CHEM 121
Chapter 7
Winter 2014
1
Kinetic Molecular Theory of Matter
Explains matter in various states
1.
2.
3.
4.
5.
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
Measuring Pressure
Pressure (P)
Barometer:
http://encarta.msn.com/media_461532488_
761573986_1_1/mercury_barometer.html
7
Units of Pressure
• pascal
•
•
• atmosphere
•
• Millimeter of mercury
•
•
• psi, pounds per square inch
(engineering)
1 atm  760 mmHg
8
Gas Laws
4 Variables:
P:
T:
•
V:
n:
9
Boyle’s Law
volume occupied by a gas is __________ related to its pressure
10
3-minute practice
A sample of gas has a volume of 100.0 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)?
11
Charles’s Law
volume of a gas is __________ related to its temperature (K)
12
3-minute practice
A sample of gas has a volume of 100.0 mL at
27 ˚C. If we heat the gas to 54 ˚C
(keeping P constant), what is the new
volume of the gas?
13
Gay-Lussac’s Law
At constant volume, pressure is __________ related
to temperature
Combined Gas Law:
14
Avogadro’s Law
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…
•
•
15
Gas Behavior at STP
• STP:
•
•
• Standard Molar Volume
16
3-minute practice
What is the volume (mL) of 0.10 g of
helium gas at STP?
17
Ideal Gas Law
Combine:
– Boyle’s Law
– Charles’s Law
– Avogadro’s Law
Solve at STP…
18
A tank filled with methane at 23 ˚C and 0.991 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?
Initial:
T=
P=
n=
V=
Final:
T=
P=
n=
V=
19
A sample of gas occupies 105 mL at 0.903 atm. If temperature
remains constant, what is the volume (in L) at 26.4 kPa?
Initial:
P=
V=
n=
T=
Final:
P=
V=
n=
T=
20
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 __________________________________
21
Graham’s Law
• Effusion: gas leak through hole
• Diffusion: spontaneous mixing of gases
rateA

rateB
molecular mass B
molecular mass A
22
3-minute practice
Which will deflate more quickly:
a balloon filled with helium or nitrogen?
23
Changes of State
Intermolecular Forces:
24
Intermolecular Forces
• dipole-dipole
• polar molecules acting
H
like magnets
O
• if between H and
N, O, or F
_______________
H
H
O
H
O
H
H
• London Dispersion forces
•
•
25
Vapor Pressure
As a liquid evaporates:
•
•
• But if closed container…
Vapor Pressure:
26
Boiling
• As you increase T, vapor pressure _____________
• If vapor pressure reaches atmospheric pressure…
27
Sublimation and Melting
Solids have vapor pressures too!
– Typically low or high?
Sublimation:
Melting:
Decomposition:
28
Heating and Cooling Curves
• Plateaus:
• Slopes:
29
Specific Heat (SH)
Amount of heat to raise the T of ___ of a substance by ____
How much energy is needed to raise the temperature of 20.0 g
of iron by 14.5 °C?
30
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
31
Solid State
32
Solid State
33