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Chapter 16 Lecture

Chapter 16 Lecture. Chapter 16 A Macroscopic Description of Matter. Chapter Goal: To learn the characteristics of macroscopic systems. Slide 16-2. Chapter 16 Preview. Slide 16-3. Chapter 16 Preview. Slide 16-4. Chapter 16 Preview. Slide 16-5. Chapter 16 Preview. Slide 16-6.

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Chapter 16 Lecture

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  1. Chapter 16 Lecture

  2. Chapter 16 A Macroscopic Description of Matter Chapter Goal: To learn the characteristics of macroscopic systems. Slide 16-2

  3. Chapter 16 Preview Slide 16-3

  4. Chapter 16 Preview Slide 16-4

  5. Chapter 16 Preview Slide 16-5

  6. Chapter 16 Preview Slide 16-6

  7. Chapter 16 Preview Slide 16-7

  8. Chapter 16 Reading Quiz Slide 16-8

  9. Reading Question 16.1 What is the SI unit of pressure? • The Nm2 (Newton-meter-squared). • The atmosphere. • The p.s.i. • The Pascal. • The Archimedes. Slide 16-9

  10. Reading Question 16.1 What is the SI unit of pressure? • The Nm2 (Newton-meter-squared). • The atmosphere. • The p.s.i. • The Pascal. • The Archimedes. Slide 16-10

  11. Reading Question 16.2 One “mole” of monatomic helium means • 0.012 kg of helium. • One helium atom. • One kg of helium. • 4 helium atoms. • 6.02  1023 helium atoms. Slide 16-11

  12. Reading Question 16.2 One “mole” of monatomic helium means • 0.012 kg of helium. • One helium atom. • One kg of helium. • 4 helium atoms. • 6.02  1023 helium atoms. Slide 16-12

  13. Reading Question 16.3 The SI unit for absolute temperature is • Celsius. • Fahrenheit. • Kelvin. • Newton. • Rankine. Slide 16-13

  14. Reading Question 16.3 The SI unit for absolute temperature is • Celsius. • Fahrenheit. • Kelvin. • Newton. • Rankine. Slide 16-14

  15. Reading Question 16.4 The ideal-gas model is valid if • The gas density and temperature are both low. • The gas density and temperature are both high. • The gas density is low and the temperature is high. • The gas density is high and the temperature is low. Slide 16-15

  16. Reading Question 16.4 The ideal-gas model is valid if • The gas density and temperature are both low. • The gas density and temperature are both high. • The gas density is low and the temperature is high. • The gas density is high and the temperature is low. Slide 16-16

  17. Reading Question 16.5 An ideal-gas process in which the volume doesn’t change is called • Isobaric. • Isothermal. • Isochoric. • Isentropic. Slide 16-17

  18. Reading Question 16.5 An ideal-gas process in which the volume doesn’t change is called • Isobaric. • Isothermal. • Isochoric. • Isentropic. Slide 16-18

  19. Chapter 16 Content, Examples, and QuickCheck Questions Slide 16-19

  20. Solids, Liquids, and Gases • A solid is a rigid macroscopic system consisting of particle-like atoms connected by spring-like molecular bonds. • Each atom vibrates around an equilibrium position but otherwise has a fixed position. Slide 16-20

  21. Solids, Liquids, and Gases • A liquid is nearly incompressible, meaning the molecules are about as close together as they can get. • A liquid flows and deforms to fit the shape of its container, which tells us that the molecules are free to move around. Slide 16-21

  22. Solids, Liquids, and Gases • A gas is a system in which each molecule moves through space as a free, noninteracting particle until, on occasion, it collides with another molecule or with the wall of the container. • A gas is a fluid, and it is highly compressible. Slide 16-22

  23. Density The ratio of an object’s or material’s mass to its volume is called the mass density, or sometimes simply “the density.” The SI units of mass density are kg/m3. In this chapter we’ll use an uppercase M for the system mass and lowercase m for the mass of an atom. Slide 16-23

  24. Densities of Various Materials Slide 16-24

  25. Example 16.1 The Mass of a Lead Pipe Slide 16-25

  26. Number Density • It is often useful to know the number of atoms or molecules per cubic meter in a system. • We call this quantity the number density. • In an N-atom system that fills volume V, the number density is: The SI units of number density are m3. Slide 16-26

  27. QuickCheck 16.1 The volume of this cube is 8  102 m3. 8 m3. 8  10–2 m3. 8  10–4 m3. 8  10–6 m3. Slide 16-27

  28. QuickCheck 16.1 The volume of this cube is 8  102 m3. 8 m3. 8  10–2 m3. 8  10–4 m3. 8  10–6 m3. Slide 16-28

  29. Atomic Mass and Atomic Mass Number • The mass of an atom is determined primarily by its most massive constituents: protons and neutrons in its nucleus. • The sum of the number of protons and neutrons is called the atomic mass number:   number of protons  number of neutrons • The atomic mass, in u, is close, but not exactly, equal to the atomic mass number. • u is the atomic mass unit: 1 u  1.66  1027 kg Slide 16-29

  30. Moles and Molar Mass • By definition, one mole of matter, be it solid, liquid, or gas, is the amount of substance containing Avogadro’s number NA of particles • NA6.02  1023 mol1. • The number of moles in a substance containing N basic particles is One mole of helium, sulfur, copper, and mercury. Slide 16-30

  31. Moles and Molar Mass • If the atomic mass m is specified in kilograms, the number of atoms in a system of mass M can be found from: • The molar mass of a substance is the mass of 1 mol of substance. • The molar mass, which we’ll designate Mmol, has units kg/mol. • The number of moles in a system of mass Mconsisting of atoms or molecules with molar mass Mmol is: Slide 16-31

  32. QuickCheck 16.2 Which contains more molecules, a mole of hydrogen gas (H2) or a mole of oxygen gas (O2)? The hydrogen. The oxygen. They each contain the same number of molecules. Can’t tell without knowing their temperatures. Slide 16-32

  33. QuickCheck 16.2 Which contains more molecules, a mole of hydrogen gas (H2) or a mole of oxygen gas (O2)? The hydrogen. The oxygen. They each contain the same number of molecules. Can’t tell without knowing their temperatures. Slide 16-33

  34. Example 16.2 Moles of Oxygen Slide 16-34

  35. Temperature • What is temperature? • Temperature is related to how much thermal energy is in a system (more on this in Chapter 18). • For now, in a very practical sense, temperature is what we measure with a thermometer! • In a glass-tube thermometer, such as the ones shown, a small volume of liquid expands or contracts when placed in contact with a “hot” or “cold” object. • The object’s temperature is determined by the length of the column of liquid. Slide 16-35

  36. Temperature • The Celsius temperature scale is defined by setting TC  0 for the freezing point of pure water, and TC  100for the boiling point. • The Kelvin temperature scale has the same unit size as Celsius, with the zero point at absolute zero. The conversion from the Celsius scale to the Kelvin scale is: • The Fahrenheit scale, still widely used in the United States, is defined by its relation to the Celsius scale, as follows: Slide 16-36

  37. Temperature Slide 16-37

  38. QuickCheck 16.3 Which is the largest increase of temperature? An increase of 1F. An increase of 1C. An increase of 1 K. Both B and C, which are the same and larger than A. A, B, and C are all the same increase. Slide 16-38

  39. QuickCheck 16.3 Which is the largest increase of temperature? An increase of 1F. An increase of 1C. An increase of 1 K. Both B and C, which are the same and larger than A. A, B, and C are all the same increase. Slide 16-39

  40. Absolute Zero and Absolute Temperature • Figure (a) shows a constant- volume gas thermometer. • Figure (b) shows the pressure-temperature relationship for three different gases. • There is a linear relationship between temperature and pressure. • All gases extrapolate to zero pressure at the same temperature: T0273C. • This is called absolute zero, and forms the basis for the absolute temperature scale (Kelvin). Slide 16-40

  41. Phase Changes • Suppose you were to remove an ice cube from the freezer, initially at 20C, and then warm it by transferring heat at a constant rate. • Figure (b) shows the temperature as a function of time. • During the phase changes of melting then boiling, energy is being added to break molecular bonds, but the temperature remains constant. Slide 16-41

  42. Phase Changes • A phase diagram is used to show how the phases and phase changes of a substance vary with both temperature and pressure. • At the normal 1 atm of pressure, water crosses the solid-liquid boundary at 0C and the liquid-gas boundary at 100C. • At high altitudes, where p 1 atm, water freezes at slightly above 0C and boils at a temperature below 100C. • In a pressure cooker, p 1atm and the temperature of boiling water is higher, allowing the food to cook faster. Slide 16-42

  43. Phase Changes Food takes longer to cook at high altitudes because the boiling point of water is less than 100 C. Slide 16-43

  44. QuickCheck 16.4 If the pressure of liquid water is suddenly decreased, it is possible that the water will Freeze. Condense. Boil. Either A or B. Either A or C. Slide 16-44

  45. QuickCheck 16.4 If the pressure of liquid water is suddenly decreased, it is possible that the water will Freeze. Condense. Boil. Either A or B. Either A or C. Slide 16-45

  46. Ideal Gases • The ideal-gas model is one in which we model atoms in a gas as being hard spheres. • Such hard spheres fly through space and occasionally interact by bouncing off each other in perfectly elastic collisions. • Experiments show that the ideal-gas model is quite good for gases if two conditions are met: • The density is low (i.e., the atoms occupy a volume much smaller than that of the container), and • The temperature is well above the condensation point. Slide 16-46

  47. The Ideal-Gas Law The pressure p, the volume V, the number of moles n and the temperature T of an ideal gas are related by the ideal-gas law as follows: where R is the universal gas constant, R 8.31 J/mol K. Or: where N is the number of molecules and kB is Boltzman’s constant, kB 1.38  1023 J/K. Slide 16-47

  48. QuickCheck 16.5 If the volume of a sealed container of gas is decreased, the gas temperature Increases. Stays the same. Decreases. Not enough information to tell. Slide 16-48

  49. QuickCheck 16.5 If the volume of a sealed container of gas is decreased, the gas temperature Increases. Stays the same. Decreases. Not enough information to tell. Slide 16-49

  50. QuickCheck 16.6 Two identical cylinders, A and B, contain the same type of gas at the same pressure. Cylinder A has twice as much gas as cylinder B. Which is true? TATB TATB TATB Not enough information to make a comparison. Slide 16-50

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