1. Unit 7 States of matter and the Behavior of Gases
Chemistry
Chapter 13 & 14

2. Goal 1: States of Matter and Vocabulary
Attractive Forces
Forces between particles of a substance. Intermolecular Forces. Hold particles together.
Kinetic Energy
Energy of Motion. Related to mass and speed of particles
KE = ½ mv2
Temperature
Measure of Average Kinetic Energy of a sample. As temperature increases, particles move faster in a sample
Collisions
Collisions between atoms and molecules are ELASTIC. This means Kinetic Energy is conserved. TEMPERATURE is NOT lost due to Collisions. Collisions result in PRESSURE.

3. States of Matter SOLID LIQUID GAS Attractive Forces between Particles
Strong
Weaker
Virtually Nonexistent
Volume & Compressibility
Definite Volume
Not Compressible
Indefinite Volume
Compressible
Molecular Motion
Low
Small distance between
Medium
High
Large distance between

5. Goal 2: Kinetic Molecular Theory
Describes the MOTION of gas particles
3 Statements of the Theory
The particles in a gas are considered to be small, hard spheres with an insignificant volume:
NO attractive or repulsive forces exist between them.
The particles of a gas travel in rapid, constant, and random motion. They travel in straight line paths that are independent of each other.
All collisions between particles are perfectly elastic (no kinetic energy is lost). The total kinetic energy of the gas particles remains constant.

6. Kinetic Molecular Theory helps explain PRESSURE, VOLUME, and TEMPERATURE.
Gas Pressure
Number of collisions that take place. More collisions = More pressure.

7. Kinetic Molecular Theory helps explain PRESSURE, VOLUME, and TEMPERATURE.
Number of collisions that take place. More collisions = More pressure.
Volume
Space that particles take up. Particles will completely fill a container with their random motion.

8. Kinetic Energy and Temperature
Kinetic Molecular Theory helps explain PRESSURE, VOLUME, and TEMPERATURE.
Pressure
Number of collisions that take place. More collisions = More pressure.
Volume
Space that particles take up. Particles will completely fill a container with their random motion.
Kinetic Energy and Temperature
Average Kinetic Energy of Particles
Related to speed of particles. Greater Speed = Greater Temperature.

9. Kinetic Molecular Theory Simulations

10. Temperature Theory: Kelvin Scale
Volume
Temperature
What is absolute 0?
How was 0K found?
Why use Kelvin?

11. The Nature of Liquids Goal 3: Attractive Force Affects

12. Vapor Pressure
The pressure caused by evaporated gas particles pushing down upon a liquid
Stronger attractive forces result in lower Vapor pressures
At higher temperatures vapor pressure increases
More molecules evaporate at higher temperatures
Water: Low vapor pressure
Chart on page 427(WATER)
Temp. V. Pressure
20°C 2.33kPa
60°C kPa
100°C kPa

13. Vapor pressure of substance

14. Boiling Point
Temperature at which vapor pressure equals external pressure.
The liquid goes beyond just evaporation at Boiling Point.
Gas bubbles begin to form throughout the liquid.
Stronger attractive forces result in higher BP’s

15. Volatility Likelihood of a liquid evaporating.
High Volatility: Liquid has high vapor pressure
Liquid is more likely to evaporate – produce more vapor
High Volatility: Liquids with weaker attractive forces
Water: Low volatility

16. Surface Tension Inward force (pull) between the molecules of a liquid.
High Surface Tension: Holds a liquid into drops
Liquids with very strong attractive forces have greater surface tension
Water: High surface tension

17. Goal 4: Phase Diagrams Triple Point Page 438“Phase Diagram
Temperature and Pressure in which ALL THREE phases can exist.
Page 438“Phase Diagram

18. Goal 5: Gas Variables 4 variables define a gas system Pressure: (P)
Units:
Pascal (Pa)
Atmospheres (atm)
Millimeters of Mercury (mm Hg)
1 atm = kPa = 760 mm Hg
Volume: (V)
Liters (L), milliliters (mL), (cm3)
Temperature: (T)
Celsius (°C)
Kevin (K)
Kelvin is the Official Unit
Kelvin must be used in calculations
Number of Particles: (n)
Unit:
Moles (mol)

19. Stoichiometry Review At STP: 1mol = 22.4L Review
STP: Standard Temperature and Pressure
1 atm (101.3 kPa)
0°C (273 K)
Review
1 mol = molar mass
1 mol = 6.02 x 1023 particles
1 mol = 22.4L (at STP)

20. Stoichiometry Examples
Li3N(g) H2O(l)  NH3(g) LiOH(aq)
What mass of water is needed to react with 29.3 L of Li3N?
When 13.3 L of NH3 are produced how many formula units of LiOH are produced?
Given 7.8 moles of LiOH produced, what volume of Li3N was used?

21. Math Review Direct Relationship (between X & Y)
Generic Equation
Y = kX (k is a constant)
k = Y/X
Graph
Y vs. X will be a LINE (k is the SLOPE)
Inverse Relationship (between X & Y)
Y = k/X (k is a constant)
k = XY
Y vs. X will be a HYPERBOLA

22. Goal 6: Gas Laws

23. Boyle’s Law At constant TEMPERATURE: Pressure and Volume are INVERSE
PV = constant
P1V1 = P2V2
Graph of P vs. V:
As Pressure increases  Volume ___________

24. Boyle’s Law At constant TEMPERATURE: Pressure and Volume are INVERSE
PV = constant
P1V1 = P2V2
Graph of P vs. V:
As Pressure increases  Volume _decreases _

25. Sample Problem 14.1
A balloon contains 30.0 L of helium has at 103 kPa. What is the volume of the helium when the balloon rises to an altitude where the pressure is only 25.0 kPa? (Assume that the temperature remains constant

26. Charles’ Law At constant PRESSURE: Temperature and Volume are DIRECT
V/T = constant
Graph of V vs. T:
As Temperature increases  Volume __________

27. Charles’ Law At constant PRESSURE: Temperature and Volume are DIRECT
V/T = constant
Graph of V vs. T:
As Temperature increases  Volume _increases_

28. Sample Problem 14.2
A balloon inflated in a room at 24⁰C has a volume of 4.00 L. The balloon is then heated to a temperature of 58⁰C. What is the new volume if the pressure remains the same?

29. Gay-Lussac’s Law At constant VOLUME:
Temperature and Pressure are DIRECT
P/T = constant
Graph of P vs. T:
As Temperature increases  Pressure _________

30. Gay-Lussac’s Law At constant VOLUME:
Temperature and Pressure are DIRECT
P/T = constant
Graph of P vs. T:
As Temperature increases  Pressure increases_

31. Sample Problem 14.3
Aerosol cans carry labels warning not to incinerate (burn) the cans or store them above a certain temperature. This problem will show why it is dangerous to dispose of aerosol cans in a fire. The gas in a used aerosol can is at a pressure of 103 kPa at 25⁰C. If the can is thrown onto a fire, what will the pressure be when the temperature reaches 928⁰/C?

32. Combined Gas Law
All 3 laws put together
k = constant

33. Sample Problem 14.4
The volume of a gas-filled balloon is 30.0 L at 313 K and 153 kPa pressure. What would the volume be at STP?

34. Gas Law Simulations

35. Ideal Gas Law P: Pressure V: Volume T: Temperature n: Number of Molesor
P: Pressure
V: Volume
T: Temperature
n: Number of Moles
R: Ideal Gas Law CONSTANT
R = 8.31 (kPa∙L)/(K∙mol)

36. Sample Problem 14.5
At 34⁰C, the pressure inside a nitrogen-filled tennis ball with a volume of L is 212 kPa. How many moles of nitrogen gas are in the tennis ball?

37. Special Problem:
What is the volume of 1 mol of a gas at STP?

38. Goal 7: Dalton’s Law
The total pressure of a gas mixture is the “sum” of the pressures of each individual gas in the mixture
Pt = P1+P2+P3…
Each gas pressure depends on its abundance
Mole Fraction or Abundance
“think percent as decimal”

39. Atmosphere
TOTAL
NITROGEN
78%
OXYGEN
21%
OTHERS 1%
If total pressure is 1 atm and they all have the same volume, calculate each partial pressure:
Nitrogen’s Pressure = (.78)(1 atm) = .78 atm
Oxygen’s Pressure = (.21)(1 atm) = .21 atm
Others Pressure = (.01)(1 atm) = .01 atm

40. Dalton Law Examples
A container has a mixture of atmosphere and water vapor. At 50°C the partial pressure of water vapor is kPa. What is the pressure of the atmosphere gasses if the total pressure is kPa?
A container contains 10 g of oxygen gas, 80 g of nitrogen gas and 1 g of carbon dioxide. The total pressure of the container is kPa, find:
Mole fraction of each gas
The partial pressure of each gas

41. Graham’s Law
The velocity of particles is related to their temperature (ave. Kinetic Energy) and their mass. Simulation
KE = ½ mv2
Therefore v =
v is inversely proportional to the mass of the particle at any given temperature.
For 2 gases (A and B)

42. Graham’s Law Applications
At the SAME TEMPERAURE
Molecules with smaller masses have greater velocities
molecules with greater masses have smaller velocities
DIFFUSION:
The tendency of molecules to move toward areas of lower concentration.
Molecules with greater velocities have greater rates of diffusion
2 effects on Diffusion rates:
1) Temperature: Higher temp = higher rate
DIRECT
2) Mass: Smaller mass = higher rate
INVERSE