1. Warm up (left side)
Define each type of intermolecular force below and state what type of molecule you would find this force.
dipole-dipole –
London dispersion force –
Hydrogen – bonding –

2. Left side activity
Compare and contrast the molecular views of a substance as a solid, liquid, and gas, including the intermolecular forces.

3. Gas Laws

4. Physical Characteristics of Gases
Contents
Kinetic Molecular Theory
Define pressure & units
Gas Laws with relationship between pressure, temperature, volume, and quantity of gases.

5. Kinetic Molecular Theory
The kinetic molecular theory is based on the idea that particles of matter are always in motion. The theory provides a model of an ideal gas.
ideal gas = imaginary gas that perfectly fits all the assumptions of the kinetic molecular theory.

6. 5 Assumptions of kinetic molecular theory
1. Gases made of tiny particles far apart relative to their size.
2. Collisions between gas particles and between particles and container walls are elastic collisions.
elastic collisions = one in which there is no net loss of kinetic energy
3. Gas particles are in continuous random motion.

7. Thus, the smaller mass particles-have higher velocity.
4. There are no forces of attraction or repulsion between gas particles.
5. The average kinetic energy of gas particles depends on the temperature of the gas.
KE = ½mv2
m=mass
v=velocity
All gases at the same temperature have the same average kinetic energy.
Thus, the smaller mass particles-have higher velocity.
**Gases behave like ideal gases if the pressure is not very high or the temperature is not very low.**
Examples:#4 diffuison
Ex. Diffusion, size of gas molecules and speed

8. Properties of Real Gases real gas = a gas that does not behave according to the assumptions of the kinetic molecular theory
1. no definite shape or no definite volume
2. expands to fill the container
3. low density
4. compressible
5. exhibits diffusion and effusion
diffusion = spreading out of particles from high concentration to low
effusion = process that particles pass through a small opening

9. Kinetic molecular theory will hold true for real gases if the pressure is not very high and the temperature is not very low. Plus nonpolar gases will hold closer to the kinetic theory than polar gases.
Which gases would deviate significantly from the kinetic molecular theory?
He, O2, H2, H20, N2, HCl, NH3?
H20, HCl, NH3 (Polar gases)
To describe a gas, 4 measurements must be stated:
volume, temperature, pressure, number of gas particles

10. Pressure & Units pressure = force per area pressure = force area
newton = SI unit of force
1N = 1kg.m/s2
Units of pressure
Standard pressure = pressure at sea level and 0oC
1 atmosphere = kilopascals = 760millimeters of Hg = 760 torr
1 atm =101.3 kPa =760 mm of Hg = 760 torr
Pressure is measured by a barometer or manometer.

11. STP STP = standard temperature and pressure
temperature = average kinetic energy of the particles
Standard temperature = OoC or 273 K
Convert the following: 35 oC = ___________ K
231 K _______ oC

12. Pressure conversion problems
Convert the following
0.830 atm = _____________ mm of Hg
.830 atm X mm of Hg = 631 mm of Hg
atm
98.1 kPa = ______________ torr
98.1kPa X torr = 736 torr
kPa
755 mm of Hg = ____________ kPa
755 mm of Hg X kPa = kPa
mm of Hg

13. Open Manometer
An open manometer is filed with mercury and connected to a container of hydrogen. The mercury level is 62 mm higher in the arm of the tube connected to the gas. Atmospheric pressure is 97.7 kPa. What is the pressure of the hydrogen in kilopascals?
62 mm X kPa = 8.3 kPa
mm of Hg
97.7 kPa
-8.3 kPa
89.4 kPa

14. Closed Manometer
A closed manometer is connected to a container of nitrogen. The difference in the height of mercury in the two arms is 691 mm. What is the pressure of the nitrogen in kilopascals?
691 mm of Hg X kPa = 92.1 kPa
mm of Hg

15. Video Demonstration: Gas Laws
Bozeman Ideal gas

16. Robert Boyle
Theologian
Physicist
Alchemist

17. Boyle’s Law
PV = k

18. Boyle’s Law Boyle’s Law (temperature constant) P1V1 = P2V2
A balloon filled with helium gas has a volume of 500 mL at a pressure of 1 atm. The balloon is released and reaches an altitude of 6.5 km, where the pressure is 0.5 atm. Assuming that the temperature has remained the same, what volume does the gas occupy at this height?
A gas has a pressure of 1.26 atm and occupies a volume of 7.40 L. If the gas is compressed to a volume of 2.93 L, what will its pressure be, assuming constant temperature?
Divers know that the pressure exerted by the water increases about 100 kPa with every 10.2 m of depth. This means that at 10.2 m below the surface, the pressure is 201 kPa; at 20.4m, the pressure is 301 kPa; and so forth. Given that the volume of a balloon is 3.5 L at STP and that the temperature of the water remains the same, what is the volume 51 m below the water’s surface?

19. Solution to Boyle’s Law
mL X 1 atm = V2 X 0.5 atm
1000 mL = V2
L X 1.26 atm = 2.93 L X P2
3.18 atm = P2
100 kPa = P2
10.2 m
5 x 102 kPa
101.3 kPa (atmospheric pressure)
kPa
600 kPa
3.5 L X kPa = V2 X 600 kPa
0.6 L = V2

20. Jacques Alexandre Cesare Charles 1746-1823
Balloonist
Invented hygrometer

21. Charles’ Law
V = k’T

22. Charles’s Law Answer to Problems 2.75L = 2.46L 293.0 K T2
T2 = 262 K = -11oC
L = L
338K T2
T2 = X 102K = 37.0oC
Charles’s Law (pressure is constant)
V1 = V2
T T2
Temperature must be in Kelvin!!
A helium-filled balloon has a volume of 2.75 L at 20.0oC. The volume of the balloon decreases to 2.46 L after it is placed outside on a cold day. What is the outside temperature in K? In oC?
A gas at 65oC occupies 4.22 L. At what Celsius temperature will the volume be 3.87 L, assuming the same pressure?

23. Joseph Louis Gay-Lussac 1778-1850
Coined pipette and burette
1808 discovered boron
1802 formulated Charles’ Law

24. Gay-Lussac’s Law
P = k’’T

25. Avogadro’s Law
V = k’’’n

26. Gay Lussac’s Law Gay Lussac’s Law (volume is constant) P1 = P2 T1 T2
Before a trip from New York to Boston, the pressure in an automobile tire is 1.8 atm at 20oC. At the end of the trip, the pressure gauge reads 1.9 atm. What is the Celsius temperature of the air inside the tire? (Assume tires with constant volume.)
1.8 atm = atm T2 = 309 K = 36oC
293 K T2
At 120.0oC, the pressure of a sample of nitrogen is 1.07 atm. What will the pressure be at 205oC, assuming constant volume?
1.07 atm = P P2 = 1.30 atm
393k K
A sample of helium gas has a pressure of 1.20 atm at 22oC. At what Celsius temperature will the helium reach a pressure of 2.00 atm ?
1.20 atm = atm T2 = 492 K = 219oC
295K T2

27. 4 Laws combined together
PV = k
V = k’T
P = k’’T
V = k’’’n
To give PV =nRT Ideal Gas Relationship

28. PV = nRT P is pressure (atmospheres) V is volume (liters) n is moles
T is temperature (Kelvins)
R is the gas constant ( L atm/mol K)

29. Example 1
What is the volume of 1.00 mol of a gas at 0oC and 1.00 atm pressure?
PV = nRT
P = 1.00 atm
T = oC = 273 K
n = 1.00 mol
V =
1.00 x x 273
= 22.4 L
1.00

30. Combined Gas Law P1V1 = P2V2 T1 T2
The volume of a gas is 27.5 mL at 22.0oC and atm. What will the volume be at 15.0oC and atm?
2. A mL gas sample of at STP is compressed to a volume of mL, and the temperature is increased to 30.0oC. What is the new pressure of the gas in kPa?
Solution
.974 atm mL = .993atm . V2
295K K
V2 = 26.3 mL
101.3kPa mL = P mL
273 K K
P2 = 394 kPa