attraction from themolecules below than do the ones in the interior ofthe liquid. This causes the surface to act like a skincovering the liquid, and tends to shape the liquid tohave the smallest possible surface area (a sphere).Tea in space41Water Strider(ISS, April 7, 2003 )42
Chapter 10 Liquids and SolidsSurface TensionViscosity Surfactants (soaps, detergents, etc.) disrupt thehydrogen bonding at the surface of water, increasingthe ability of the water to “wet” other substances. Surface tension decreases as the intermolecularforces weaken. Viscosity is the measure of a liquid’s resistance toflowing. Viscosity is related to the ease with whichindividual molecules move around in the liquid andthus to the intermolecular forces present.H2OHgglycerol– Viscosity is measured in units of poise, P, defined as1 g cm-1 s-1 (water has a viscosity of 1 cP).– Substances composed of small, nonpolar molecules(such as gasoline and benzene) have low viscosities.– Polar molecules (such as glycerol), and moleculescomposed of long chains of atoms (such as oil andgrease) have higher viscosities.– Extremely concentrated solutions can have a highviscosity (e.g., syrup).– The viscosity of a liquid decreases at highertemperatures.4344Capillary ActionCapillary Action Capillarity (capillary action) — the rise of a liquidinside a thin glass tube, which results from thecompetition between the attractive forces betweenthe liquid molecules (cohesive forces) and the forcesbetween the liquid molecules and the walls of theglass (adhesive forces). For water, the adhesive forces are greater than thecohesive forces, and water rises in the tube, and israised slightly around the edges, producing anconcave meniscus. For mercury, the cohesive forces between Hg atomsare greater than the adhesive forces between the Hgatoms and the Si—O bonds in the glass, causingmercury to have a convex meniscus.45The Uniqueness of Water46The Uniqueness of Water Water has a low molecular mass (18.02 g/mol), butis a liquid at room temperature. The polarity and hydrogen bonding ability of watermakes it a great solvent for many substances.– The highly polar nature of the O—H bond, combinedwith water’s bent shape, makes water have a significantdipole moment.– One water molecule can hydrogen bond with up to fourothers, resulting in an unusually high boiling point(100 C) for such a small molecule.– Water dissolves many organic substances to some extent(except hydrocarbons).– Water dissolves many ionic compounds. Water has a high heat capacity, and can absorb a lotof heat without much of a temperature change.– Water can therefore be used to regulate temperatures (e.g.,in radiators).– Water regulates much of the temperature of the Earth. Water has a high surface tension, and highcapillarity– Plants draw water from soil by capillary action.4748
Chapter 10 Liquids and SolidsThe Uniqueness of WaterWater and Aquatic Life Water’s hydrogen bonds fix solid water into anopen, hexagonal structure, which is less dense thanliquid water — hence, ice floats on water. When surface water cools in the fall, its densityincreases to the maximum density of 4ºC, causing itto sink, which brings the lower-density, warmerwater from the bottom in a continuous cycle. Thisbrings dissolved nutrients and minerals to thesurface, where surface-dwelling organisms can usethem.– When a lake freezes, the layer of ice that forms at the topof the lake insulates the water below it, often preventing itfrom freezing solid.– Cells are damaged by ice crystals when they are frozen,and often do not survive when they are warmed up again.– Flash-freezing can be used to get around this problem, byfreezing the water so quickly that ice crystals don’t have achance to organize into their preferred crystal structure.5049Vaporization Vaporization — in a container of water, thermalenergy keeps the water molecules constantly movingaround. Some molecules have more energy thanothers, and are able to break free at the surface, andgo into the vapor phase. The higher the temperature,the greater the average energy of the molecules. Condensation — gas molecules that slow down canbe captured by the liquid.Phase Changes51Vapor Pressure and Dynamic Equilibrium52Vaporization When a liquid evaporates in a closed vessel, someliquid molecules acquire enough energy duringcollisions to evaporate; some of the gas moleculeseventually lose energy and return to the liquid. When the rate of evaporation equals the rate ofcondensation, there is a dynamic equilibriumbetween the two phases:Liquid h Gas The rate of vaporization increases with increasingtemperature. The rate of vaporization also increases if the surfacearea increases. Molecules with stronger intermolecular forcesevaporate with greater difficulty, and are said to benonvolatile. Molecules with weaker intermolecular forcesevaporate easily, and are said to be volatile.– Acetone (nail polish remover) and gasoline aremore volatile than water. Water is more volatilethan motor oil. Motor oil is virtually nonvolatileat room temperature.5354
Chapter 10 Liquids and SolidsThe Energetics of VaporizationVapor Pressure and Dynamic Equilibrium Vaporization is an endothermic process, whilecondensation is an exothermic process. The vapor pressure is the pressure exerted by thevapor at equilibrium with its liquid at thattemperature.– As the temperature of a liquid increases, the vaporpressure increases.– Molecules with weak intermolecular forces havehigh vapor pressures (i.e., they evaporate easily),and molecules with strong intermolecular forceshave low vapor pressures.– Sweating causes the body to feel cooler, because as waterevaporates from the skin, it absorbs energy from the skin.– Steam burns are caused when steam condenses to liquidwater on the skin, releasing heat. The amount of heat required to vaporize one mole ofa liquid to the gas phase is called the heat ofvaporization, Hºvap.Heats of Vaporization of Several Liquids at their Boiling Points and at 25ºCLiquidFormulaBoilingPoint (ºC) Hvap (kJ/mol)at BP Hvap (kJ/mol)at 25ºCWaterH2O10040.744.0Isopropyl ethyl etherC4H10O34.626.527.155Vapor Pressure and Dynamic Equilibrium56Boiling Points If a system in dynamic equilibrium is disturbed, thesystem responds so as to minimize the disturbanceand return to a state of equilibrium (Le Châtelier’sPrinciple). The boiling point of a substance is the temperatureat which the vapor pressure equals the external(atmospheric) pressure. (The normal boiling pointis the boiling point at 1 atm of pressure.)– At the boiling point, molecules in the interior of the liquidalso have enough energy to escape the liquid phase, notjust those at the surface.– The boiling point changes ifthe applied pressure ischanged: water boils at100 C at sea level, but at94 C in Denver (elevation5,280 ft) and 78 C at the topof Mt. Everest (29,035 ft).– Pressure cookers use pressureto make water to boil at ahigher temperature, allowingfood to be cooked faster.57The Clausius-Clapeyron equationExamples: Intermolecular Forces The relationship between vapor pressure andtemperature is given by the Clausius-Clapeyronequation: H vap 1 ln Pvap - C R T P H vap 11 ln 2 - T - T PR 21 1 linear formtwo-point form581. Calculate the mass of water (in g) that can bevaporized at its boiling point with 155 kJ of heat.( Hvap of H2O at 100ºC is 40.7 kJ/mol)where P is the vapor pressure, R is the gas constantin thermodynamic units (8.31 J K-1 mol-1), T is theKelvin temperature, and C is a constant.slope - Hvap/R59Answer: 68.6 g H2O60
Chapter 10 Liquids and SolidsExamples: Vapor Pressure and Boiling Point2. Which member in each pair of liquids has the highervapor pressure at a given temperature?Examples: Vapor Pressure and Boiling Point3. Which
Chapter 10 Liquids and Solids 2 Gases vs. Liquids and Solids In gases, the particles in the sample are widely separated, because the attractive forces between the particles are very weak. In liquids, there are strong intermolecular forces between the particles, which hold them in close contact, while still letting them slip and slide over
Solids, Liquids, and Gases 10 Visual Learning Company1-800-453-8481 www.visuallearningco.com 11 www.visuallearningco.com1-800-453-8481Visual Learning Company Solids, Liquids, and Gases Video Script: Solids, Liquids, and Gases 1. Think about all the things you ate or drank today.
a. liquids and solids - rigid shape b. gases - easily compressed c. gases and liquids - flow d. solids - higher density than gases e. liquids - incompressible _ 3. An open-tube manometer is used to measure the pressure in flask. The atmospheric pressure is 756 torr and the Hg column is 10.5 cm higher on the open end.
SOLIDS, LIQUIDS AND GASES HAVE DIFFERENT PROPERTIES Properties Solids Liquids Gases VOLUME SHAPE DENSITY COMPRESSIBILITY EASE OF FLOW Activity 2: Classifying solids, liquids and gases Aim: to show students that sometimes it is not easy to classify materials and that there are common misconceptions. to teach student how to discuss.
13.2 The Nature of Liquids I. A Model for Liquids A. Liquids are Fluids 1. Substances that can flow and therefore take the shape of their container B. Liquids have Relatively High Density 1. 10% less dense than solids (average) a. Water is an exception 2. 1000x more dense than gases C. Liquids are Relatively Incompressible 1.
Real Gases: Deviations from Ideal Behavior 184 11 LIquIDs AnD InTerMoLeCuLAr ForCes 193 A Molecular Comparison of Gases, Liquids, and Solids 193 Intermolecular Forces 196 Select Properties of Liquids 200 Phase Changes 201 Vapor Pressure 202 12 soLIDs AnD MoDern MATerIALs 211 Classification of Solids 211 Metallic Bonding 213 Ionic Solids 215
Chapter 10. Gases 10.1 Characteristics of Gases All substances have three phases: solid, liquid and gas. Substances that are liquids or solids under ordinary conditions may also exist as gases. These are often referred to as vapors. Many of the properties of gases differ from those of solids and liquids:
Chapter Ten- Gases Lecture Notes 10.1 Characteristics of Gases All substances have three phases: solid, liquid and gas. Substances that are liquids or solids under ordinary conditions may also exist as gases. These are often referred to as vapors. Many of the properties of gases differ from those of solids and liquids:
REVISION: ANIMAL NUTRITION & DIGESTION 19 JUNE 2013 Lesson Description In this lesson, we revise: nutrition in various animals o Herbivores, Carnivores and Omnivores the two different types of human digestion o Mechanical o Chemical Key Concepts Nutrition in Animals Nutrition is defined as the sum of the following processes – ingestion, digestion, absorption, assimilation and egestion. Some .
