1. Solids Definite shape and volume Vibrate around fixed positions
Crystalline (ordered arrangement)
Salt crystals
Shapes shown on periodic table
Amorphous (random arrangement)
Glass
Supercooled liquids  has liquid properties but appear to be solids

2. Liquids Definite volume, indefinite shape
More disorganized than solid but still fairly close together
Fluids  flow (both liquids and gases)
Surface tension-attraction between particles on surface
Paperclips float on water
Capillary action-attraction of liquid for a solid
Water in graduated cylinder attracted to glass forms a meniscus

3. Gases Assumptions of KMT for gases
1.large # of tiny particles take up practically no volume
2. Elastic collisions (no kinetic energy lost)
3. Continuous, rapid random motion
4. no forces of attraction
5. temperature depends on KE
KE = ½ mv2
Gasses likely to follow all assumptions:
Small nonpolar molecules
Normal or low pressure
Normal or high temp

4. Gases and Pressure Pressure caused by collisions Measuring pressure
Force per area
More collisions =more pressure
Smaller area = more pressure
Measuring pressure
Use barometer
Barometers used to be made of mercury

5. Force Pressure = Area Units of Pressure 1 pascal (Pa) = 1 N/m2
Barometer
Pressure =
Units of Pressure
1 pascal (Pa) = 1 N/m2
1 atm = 760 mm Hg=760 torr
= 101,325 Pa = kPa = bar
= 14.7 psi or lb/in2 = in. Hg

6. Converting between pressures
If your barometer reads 98 kPa, what is this pressure in atms?

8. Gases and Pressure Dalton’s Law of Partial Pressures
Total pressure is sum of partial pressures
PT = P1 + P2 + P3 + ….. (and so on)

9. Gases and Pressure Often gases are collected over water.
If we want to know the pressure of the dry gas you need to subtract the water vapor pressure
Appendix A-8 lists water vapor pressure
Pdry gas =Ptotal-PH2O

10. Gases and Pressure
If you know what percent of the mixture a gas makes up, it will exert that percent of the pressure.
Ex: a mixture of gases is made up of 50% Ar, 20% Xe, and 30% Kr. If the total pressure is 800 torr, what are the partial pressures?

12. The Gas Laws Show relationships between P (pressure) T (temperature
V (volume)
n (moles of gas)

13. The Gas Laws Boyle’s Law P1V1 = P2V2
↑Pressure = ↓volume (inverse relationship)
Other variable must be held constant (n, T)
P1V1 = P2V2
Example: If the pressure of a 250 mL aluminum can is raised from standard pressure to 4 atms, what will happen to the volume of the can? Temperature and moles are held constant.

14. How does Pressure and Volume of gases relate graphically?
Temperature,
# of particles
remain constant
Pressure

15. The Gas Laws Charles’s Law V1 = V2 T1 T2
↑temperature = ↑volume (directly proportional)
Constants (n, P)
V1 = V2
T T2

16. The Gas Laws Celcius must be changed to KELVIN K = 273 + °C Practice:
13 °C = ____K -10 °C = ____K
200K = ____ °C 0K = ______ °C

17. The Gas Laws
The temperature of a helium balloon is originally 20oC and has a volume of 600 mL, what will happen to the volume if the temperature drops to 5oC?

18. How does Temperature and Volume of gases relate graphically?
Pressure,
particles
remain constant
Temp

19. The Gas Laws Lussac’s Law P1 = P2 T1 T2
↑temperature = ↑pressure (directly proportional)
Constants (n, V)
P1 = P2
T T2

20. Gas Laws
What must the pressure be in a tire at 300K if the pressure is 20 psi at 275K?

21. How does Pressure and Temperature of gases relate graphically?
Volume,
# of particles
remain constant
Temp

22. Summary of the Named Gas-Laws:
RELAT-IONSHIP
CON-STANTS
Boyle’s
P V
P1V1 = P2V2
T, n
Charles’
V T
V1/T1 = V2/T2
P, n
Lussac’s
P T
P1/T1 = P2/T2
V, n

24. The Gas Laws Combined Gas Law P1 V1 = P2 V2 T1 T2
Puts other laws together
Relationship between P, V, and T
n still must be constant
P1 V1 = P2 V2
T1 T2

25. Example
A toy balloon has an internal pressure of 1.05 atm and a volume of 5.0 L at a temp of 20oC. What will happen to the volume when the pressure is 0.65 atm and temp. is -15oC?

26. Section 3 – Gas Volumes and the Ideal Gas Law
Avogadro’s Law
Equal volumes of gases at the same temperature and pressure contain equal number of molecules

27. Section 3 – Gas Volumes and the Ideal Gas Law
Molar Volume of a Gas
1 mol of gas at STP is 22.4 L (use for Stoichiometry )

28. Section 3 – Gas Volumes and the Ideal Gas Law
Molar Volume of a Gas
What volume does mol of gas occupy at STP?

29. Section 3 – Gas Volumes and the Ideal Gas Law
pV = nRT
R = Latm/molK

30. Section 3 – Gas Volumes and the Ideal Gas Law
What is the pressure in atm exerted by .5 mol sample of nitrogen gas in a 10.0 L container at 298 K?