1. The Nature of Gases
Chapter 10 section 1

2. Kinetic theory
kinetic energy – the energy an object has because of its motion
kinetic theory – the tiny particles in all forms of matter are in constant motion

3. Kinetic Theory of Gases
A gas consists of small particles that
move rapidly in straight lines
have essentially no attractive forces 3

4. are very far apart
have very small volumes compared to the volumes of the containers they occupy
have kinetic energies that increase with an increase in temperature

5. Properties of Gases Gases are described in terms of four properties:
pressure (P)
volume (V)
temperature (T)
amount (n) 5

7. Gas Pressure gas pressure – the force acting on a specific area
The force is the result of billions of gas particles simultaneously colliding with the object.

8. Vacuum – empty space where there are no gas particles, no collisions and therefore no force or pressure.

9. Atmospheric pressure
is the pressure exerted by a column of air from the top of the atmosphere to the surface of the Earth

10. altitude weather. Is about 1 atmosphere at sea level. Depends on
Is lower at high altitudes where the density of air is less.
Is higher on a rainy day than on a sunny day.

12. barometer - device used to measure atmospheric pressure
indicates atmospheric pressure as the height in mm of a column of mercury 12

13. Formula Pressure (P) = force area Pressure units:
pascal (Pa) – SI unit
millimeters of mercury (mmHg)
atmospheres (atm)

14. standard atmosphere (atm) – pressure required to support 760 mm of mercury in a mercury barometer at 25ºC.

15. Conversion Factors 1 atm = 760 mmHg (exact) 1 torr = 1 mmHg
1 atm = 760 torr
1 atm = lb/in.2
1 atm = kPa

16. Learning Check A. What is 475 mmHg expressed in atmospheres (atm)?
3) x 105 atm
B. The pressure in a tire is 2.00 atm. What is this pressure in mmHg?
1) mmHg
2) 1520 mmHg
3) mmHg 16

17. Solution A. What is 475 mmHg expressed in atm? 2)
475 mmHg x 1 atm = atm
760 mmHg
B. The pressure of a tire is measured as 2.00 atm. What is this pressure in mmHg?
2.00 atm x mmHg = mmHg
1 atm 17

18. temperature
temperature is a measure of the average kinetic energy of the molecules that make up a substance.
Increase in average kinetic energy causes the temperature to rise
Decrease in average kinetic energy causes temperature to drop.

19. Particles with no kinetic energy have no motion and no temperature.
Absolute zero is the temperature at which the motion of particles theoretically stops.
Absolute zero = ºK

20. Kelvin temperature scale reflects the relationship between temperature and average kinetic energy.
The Kelvin temperature of a substance is directly related to average kinetic energy of its particles.
Particles at 200 ºK have twice the kinetic energy as particles at 100 ºK.

21. Learning Check
A cylinder of oxygen gas is cooled from 300K (27 ºC) to 150 K (-123 ºC). By what factor does the average kinetic energy of the oxygen molecules in the cylinder decrease?

22. Solution
Since there is a direct relationship between Kelvin temperature and average kinetic energy the factor is
150 K = or K = 2
300 K K

23. Learning Check
Would you expect to find negative temperatures on the Kelvin temperature scale?

24. Solution
Since temperature is a measure of the average kinetic energy (motion) of particles and 0 ºK implies the absence of movement, no.

25. The Nature of Liquids
Chapter 10 section 2

26. Particles in liquids are
in motion
free to slide past one another
like gases and can flow
unlike gases in that they do have intermolecular attractive forces between them
hydrogen bonds
dipole-dipole interactions

27. Intermolecular forces cause liquids to have a definite volume rather than being able to fill their containers
increasing pressure will not effect the volume of a liquid
like solids, liquids are known as condensed states of matter.

28. vaporization – conversion of a liquid into a gas
evaporation – conversion of a liquid into a gas from the surface of a liquid that is not boiling.
condensation – conversion of a gas into a liquid

29. Heat increases the rate of evaporation.
Evaporation, however, is a cooling process.
The molecules with the highest amount of kinetic energy are the ones that evaporate.
With the loss of these molecules, the average amount of kinetic energy is reduced and temperature drops.

30. Vapor Pressure
When liquids are in a closed container, evaporation still occurs.
Condensation also occurs.
Equilibrium occurs when the number of particles evaporating equals the number of particles condensing.
Evaporation Condensation
- called - dynamic equilibrium

31. The gas particles in the closed container exert pressure on the container.
Vapor pressure – force due to the collision of the gas particles above a liquid in a closed container.

32. Vapor pressure increases with increase in temperature.
Manometer – device that measures the vapor pressure of a liquid.

33. When temp reaches a high enough level, most particles in the liquid have the kinetic energy to overcome their intermolecular forces and change into a gas.
This causes boiling.
Boiling - vaporization throughout a liquid

34. Boiling point is the temp at which the vapor pressure of the liquid is equal to the external pressure (atmospheric pressure).
Bubbles of vapor form inside the liquid and rise to the surface and escape as the liquid boils.

35. Boiling is cooling process just like evaporation.
As a result, temperature of a boiling liquid never rises above its boiling point.

36. normal boiling point – boiling point of a liquid at a pressure of 101
normal boiling point – boiling point of a liquid at a pressure of 101.3kPa or 1 atm.
increases as pressure increases.
decreases as pressure decreases.

37. In Boston which is at sea level where atmospheric pressure is 101
In Boston which is at sea level where atmospheric pressure is 101.3kPa, boiling point of water is 100 ºC.
In Denver which is 1600 m above sea level where atmospheric pressure is 85.3kPa, boiling point of water is 95 ºC.

38. Learning Check
Would it take longer to boil pasta in Boston or Denver? Why?

39. Solution
Longer in Denver because boiling water is not as hot. (95 ºC instead of 100)

40. Learning Check
Why do foods cook faster in a pressure cooker?

41. Solution
In a pressure cooker, water boils well above 100 ºC.

42. The Nature of Solids
Chapter 10 section 3

43. Particles in a solid Tend to vibrate in a fixed position
Are packed against one another in a highly organized pattern
Have a definite shape and volume

44. Changes in state melting – solid turns into a liquid
freezing – liquid changes into a solid

45. melting point – temperature at which a solid turns into a liquid
freezing point – temperature at which a liquid turns into a solid

46. For any given solid, the melting point and freezing point are the same temperature.
At this temperature, the solid and liquid substance are in equilibrium.
Solid Liquid

47. Most solids are crystals.
Crystal – solid substance in which the particles are arranged in an orderly, repeating, 3-dimensional pattern.

48. The type of bonding that exists between the atoms determines the melting points of crystals.
Ionic solids have relatively high melting points
Molecular solids (w covalent bonds) have relatively low melting points

49. Allotropes – 2 or more different molecular forms of the same element in the same physical state.
Example; carbon has 3 allotropes

50. buckminsterfullerine
1985 buckminsterfullerine (buckyballs) discovered. Molecule with 60 or more C atoms arranged into a structure like a soccer ball.

51. diamond
Buckminsterfullerene -buckyball
graphite

52. amorphous solids – non-crystalline solids whose atoms are randomly arranged.
Examples: rubber, plastic, asphalt, glass

53. Changes of State
Chapter 10 Section 4

55. Heat of Fusion
the amount of heat released when 1 gram of liquid freezes (at its freezing point)
the amount of heat needed to melt 1 gram of a solid (at its melting point) 55 55

56. for water (at 0 °C)
Heat of = J or 80 cal
Fusion g of water

58. Calculations Using Heat of Fusion
How much heat in calories is needed to melt 15.0 g of ice at 0 °C ?
STEP 1
Given: g of water(s)
Change of state: melting at 0 °C 58 58

59. STEP 2
Plan:
g of water(s) g of water(l)
STEP 3
Write conversion factors:
1 g water = cal
1 g water and cal
80 cal g water

60. Set up the problem to calculate calories:
STEP 4
Set up the problem to calculate calories:
15.0 g water x cal = cal
1 g water 60 60

61. Learning Check
How many joules are released when 25.0 g of water at 0 °C freezes?
1) 334 J
2) J
3) J 61 61

62. Solution STEP 1 Given: 25.0 g of water (l)
change of state: freezing at 0 °C
STEP 2
Plan: g water (l) g of water (s) 62 62

63. STEP 3
Write conversion factors:
1 g of water = 334 J
1 g of water and __334 J___
334 cal g of water

64. Set up the problem to calculate joules:
STEP 4
Set up the problem to calculate joules:
25.0 g water x J = J (3)
1 g water 64 64

66. Sublimation occurs when a solid changes directly to a gas
takes place in frost-free refrigerators
is used to prepare freeze-dried foods for long-term storage 66 66

67. dry ice (solid CO2) sublimes at 78 C

69. condenses when gas molecules lose energy and form a liquid
Water
evaporates when molecules on the surface gain sufficient energy to form a gas
condenses when gas molecules lose energy and form a liquid 69 69

70. Water
boils when molecules acquire the energy to change into a gas forming bubbles throughout the liquid 70 70

71. Heat of vaporization
the amount of heat absorbed to vaporize 1 g of a liquid to gas at the boiling point
the amount of heat released when 1 g of a gas condenses to liquid at the boiling point

72. Boiling Point of Water = 100 °C Heat of = 2260 J or 540 cal
Vaporization g of water
(water) 72 72

73. 73 73

74. Learning Check
How many kilocalories (kcal) are released when 50.0 g of water(g) as steam from a volcano condenses at 100 °C?
1) 27 kcal
2) 540 kcal
3) kcal 74 74

75. Solution STEP 1 Given: 50.0 g of water(g)
Change of state: condensing at 100 °C
STEP 2
Plan:
g of water(g) g of water(l) 75 75

76. Write conversion factors: 1 g of water = 540 cal
STEP 3
Write conversion factors:
1 g of water = 540 cal
1 g of water and cal
540 cal g of water
1 kcal = cal
1 kcal and cal
1000 cal kcal

77. Set up the problem to calculate kilocalories:
STEP 4
Set up the problem to calculate kilocalories:
50.0 g water x cal x 1 kcal = 27 kcal
1 g water cal 77 77

78. 78 78

79. Phase diagram
diagram that gives the conditions of temperature and pressure at which a substance exists as a solid, liquid and gas.
Lines separating regions (phases) give the conditions in which the two phases exist in equilibrium

80. For water triple point is
triple point – on a phase diagram, the temperature and pressure at which all three phases can exist in equilibrium with one another.
For water triple point is
ºK or 0.01 ºC
Vapor pressure – pascals

81. For Water

82. A heating curve
Illustrates the changes of state as a solid is heated.
Uses sloped lines to show an increase in temperature.
Uses plateaus (flat lines) to indicate a change of state.

84. Learning Check A. A flat line on a heating curve represents
1) a temperature change
2) a constant temperature
3) a change of state
B. A sloped line on a heating curve represents

85. Solution A. A flat line on a heating curve represents
2) a constant temperature
3) a change of state
B. A sloped line on a heating curve represents
1) a temperature change

86. A cooling curve
Illustrates the changes of state as a gas is cooled.
Uses a sloped line to indicate a decrease in temperature.
Uses plateaus (flat lines) to indicate a change of state.

88. Learning Check Use the cooling curve for water to answer each.
A. Water condenses at a temperature of
1) 0°C 2) 50°C 3) 100°C
B. At a temperature of 0°C, liquid water
1) freezes 2) melts 3) changes to a gas
C. At 40 °C, water is a
1) solid 2) liquid 3) gas
D. When water freezes, heat is
1) removed 2) added

89. Solution Use the cooling curve for water to answer each.
A. Water condenses at a temperature of
3) 100°C
B. At a temperature of 0°C, liquid water
1) freezes
C. At 40 °C, water is a
2) liquid
D. When water freezes, heat is
1) removed