1. Describe the differences between various states of matter

2. Ch. 10 Physical Characteristics of Gases
10.1 Kinetic Molecular Theory

3. The Kinetic Molecular Theory
based on the idea that particles are constantly moving
can be applied to solid, liquid, or gas
provides a model of ideal gas behavior so only an approximation

4. Gases consist of tiny particles that are very far apart
most volume is empty space-low density
allows gases to be easily compressed
All collisions between particles and container walls are elastic
there is no net loss of energy when particles collide
total kinetic energy stays constant even though it can be transferred between particles

5. Particles are in continuous, rapid, random motion
since they are moving, they have KE
KE overcomes their attractive forces
No forces of attraction or repulsion
like billiard balls
bounce apart immediately

6. Average kinetic energy depends on temperature
KE increases as temperature increases
KE = ½mv2
where m = mass of particle
where v = velocity of particle
so at the same T, lighter particles have higher speeds than heavier ones
velocity and temperature are directly proportional

7. Real vs. Ideal Gases ideal gas is defined by the KMT
most gases behave close to the ideal when
high temperature – so they have enough KE to overcome attractive forces
low pressure – so they are very spread out
Gases with little attraction are more ideal (monatomic gases)

8. Ch. 10 Physical Characteristics of Gases
10.2 Pressure

9. Pressure P : force per unit area on a surface
Newton – SI unit for force (1 kg*m/s2)
why would shoes with smaller diameter heel not be allowed on gym floor?
As surface area decreases, pressure increases
Pressure exerted by a gas depends on
volume
temperature
number of molecules

10. Measuring Pressure barometer
instrument used to measure atmospheric pressure
first one created by Torricelli in early 1600s
glass tube filled with mercury is inverted in a dish
mercury flows out of the tube until pressure of the Hg inside the tube is equal to the atmospheric pressure on the Hg in the dish

11. Measuring Pressure manometer: measures pressure of gas in a container
gas has less pressure than atmosphere if the Hg is closer to chamber
gas has more pressure than atmosphere if the Hg is further from chamber

12. Units of Pressure millimeters of mercury (mmHg) torr (torr)
from mercury barometer
torr (torr)
from Toricelli inventing barometer
atmosphere of pressure (atm)
Pascal (Pa) = 1N/m2 (SI unit)
named after French scientist
1 atm = 760 mmHg = 760 torr = kPa

13. Practice Conversions
Convert atm to
mmHg
torr
kPa

14. Practice Conversions
Convert kPa to
atm
mmHg
torr

15. The pressure of a gas is measured as 49 torr
The pressure of a gas is measured as 49 torr. Convert this pressure to atmospheres, kiloPascals, and mmHg.

16. Pressure Conversions
The pressure of a gas is measured as 49 torr. Represent this pressure in atmospheres, Pascals, and mmHg.

17. Ch. 10: Physical Properties of Gases
10.3 Gas Laws:
Relationships between volume, temperature, pressure, and amount of gas.

18. Boyle’s Law: P and V as one increases, the other decreases
inversely proportional
pressure is caused by moving molecules hitting container walls
If V is decreased and the # of molecules stays constant, there will be more molecules hitting the walls per unit

19. Boyle’s Law: P and V
Boyle’s Law: the V of fixed mass of gas varies inversely with P at a constant T.
PV = k
k is a constant for a certain sample of gas that depends on the mass of gas and T
What kind of graph is V vs. P?
If we have a set of new conditions for the same sample of gas, they will have same k so:

20. Boyle’s Law

21. Boyle’s Law: P and V Discovered by Irish chemist, Robert Boyle
Used a J-shaped tube to experiment with varying pressures in multistory home and effects on volume of enclosed gas

22. Example: Boyle’s Law
Consider a 1.53-L sample of gaseous SO2 at a pressure of 5.6 x 103 Pa. If the pressure is changed to 1.5 x 104 Pa at constant temperature, what will be the new volume of the gas?

23. Charles’ Law: V and T if P is constant, gases expand when heated
when T increases, gas molecules move faster and collide with the walls more often and with greater force
to keep the P constant, the V must increase

24. Charles’ Law: V and T
Problem: if we use Celsius, we could end up with negative values from calculations in gas laws for volumes
we need a T system with no negative values: Kelvin Temperature Scale
starts at ° C = absolute zero = 0 K
lowest possible temperature
balloon going into liquid nitrogen

25. Charles’ Law: V and T
Charles’ Law: the V of fixed mass of gas at constant P varies directly with Kelvin T.
V = kT
k is a constant for a certain sample of gas that depends on the mass of gas and P
What kind of graph is V vs. T?
If we have a set of new conditions for the same sample of gas, they will have same k so:

26. Charles’ Law discovered by French physicist, Jacques Charles in 1787
first person to fill balloon with hydrogen gas and make solo balloon flight

27. Example: Charles’ Law & Temp.
A sample of gas at 15°C and 1 atm has a volume of 2.58 L. What volume will this gas occupy at 38°C and 1 atm?

28. A weather balloon is released at a pressure of 744 mmHg with a volume of 12 L. What will the volume be at a pressure of 704 torr?

29. Ch. 10: Physical Properties of Gases
10.3 Gas Laws:
Relationships between volume, temperature, pressure, and amount of gas.

30. Gay-Lussac’s Law: P and T
Remember:
P is the result of collisions of molecules with container walls
Force and frequency of collisions depends on average KE
KE depends on T
If the T increases, collisions occur more often and with higher force so the P must increase

31. Gay-Lussac’s Law: P and T
Gay-Lussac’s Law: the P of fixed mass of gas at constant V varies directly with Kelvin T.
P = kT
k is a constant for a certain sample of gas that depends on the mass of gas and V
What kind of graph is P vs. T?
If we have a set of new conditions for the same sample of gas, they will have same k so:

32. Gay-Lussac’s Law
discovered in 1802 by Joseph Gay-Lussac

33. Example: Gay-Lussac’s Law
The gas in an aerosol can is at a pressure of 3.00 atm at 25°C. Directions on the can warn the user not to keep the can in a place where temperature exceeds 52°C. What would the gas pressure be in the can at 52°C?

34. How to Remember which law goes with each pair of variables:
Boyle’s
P V T
Gay-Lussac’s
Charles’

35. Ch. 10 Physical Characteristics of Gases
10.3b Combined Gas Law

36. Combined Gas Law a gas often changes in T, P, and V all at once
the other gas laws can be combined into one law
Combined Gas Law- relationship between P, V, and T of a fixed amount of gas

37. Example: Combined Gas Law
A Helium-filled balloon has volume of 50.0 L at 25°C and 1.08 atm. What volume will it have at atm and 10.°C?

38. Example
A balloon containing 5.5 L of air at 25C and 755 torr is put at the bottom of the ocean. The new temperature is 4 C and the new volume is 2300 mL. What is the new pressure?

39. Ch. 10 Physical Characteristics of Gases
10.4 Dalton’s Law of Partial Pressure

40. Dalton’s Law of Partial Pressure
John Dalton
responsible for atomic theory
also studied gas mixtures
the P of gas mixture is the sum of the individual pressures of each gas alone
the P that each gas exerts in the mixture is independent of the P that are exerted by other gases

41. Dalton’s Law of Partial Pressure
the total P of a mixture of gases is equal to the sum of partial P of component gases, no matter how many different gases
PT = P1 + P2 + P3 + …
Partial Pressure- P of each gas in mixture

42. Why?
the particles of each gas in a mixture have an equal chance to hit the walls
so each gas exerts P independent of that exerted by other gases
total P is result of the total # of collisions per unit of wall area

43. Water Displacement
gas produced is less dense than water so it replaces the water in the bottle
gas collected is not pure because it contains vapor from the water
PT = Pgas + Pwater
set for a certain T
equal to atmospheric pressure

44. Example
Oxygen gas from decomposition of KClO3 was collected by water displacement. The barometric pressure and the temperature during the experiment were torr and 20.0°C respectively. If the partial pressure of water vapor is 17.5 torr at 20.0°C. What was the partial pressure of oxygen collected?
PT = PO2 + PH2O
731.0 torr = PO
PO2 = torr

45. Example
Find the partial pressure by 2 gases (A and B) mixed if the overall pressure is 790 mmHg. The percent by volume is A: 20% and B: 80%.
PT = PA + PB = 790 mmHg
A: 0.20 x 790 = 158 mmHg
B: 0.80 x 790 = 632 mmHg