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Liquids and Solids

13. Liquids and Solids. Chapter Goals. Kinetic-Molecular Description of Liquids and Solids Intermolecular Attractions and Phase Changes 分子間引力及相的改變 The Liquid State Viscosity 黏度 Surface Tension 表面張力 Capillary Action 毛細現象 Evaporation 蒸發 Vapor Pressure 蒸氣壓

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Liquids and Solids

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  1. 13 Liquids and Solids

  2. Chapter Goals • Kinetic-Molecular Description of Liquids and Solids • Intermolecular Attractions and Phase Changes分子間引力及相的改變 The Liquid State • Viscosity 黏度 • Surface Tension 表面張力 • Capillary Action 毛細現象 • Evaporation 蒸發 • Vapor Pressure 蒸氣壓 • Boiling Points and Distillation 沸點和蒸餾 • Heat Transfer Involving Liquids 液體之熱傳導

  3. Chapter Goals The Solid State • Melting Point 熔點 • Heat Transfer Involving Solids 固體之熱傳導 • Sublimation and the Vapor Pressure of Solids 昇華及固體之蒸氣壓 • Phase Diagrams (P versus T) 相圖 • Amorphous Solids and Crystalline Solids非晶固態及結晶固態 • Structures of Crystals 結晶的結構 • Bonding in Solids 固體之鍵結 • Band Theory of Metals金屬能帶理論

  4. Kinetic-Molecular Description of Liquids and Solids • Solids and liquids are condensed states壓縮狀態 • The atoms, ions, or molecules in solids and liquids are much closer to one another than in gases. • Solids and liquids are highly incompressible不能壓縮的 • Liquids and gases are fluids流動的. • They easily flow. • Theintermolecular attractions in liquids and solids are strong. 液體及固體之分子間的引力很強

  5. Kinetic-Molecular Description of Liquids and Solids • Schematic representation of the three common states of matter. • The process in which a liquid changes to a solid • Solidification • Crystallization • A more specific term • The formation of a very ordered solid material

  6. Kinetic-Molecular Description of Liquids and Solids • If we compare the strengths of interactionsamong particles and the degree of orderingof particles, we see that Gases< Liquids < Solids • Miscible可溶混的liquidsare soluble in each other. • Examples of miscible liquids: • Water dissolves in alcohol. • A drop of red ink in the water • Gasoline dissolves in motor oil. Diffusion The miscibility of two liquids refers to their ability to mix and produced a homogeneous solution均質溶液

  7. Diffusion in solids:very slowly

  8. Kinetic-Molecular Description of Liquids and Solids • Immiscible liquidsare insoluble in each other. • Two examples of immiscible liquids: • Water does not dissolve in oil. • Water does not dissolve in cyclohexane 環已烷

  9. Intermolecular Attractions and Phase Changes • Intermolecular forces 分子間作用力 • The forces between individual particles (atoms, molecules, ions) of a substance • Intramolecular forces 分子內作用力 • Covalent and ionic bonds within compounds Covalent bonds 共價鍵結 Intramolecular forces hydrogen bonding 氫鍵 Intermolecular forces

  10. 分子間吸引力是物質中個別粒子 (包括原子、分子或離子) 間的作用力，此種作用力遠小於分子內作用力，即化合物內原子間所形成的共價鍵與離子鍵結。

  11. Intermolecular Attractions and Phase Changes • There are four important intermolecular attractions. • This list is from strongest attraction to the weakest attraction. • Ion-ion interactions離子- 離子作用力 • The force of attraction between two oppositely charged ions is governed by Coulomb’s law庫侖定律. Energy has the units of forces x distance, Fxd The energy of attraction, E F  q+ and q- are the ion charges. d is the distance between the e ions F is the force of attraction (q+)(q-) (q+)(q-) E  d2 d ※ 庫侖定律：在真空中，兩個靜止點電荷之間的相互作用力的大小與兩點電荷電量大小乘積成正比，與距離平方成反比。

  12. Intermolecular Attractions and Phase Changes • Most ionic bonding is strong have relatively high melting points • Ionic substances containing multiply charged ions, such as Al3+, Mg2+, O2-, and S2-, usually have higher melting and boiling points than ionic compounds containing only singly charged ions, such as Na+, K+, F-, Cl-. • For a series of ions of similar charges, the closer approached ions of smaller ions result in stronger interionic attractive forces and higher melting points (NaF, NaCl, NaBr)

  13. Intermolecular Attractions and Phase Changes • Coulomb’s law determines: • The melting and boiling points of ionic compounds. • The solubility of ionic compounds. Example 13-1: Arrange the following ionic compounds in the expected order of increasing melting and boiling points. NaF, CaO,CaF2 Na+F- < Ca2+F2-<Ca2+O2-

  14. Intermolecular Attractions and Phase Changes • Dipole-dipole interactions 偶極- 偶極作用 • 在極性分子中,有正及負兩極,分子帶正電之一端吸引另一分子帶負電的一端,即稱之 • 使得極性分子間的引力大於非極性分子 • 偶極─偶極吸引力一般僅是共價鍵及離子鍵強度的百分之一，它們的強度會隨偶極之間距離的增加而變小 • BrF

  15. Intermolecular Attractions and Phase Changes • Hydrogen bonding氫鍵 • Very strong dipole-dipole interaction • Strong hydrogen bonding occurs among polar covalent molecules containing H(hydrogen bond donor) and one of the three small, highly electronegative elements — F, O or N (hydrogen bond acceptor) • Consider H2O a very polar molecule.

  16. Intermolecular Attractions and Phase Changes Hydrogen bond

  17. Intermolecular Attractions and Phase Changes • London Forces (Dispersion forces; 分散力) • They are the weakest of the intermolecular forces. • This is the only attractive force in nonpolar molecules such as O2, N2 and monatomicspecies such as the noble gases. • Without dispersion forces, such substance could not condense to form liquids or solidify to form solids

  18. Intermolecular Attractions and Phase Changes • In a group of Ar atoms the temporary dipole in one atom induces other atomic dipoles. • The positively charged nucleus • The electron clouds of an atom in nearby molecules • Dispersion forces are generally stronger for molecules that are larger • They exist in all substances

  19. 倫敦分散力 (London dispersion forces) 非極性原子或分子間的作用力稱為倫敦分散力，此種作用力是原子或分子在移動時，其電子雲會產生瞬間偶極距 (instantaneous dipole moments)，此時非極性原子或分子間藉由此種瞬間偶極相互吸引，稱之為倫敦分散力，又可稱之為瞬間偶極距-瞬間偶極距作用力。

  20. 分子間作用力的比較 • 倫敦分散力存在於所有分子中，其強度隨分子量的增加而增加，也與分子的形狀有關。除了倫敦分散力，極性分子間存在的另一種作用力稱為偶極-偶極作用力。 • 氫鍵則是鍵結在高電負度原子上之氫原子與另一高電負度原子間之作用力，是所有分子間作用力中最強的一種作用力。 • 不過上述不論那種分子間作用力，其強度皆比共價鍵或離子鍵弱很多。

  21. 恆久偶極矩 23

  22. 分子間作用力

  23. 分子間作用力的判斷

  24. Intermolecular Attractions and Phase Changes • Example 13-1: Intermolecular Forces • Identify the type of intermolecular forces that are present in a condensed phase sample of each of the following. For each, make a sketch, including a few molecules, that represents the major type of force. (a) water, H2O (b) iodine, I2 (c) nitrogen dioxide, NO2. • water, H2O • polar • H, O hydrogen bonds • The London forces • (b) iodine, I2 • Nonpolar the London forces • (c) nitrogen dioxide, NO2 • polar • Dipole-dipole interactions • The London forces 26

  25. The Liquid State Viscosity 黏度 • Viscosity is the resistanceto flow. • For example: molasses糖蜜, syrup糖漿or honey. • Oil for your car is bought based on this property. • 10W30 or 5W30 describes the viscosity of the oil at high and low temperatures. • Measure by Viscometer. • The stronger of the intermolecular forces of attraction the more viscosity • Increasing the size and surface area of molecule genernally results in increased viscosity • Temperature increase viscosity decrease Pentane C5H12戊烷 黏度是液體內部抵抗液體流動的阻力，當液體的黏度愈大，液體就愈不容易流動。液體的黏度大小與液體分子間作用大小有關，分子間作用力愈大，黏度愈大。 Dodecane C12H26十二烷

  26. The Liquid State Surface Tension表面張力 • Surface tension is a measure of the unequal attractions that occur at the surface of a liquid. • The molecules at the surface are attracted unevenly. 液體表面分子僅受到液面下方的分子吸引！此現象導致液體表面分子感受到往液內的淨吸引力。因此，液面分子隨時受到一個向下的拉力，此力即稱『表面張力』。當分子間的作用力愈強時，表面張力愈大

  27. The Liquid State Capillary Action 毛細作用 • Capillary action is the ability of a liquid to rise (or fall) in a glass tube or other container 當一根直徑細小的玻璃管或毛細管放在水中時，水會在細管中往上升，此種液態在細管中爬升的現象稱為毛細作用 • Cohesive forces內聚力are the forces that hold liquids together. 內聚力表示:液體分子間的作用力 • Adhesive forces 吸附力 are the forces between a liquid and another surface. 吸附力表示:液體分子與管壁間的附著力 • Capillary rise implies that the: • Adhesive forces > cohesive forces • Capillary fall implies that the: • Cohesive forces > adhesive forces • The smaller the bore, the higher the liquid climbs

  28. The Liquid State • Capillary action also affects the meniscus of liquids.毛細現象會影響圓筒內液體的凹凸面 concave convex Adhesive forces < cohesive forces Adhesive forces > cohesive forces 水與玻璃管的吸附力大於水分子間的內聚力，因此呈現下凹的液面 汞分子間的內聚力大於汞與玻璃管的吸附力，因此呈現上凸的液面

  29. The Liquid State Evaporation 蒸發 • Evaporation is the process in which molecules escape from the surface of a liquid and become a gas.物質從液體表面變為氣體狀態的過程

  30. The Liquid State • Evaporation is temperature dependent. • The rate of evaporation increases as temperature increases Only the higher-energy molecules can escape from the liquid phase

  31. The Liquid State • Condensation 凝結; 冷凝 • In a closed container • Dynamic equilibrium evaporation liquid vapor condensation • LeChatelier’s Principle勒沙特列原理 • If the vessel were left open to the air, the equilibrium could not be reached. • A liquid can eventually evaporated entirely 33

  32. The Liquid State Vapor Pressure 蒸氣壓 • Vapor pressure is the pressure exerted by a liquid’s vapor on its surface at equilibrium. • Vapor Pressure (torr) and boiling point for three liquids at different temperatures. 0oC20oC30oCnormal boiling point diethyl ether乙醚 185 442 647 36oC Ethanol 酒精 12 44 74 78oC water 水 5 18 32 100oC • Vapor pressures of liquids alwaysincrease as temperature increase 液體的沸點是液體的表面蒸氣壓等於外界壓力時的溫度

  33. The Liquid State Vapor Pressure 蒸氣壓 Easily vaporized liquids are called volatile liquids揮發性液體 Stronger cohesive forces tend to hold molecules in the liquid state Methanol molecules are strongly linked by hydrogen bond lower vapor pressure Dispersion forces increase with increasing molecular size larger molecules have lower vapor pressure 35

  34. The Liquid State Vapor Pressure 蒸氣壓 Vapor pressure can be measured with manometers壓力計 36

  35. The Liquid State Vapor Pressure as a function of temperature 液體的沸點是液體的表面蒸氣壓等於外界壓力時的溫度

  36. The Liquid State Boiling Points 沸點 and Distillation蒸餾 • The boiling point is the temperature at which the liquid’s vapor pressure is equal to the applied pressure (usually atmospheric大氣壓). • The normalboiling point正常沸點is the boiling point when the pressure is exactly 1 atm (760 torr). 當外界壓力等於一大氣壓時，此溫度稱為正常沸點 • If the applied pressure is lower than 1 atom water boil below 100oC. • 物質的沸點高低與分子間作用力有直接的關係。當分子間作用力愈大，沸點愈高。 • Distillation蒸餾is a method we use to separate mixtures of liquids based on their differences in boiling points.

  37. The Liquid State Distillation蒸餾 • Different liquids have different vapor pressure and boil at different temperature. • Distillation is a process in which a mixture or solution is separated into its components on the basis of the differences in boiling points of the components. • Distillation is another vapor pressure phenomenon.

  38. The Liquid State Distillation蒸餾 40

  39. The Liquid State Heat Transfer Involving Liquids • Heat must added to a liquid to raise its temperature • The amount of heat that must be added to the stated mass of liquid to raise its temperature by one degree Specific heat (J/goC) 比熱 • molar heat capacity (J/moloC)莫耳熱容量 (使1mol物質上升1oC所需的熱量 • Molar heat (enthalpy焓) of vaporization莫耳汽化熱 改變1 mol 物質由液態形成氣態所需的能量 • 水在100oC 的莫耳汽化熱為40.7 kJ/mol

  40. The Liquid State 1000J mol KJ 18g x 40.7KJ/mol= 40.7x = 2.26x103 J/g 42

  41. The Liquid State Heat Transfer Involving Liquids Condensation Heat of condensation 凝結熱 liquid + heat vapor evaporation condensation 43

  42. The Liquid State Example 13-2: How much heat is released by 2.00 x 102 g of H2O as it cools from 85.0oC to 40.0oC? The specific heat of water is 4.184 J/goC. q=mCT ?J = 2.00 x 102 g x (4.184J/goC) x( 85.0-40oC) ?J = 3.76x104 J = 37.6kJ 44

  43. 1mol 46g 113J moloC The Liquid State Example 13-3: The molar heat capacity of ethyl alcohol, C2H5OH, is 113 J/moloC. How much heat is required to raise the T of 125 g of ethyl alcohol from 20.0oC to 30.0oC? 1 mol C2H5OH = 46.0 g ?mol C2H5OH = 125g x =2.72 mol C2H5OH ?J = 2.72mol x x (30.0-20.0oC) = 3.07 KJ

  44. +2260J -2260J The Liquid State • The calculations we have done up to now tell us the energy changes as long as the substance remains in a single phase. • Next, we must address the energy associated with phase changes. • For example, solid to liquid or liquid to gas and the reverse. • Heat of Vaporization is the amount of heat required to change 1.00 g of a liquid substance to a gas at constant temperature. • Heat of vaporization has units of J/g. • Heat of Condensation is the reverse of heat of vaporization, phase change from gas to liquid. 1.0g H2O(l) at 100oC 1.0g H2O(g) at 100oC

  45. +40.7kJ -40.7kJ The Liquid State Molar heat of vaporization or DHvap • The DHvap is the amount of heat required to change 1.00 mole of a liquid to a gas at constanttemperature. DHvap has units of J/mol. Molar heat of condensation • The reverse of molar heat of vaporization is the heat of condensation. 1.0mol H2O(l) at 100oC 1.0mol H2O(g) at 100oC

  46. The Liquid State 加熱／冷卻曲線 (heating-cooling curve)

  47. 1mol 18g 36.4J 75.3J moloC moloC 40.7x103J mol The Liquid State Example 13-4: How many joules of energy must be absorbed by 5.00 x 102 g of H2O at 50.0oC to convert it to steam at 120oC? The molar heat of vaporization of water is 40.7 kJ/mol and the molar heat capacities of liquid water and steamare 75.3 J/mol oC and 36.4 J/mol oC, respectively. 50oC H2O(l) 100oC H2O(l) 100oC H2O(g) 120oC H2O(g) ?mol H2O = 500g x =27.8 mol H2O ?J = 27.8mol x x (100.0-50.0oC) = 1.05x105 J ?J = 27.8mol x = 11.31x105 J ?J = 27.8mol x X (120.0-100.0oC) = 0.20x105 J Total J = 1.05x105 + 11.31x105 + 0.2x105 = 12.56 x105 J or 1.26x103 kJ

  48. 1mol 1mol 18g 18g The Liquid State Example 13-5: If 45.0 g of steam at 140oC is slowly bubbled into 450 g of water at 50.0oC in an insulated container, can all the steam be condensed? ?mol steam = 45.0g x =2.5 mol steam ?mol H2O = 450g x =25.0 mol H2O Calculate the amount of heat required to condense the steam 2.5mol x(36.4J/moloC)x(140-100oC)+2.5 mol x (40.7kJ/mol) =105.4kJ Calculate the amount of heat available in the liquid water 25.0mol x (75.3J/moloC)x(100.0-50oC) = 94.1kJ Amount of heat to condense all of the steam is 105kJ Amount of heat that the liquid water can absorb is 94.1kJ Thus all of the steam cannot be condensed

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