Chapter 11 SOLIDS, LIQUIDS AND GASES Pearson Education, Inc.

Transcription

1 Chapter 11 SOLIDS, LIQUIDS AND GASES

2 States of Matter Because in the solid and liquid states particles are closer together, we refer to them as.

3 The States of Matter The state of matter a substance is (or are) depends on three things.

4 Bonding in Solids Which of the two substance is an amorphous solid, pyrite or obsidian?

5 Bonding in Solids There are four general types of solids. solids share a network of highly delocalized electrons. solids are sets of cations and anions mutually attracted to one another.

6 Bonding in Solids solids are joined by an extensive network of covalent bonds. solids are discrete molecules that are linked to one another only by van der Waals forces.

7 Metallic Bonding Why can metals be hit with a hammer and not break? Why are metals good conductors of heat and electricity?

8 Metallic Structure Why do some metals when hit with a hammer enough times start to tear?

9 Alloys Which of the above alloys is a substitutional alloy and which is an interstitial alloy? Which is more malleable?

10 Ionic Solids The different-sized ions in an ionic compound the distance between oppositely charged ions while keeping - charged ions away from each other.

11 What determines the crystal structure in an ionic solid? A. The size (radius) of the cation and the anion B. Minimize repulsion between the cations (and also the anions) C. Maximize attraction between the cations and anions D. All of the above Do the anions touch each other in any of these three structures? If not, which ions do touch each other? A. Yes, if the anions are sufficiently large. B. Yes, if the anions are sufficiently small. C. No, because anions repel one another. D. No, because each anion adopts different lattice points in the unit cell.

12 Covalent-Network and Molecular Solids are an example of a covalent-network solid, in which atoms are covalently bonded to each other. They tend to be hard and have high melting points.

13 Covalent-Network and Molecular Solids is an example of a molecular solid, in which atoms are held together with van der Waals forces. They tend to be softer and have lower melting points.

14 How many bonds does each carbon atom in C 60 make? Based on this observation would you expect the bonding in C 60 to be more like that in diamond or that in graphite? A. Four bonds and bonding is like that in diamond. B. Four bonds and bonding is like that in graphite. C. Three bonds and bonding is like that in diamond. D. Three bonds and bonding is like that in graphite.

15 Summarizing Intermolecular Forces

16 In which substance, benzene or toluene, are the intermolecular forces stronger? In which substance do the molecules pack more efficiently? A. Benzene possesses stronger intermolecular forces and has molecules packed more efficiently. B. Benzene possesses stronger intermolecular forces and toluene has molecules packed more efficiently. C. Toluene possesses stronger intermolecular forces and has molecules packed more efficiently. D. Toluene possesses stronger intermolecular forces and benzene has molecules packed more efficiently.

17 Intermolecular Forces The attractions between molecules nearly as strong as the intramolecular attractions that hold compounds together.

18 Intermolecular Forces vs Intramolecular Forces 427 KJ/mol 15.2 KJ/mol

19 Intermolecular Forces These intermolecular attractions are, however, strong enough to control properties, such as boiling and melting points, vapor pressures, and viscosities.

20 London Dispersion Forces Another helium atom nearby, then, would have a dipole induced in it, as the electrons on the left side of helium atom 2 repel the electrons in the cloud on helium atom 1.

21 Factors Affecting London Forces The shape of the molecule affects the strength of dispersion forces: long, skinny molecules (like n-pentane) tend to have stronger dispersion forces than short, fat ones (like neopentane). This is due to the increased in n- pentane.

22 Factors Affecting London Forces The strength of dispersion forces tends to increase with increased molecular weight. Larger atoms have larger electron clouds that are easier to.

23 How do the halogens indicate ldf strength?

24 Dipole Dipole Interactions The more the molecule, the higher its boiling point.

25 Which Have a Greater Effect? Dipole Dipole Interactions or Dispersion Forces If two molecules are of comparable size and shape, dipole dipole interactions will likely be the force. If one molecule is much larger than another, forces will likely determine its physical properties.

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27 Using the terms H-bonding, dipole-dipole interaction and electronegativity explain the following trends in boiling point.

28 Which compound below is not capable of forming hydrogen bonds? a. CH 4 b. NH 3 c. H 2 O d. HF

29 To form a hydrogen bond what must the nonhydrogen atom (N, O, or F) involved in the bond possess? A. The non-hydrogen atom must have a nonbonding electron pair. B. The non-hydrogen atom must have low electronegativity. C. The non-hydrogen atom must have a large atomic size. D. The non-hydrogen atom must have a small electron affinity.

30 Which force below is the strongest intermolecular attractive force? a. Hydrogen bonding b. Ion-dipole forces c. Dipole-dipole forces d. London dispersion forces

31 A. CH 3 OH in water, because CH 3 OH is a strong electrolyte and forms ions. B. Ca(NO 3 ) 2 in water, because Ca(NO 3 ) 2 is a strong electrolyte and forms ions. C. CH 3 OH in water, because CH 3 OH is a weak electrolyte and forms ions. D. Ca(NO 3 ) 2 in water, because Ca(NO 3 ) 2 is a weak electrolyte and forms ions.

32 Intermolecular Forces Affect Many Physical Properties The strength of the attractions between particles can greatly affect the properties of a substance or.

33 Which element below has the highest boiling point? a. Kr b. F 2 c. Cl 2 d. Br 2

34 A. CH 4 < CBr 4 < CCl 4 B. CCl 4 < CH 4 < CBr 4 C. CH 4 < CCl 4 < CBr 4 D. CBr 4 < CCl 4 < CH 4

35 A. CBr 4 because dispersion forces between its molecules are greater than in CCl 4. B. CBr 4 because polar forces between its molecules are smaller than in CCl 4. C. CCl 4 because polar forces between its molecules are greater than in CBr 4. D. CCl 4 because dispersion forces between its molecules are smaller than in CBr 4.

36 Surface Tension Surface tension results from the net force experienced by the molecules on the surface of a liquid.

37 Viscosity Resistance of a liquid to flow is called. It is related to the ease with which molecules can move past each other. Viscosity with stronger intermolecular forces and decreases with higher temperature.

38 Which liquid below is the least viscous? a. water b. hydrogen peroxide c. glycerol (1,2,3-propanetriol) d. all the above have equal viscosity

39 A. Viscosity increases as intermolecular forces increase while surface tension decreases. Both viscosity and surface tension increase with increasing temperature. B. Viscosity decreases as intermolecular forces increase while surface tension increases. Both viscosity and surface tension increase with decreasing temperature C. Both viscosity and surface tension increase as intermolecular forces increase and temperature decreases. D. Both viscosity and surface tension decrease as intermolecular forces increase and temperature increases.

40 Phase Changes

41 A. Melting (or fusion) and endothermic B. Melting (or fusion) and exothermic C. Freezing and endothermic D. Freezing and exothermic

42 Energy Changes Associated with Changes of State The heat added to the system at the melting and boiling points goes into pulling the molecules farther apart from each other. The temperature of the substance does not rise during a phase change.

43 Heating Curves Draw a heating curve for benzene (bp of 80 o C and fp of 6 o C) if the heat added is equal.

44 When heat is added to ice at zero degrees Celsius, what will happen? a. The temperature will increase. b. The temperature will decrease. c. The temperature will not change. d. A supercritical fluid will form.

45 Substance X has a boiling point of 150 degrees F and a freezing point of 15 degrees F. The condensation point of X a. is 150 degrees F. b. is 15 degrees F. c. is 165 degrees F. d. is 135 degrees F.

46 As the temperature increases, does the rate of molecules escaping into the gas phase increase or decrease? A. Increases B. Decreases

47 Energy Changes Associated with Changes of State What types of IMF can explain the heat of phase change for each of the above substances?

48 Isopropyl alcohol feels cool to the touch because it has an (X) heat of (Y). a. X = exothermic, Y = vaporization b. X = endothermic, Y = vaporization c. X = exothermic, Y = fusion d. X = endothermic, Y = fusion

49 The energy required to cause a liquid to boil is called the of the liquid. a. boiling point b. freezing point c. heat of vaporization d. heat of fusion

50 Is it possible to calculate the heat of sublimation for a substance given its heats of vaporization and fusion? If so, what is the relationship? A. No, because we are not dealing with state functions. B. No, because we need heat of melting. C. Yes, ΔH sub = ΔH fus + ΔH vap D. Yes, ΔH sub = ΔH fus ΔH vap

51 How can a small molecule like water, have a higher boiling point than ether or ethanol? Use line angle formulas and the types of IMF to explain the boiling point of the three organic liquids.

52 What is the boiling point of water at the top of Mt. Everest where atmospheric pressure is 400 mmhg? A. 20 o C B. 60 o C C. 80 o C D. 100 o C What is the vapor pressure of ethylene glycol at its normal boiling point? A. 260 torr B. 460 torr C. 660 torr D. 760 torr

53 Vapor Pressure The natural log of the vapor pressure of a liquid is inversely proportional to its temperature. The slope of the line is called the equation: ln P = H vap /RT + C, where C is a constant

54 Vapor Pressure The liquid and vapor reach a state of : liquid molecules evaporate and vapor molecules condense at the same rate.

55 What does a phase diagram show about a substance?

56 Phase Diagram of Water

57 The temperature and pressure at which all three phases exist simultaneously is called the point of a substance. a. boiling b. freezing c. triple d. critical

58 If the temperature of water is increased from -20 o C to 120 o C, while the pressure is held constant, what type of phase transition will occur? A. Melting B. Vaporization C. Both of the above D. Neither of the above If the pressure exerted on a water is increased, while the temperature is held constant at 0 o C, what type of phase transition will eventually occur? A. Freezing B. Melting C. Vaporization D. Condensation

59 Which substance below has a greater density in its liquid state than in its solid state? a. Iron b. Glass c. Water d. Carbon dioxide

60 For a given substance, do you expect the density of the substance in its liquid state to be closer to the density in the gaseous state or in the solid state? A. Closer to the density of a gas B. Closer to the density of a solid C. Both are somewhat close to one another in density. D. They are significantly different in density.

61 Why is the boiling point of SnH 4 higher than that of CH 4? A. SnH 4 is more polar than CH 4. B. SnH 4 is smaller in size than CH 4. C. SnH 4 has greater internal dispersion forces than in CH 4. D. SnH 4 is ionic in structure and CH 4 is molecular.

62 Which compound below has the highest boiling point? a. H 2 O b. H 2 S c. H 2 Se d. H 2 Te

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64 If the inside surface of each tube were coated with wax, would the general shape of the water meniscus change? Would the general shape of the mercury meniscus change? Shape of Water Meniscus Shape of Hg Meniscus A. Yes, Inverted U Yes, downward U B. No change Yes, downward U C. No change No change D. Yes, Inverted U No change