1. Chapter 7 Gases, Liquids, & Solids Appearance by Intermolecular Forces

2. The Nature of Gases Indefinite shape and indefinite volume
expand to fill their containers
compressible
Fluid – they flow
Low density
1/1000 the density of the equivalent liquid or solid

3. Pressure
Is caused by the collisions of molecules with the walls of a container
Is equal to force/unit area
P=F/A
SI units = Newton/meter2 = 1Pascal (Pa)
101,325 Pa = 1 standard atmosphere (1atm)
1 atm = 760mmHg = 760 torr = 14.7 psi

6. GAS LAWS Boyle’s Law Charles’ Law Gay-Lussac’s Law Avogadro’sLaw
Ideal Gas Law
Daltons Law

7. The Relationship Between Pressure and Volume
BOYLE’S LAW
The Relationship Between Pressure and Volume

8. Robert Boyle ( )
Boyle was born into an aristocratic Irish family
Became interested in medicine and the new science of Galileo and studied chemistry. 
A founder and an influential fellow of the Royal Society of London
Wrote prolifically on science, philosophy, and theology.

9. Boyle’s Law
Boyle’s Law: The volume of a gas is inversely proportional to the pressure applied to the gas when the temperature is kept constant.
Decrease in volume = Increase in pressure.
Increase in volume = Decrease the pressure

11. Boyle’s Equation: P1V1 = P2V2 Therefore: V1=(P2V2)/P1 V2= (P1V1)/P2
P1=(P2V2)/V1
P2=(P1V1)/V2

12. You have a 2L cylinder of gas that is under 100 kPa of pressure
You have a 2L cylinder of gas that is under 100 kPa of pressure. If you compress the gas to 1L, what will the new pressure be?
You have a 10.0L container of gas under 505 torr of pressure. If you increase the pressure to 1155 torr, what will the new volume be?
Problems

13. The Relationship Between Temperature and Volume

14. Jaques Charles ( )
Charles studied the compressibility of gases nearly a century after Boyle
French Physicist
Conducted the first scientific balloon flight in 1783

15. Charles’ Law
At a fixed pressure, the volume of a gas is proportional to the temperature of the gas.
As the temperature increases, the volume increases.
As the temperature decreases, the volume decreases.

17. How Did He Figure It Out?
A cylinder with a piston and a gas is immersed in a water bath.
A mass is placed on top of the piston which results in a pressure on the gas. This mass is held constant, which means that the pressure on the gas is constant.
The gas volume is measured as the temperature is increased and V vs. T data point plotted. This is continued over a large range of temperatures.

18. Charles’ Equation
Rearrange the equation to solve for V1, T1, V2, or T2
V1=(V2T1)/T2
T1=(V1T2)/V2
V2=(V1T2)/T1
T2=(V2T1)/V1
All temperatures must be in KELVIN!!!

19. A cylinder contains 5. 00L of gas at 225K
A cylinder contains 5.00L of gas at 225K. If the temperature is increased to 345K, what will the new volume be?
A tire contains 2.00L of air at 300.0K, if the volume in the tire decreased to 1.50L, what must the new temperature be?
A ball contains 3.00L of air at 32.0ºF, if the volume increases to 5.00L, what must the temperature have changed to?
Problems

20. The Relationship Between Pressure and Temperature
Gay-Lussac’s Law
The Relationship Between Pressure and Temperature

21. Joseph Louis Gay-Lussac 1778 - 1850
French chemist and physicist
Known for his studies on the physical properties of gases.
In 1804 he made balloon ascensions to study magnetic forces and to observe the composition and temperature of the air at different altitudes

22. Gay-Lussac’s Law
The pressure of a fixed amount of gas at fixed volume is directly proportional to its temperature in Kelvin.
As the temperature increases, the pressure also increases
As the temperature decreases, the pressure also decreases

24. Gay-Lussac’s Law Expressed Mathematically as:
Rearranging this equation to solve for the variables gives us:
P1=(P2T1)/T2
P2=(P1T2)/T1
T1=(P1T2)/P2
T2=(P2T1)/P1
All temperatures must be in KELVIN!!!

25. Jim Bob (he’s back) has revved his engine enough so that the internal temperature and pressure of his engine are 700.0K and 200.0kPa. If the temperature outside was 295K before Jim-Bob got into his car, what was the internal pressure in his engine?
Today, the barometer reads 750mmHg and the thermometer says that it is 65ºF. At 6am, the barometer read 700mmHg, what was the temperature at that time?
Problems

26. The Relationship Between Pressure, Volume, and Temperature
The Combined Gas Law
The Relationship Between Pressure, Volume, and Temperature

27. The Combined Gas Law
A combination of Boyle’s, Charles’, and Gay-Lussac’s laws.
Temperature must be in KELVIN.

28. Rearranged to solve for each variable:
P1=(P2V2T1)/(V1T2)
V1=(P2V2T1)/(P1T2)
T1=(P1V1T2)/(P2V2)
P2=(P1V1T2)/(V2T1)
V2=(P1V1T2)/(P2T1)
T2=(P2V2T1)/(P1V1)

29. Problems
Rhonda’s helium balloon has a volume of 2.00L at 2.00atm and 395K. If the temperature is raised to 500.K and the gas is compressed to 1.00L, what is the new pressure?
Ryan ate at Taco Shack last night. He now has gas which takes up 1.29L of bowel space under 2.35atm of pressure at 310K (body temp). What will be the volume of Jeremy’s gas after he expels it if the atmospheric temperature and pressure are 75ºF and 1.00atm respectively?

30. Avogadro’s Law The Relationship Between Pressure, Temperature, Volume and Moles

31. Amedeo Avogadro (1776-1856) Italian physicist and mathematician
Born in a noble ancient family of Piedmont
“Avogadro’s Number” is named after him
6.022 x 1023
The number of things in a mole

32. Avogadro’s Law
One mole of any gas occupies exactly 22.4 liters (dm3) at STP.
STP = Standard Temperature and Pressure
Temp = 0ºC = 273K
Pressure = 1atm = 760 mmHg = 760 torr etc.
This is often referred to as the “molar volume” of a gas.

33. Equal volumes of gases, at the same temperature and pressure, contain the same number of particles, or molecules.
Thus, the number of molecules in a specific volume of gas is independent of the size or mass of the gas molecules.

35. Avogadro’s Law Where “n” is the number of moles of gas present
Mini Version: “At STP”

37. Luis has 3.5 mol of H2 gas at STP. What volume will this gas occupy?
Joann has a balloon of CO2 gas that contains mol CO2 at 1atm and 273K. If Joann let half of the gas out, what would the new volume be?
Problems

38. The Ideal Gas Law

39. For a static situation (not a final and initial situation) you can relate the pressure, volume, moles, and temperature of a gas
PV=nRT
Rearranging the equation gives us:
P = (nRT)/V
V = (nRT)/P
n = (PV)/(RT)
T = (PV)/(nR)
All temperatures must be in KELVIN!!!
Ideal Gas Law

40. The Universal Gas Constant
R is the Universal Gas Constant
Depending on the units of pressure or volume, the R value will be different
R = L x atm x K-1 x mol-1
R = L x torr x K-1 x mol-1
R = L x mmHg x K-1 x mol-1
R = L x kPa x K-1 x mol-1
Make sure to match and cancel out the right units

41. Problems
Rosy has a 5.0L tank of H2 gas. If the pressure inside the tank is 800.0torr and the temperature is 300.0K, how many moles of hydrogen does her tank contain?
Chris’ favorite meal is a bean and cheese burrito from Del Taco. Unfortunately, this means that his intestines were filled with moles of CH4 gas under 2atm of pressure. What is the volume of gas that occupies his bowels? *Make an assumption about Temp*

42. Dalton’s Law The Law of Partial Pressures

43. John Dalton (1766-1844) English Chemist and Physicist
Did much research on color blindness
He was colorblind
Famous for his atomic theory
Worked with gases

44. Dalton’s Law: The total pressure exerted by a mixture of gases is the sum of the individual pressures of each gas in the mixture
Dalton’s Equation:

45. Problems
The air in this room contains the gases shown below at their respective partial pressures in kPa. What is the pressure your body feels from the air in this room?

46. What is the pressure in problem 1 if you convert it to atm? Torr? mmHg?
3) Scuba Divers use gas mixtures of O2 and He. If the diver to your right breathes in a mixture that has a total pressure of 6.5 atm and a partial pressure from O2 of 1.2 atm, what is the partial pressure of He?

47. Liquids Particles close, but far apart enough to allow for movement
Slide passed each other
Fluid
Definite volume
No definite shape
High density
Low compressibility
Low thermal expansion

48. Solids Atoms very close Definite shape Definite volume High Density
Very small thermal expansion

49. Intermolecular forces
Dispersion forces
Dipole-dipole
Hydrogen bonding
Ionic bonds

50. 1) Dispersion forces Also called London forces or van der Waals forces
Caused by momentary dipoles in atoms or otherwise non-polar molecules
Effect is often seen in very large molecules

52. 2) Dipole-Dipole Attractions
Attraction between two polar molecules
Positive end of one molecule is attracted to the negative end of another molecule

53. 3) Hydrogen bonding Special dipole-dipole attraction
Occurs between the H that is bonded to a very electronegative atom (O, N, F) on one molecule and the lone pair(s) on a very electronegative atom on another molecule
Surface tension

55. 4) Ionic bonds Occur between ions Usually a metal and a non-metal
Hold ions close together
Require large amounts of energy to break
Example: M.P. of NaCl = 801°C

56. Interaction
Relative Strength
Ionic
1000
Hydrogen Bond
100
Dipole-Dipole 10
Dispersion 1

57. Identify the major intermolecular force for the following molecules
Cl2
NH3
C10H22 KI
HBr
Practice

58. Change of State
a.k.a. freezing

60. Substance
M.P. (°C)
B.P. (°C)
H2O
100 Au
1064
2856
CH4
-182.5
-161.6
NaCl
801
1465

61. Chapter 7 checklist Nature of gases Pressure
Boyles, Charles, Gay-Lussacs, Combined, Avogadros, Ideal gas laws.
STP- standard temperature and pressure, 273 K, 1 atm, 1 mole gas = 22.4L
Daltons law
Intermolecular Forces – ionic bonds, dipol-dipole, hydrogen-bonding, london dispersion
Know relative strengths!!