1. CHEM 121 Chapter 7
Winter 2015

2. States of Matter
Matter:
Physical states:
Properties of Matter:

3. Solids Strong attractive forces ( ) Properties:
_________________ density
_________________ compressibility
_________________ shape
_________________ thermal expansion

4. Liquids Medium forces ( ) Properties: _________________ density
_________________ compressibility
_________________ shape
_________________ thermal expansion

5. Gases No attractive forces High kinetic E: Properties:
_________________ density
_________________ compressibility
_________________ shape
_________________ thermal expansion

6. Units of Pressure Millimeter of mercury atmosphere
psi, pounds per square inch (engineering)
pascal
atmosphere

7. Gas Laws
4 Variables: P: T: V: n:

8. Boyle’s Law
volume occupied by a gas is __________ related to its pressure

9. 3-minute practice
A sample of gas has a volume of mL at 1.0 atm. If we increase the pressure to 2.0 atm, what is the new volume of the gas (T is constant)?

10. Charles’s Law
volume of a gas is __________ related to its temperature (K)

11. 3-minute practice
A sample of gas has a volume of mL at 27 ˚C. If we heat the gas to 54 ˚C (keeping P constant), what is the new volume of the gas?

12. Gay-Lussac’s Law Combined Gas Law:
At constant volume, pressure is __________ related to temperature
Combined Gas Law:

13. Avogadro’s Law At fixed T & P: equal volumes of any ideal gas have…
The volume occupied by a gas is __________ proportional to the amount (mol) of gas (fixed T & P)
At fixed T & P:
equal volumes of any ideal gas have…

14. Gas Behavior at STP
STP:
Standard Molar Volume

15. 3-minute practice
What is the volume (mL) of 0.10 g of helium gas at STP?

16. Ideal Gas Law Combine: Solve at STP… Boyle’s Law Charles’s Law
Avogadro’s Law
Solve at STP…

17. A tank filled with methane at 23 ˚C and 0
A tank filled with methane at 23 ˚C and atm is fitted with a safety valve that opens if internal pressure exceeds 1.00 x 103 torr. When the tank is placed in boiling water at exactly 100. ˚C, will the safety valve open?

18. A sample of gas occupies 105 mL at 0. 903 atm
A sample of gas occupies 105 mL at atm. If temperature remains constant, what is the volume (in L) at 26.4 kPa?

19. Mixtures of Gases
Each gas in a mixture acts like it is the only gas present
Dalton’s Law of Partial Pressures:
Example: When water vapor added to pure air….
Each gas exerts __________________________________

20. Changes of State
Intermolecular Forces:

21. Intermolecular Forces
dipole-dipole
polar molecules acting like magnets
if between H and
N, O, or F
_______________ H O H H O O H H H
All intermolecular forces are weaker than bonds (ionic, covalent, metallic)
London Dispersion forces

22. Vapor Pressure As a liquid evaporates: Vapor Pressure:
But if closed container…
Stronger intermolecular forces  lower vap pressure
Vapor Pressure:

23. Boiling As you increase T, vapor pressure _____________
If vapor pressure reaches atmospheric pressure…

24. Sublimation and Melting
Solids have vapor pressures too!
Typically low or high?
Sublimation:
Melting:
Decomposition:

25. Heating and Cooling Curves
Plateaus:
Slopes:

26. Changes of State Equations
Heat of Fusion:
Heat of fusion for water = 80 cal / g
Heat of Vaporization:
Heat of vaporization for water = 540 cal / g