States of Matter
I. Review: Phases of Matter
A. Solid
B. Liquid
C. Gas
II. Forces of Attraction
A. Intramolecular Forces
B. Intermolecular Forces
Short range forces between molecules
1. Hydrogen Bonding
- A particularly ______force
- Occurs in compounds in which a hydrogen atom is attached to ______, ______, or ______atom.
- The hydrogen atom will act like a ______
- The hydrogen atom will then be attracted to ______on a nearby molecule.
+ H O-
H+
+ H O-
H+
+ H O-
H+
- Hydrogen bonding ______melting and boiling points because ______energy is required to break the forces between molecules.
2. Dipole-Dipole Forces
- A ______force
- Occurs in ______molecules (dipoles) because they have ______charge distribution (a positive end and a negative end)
- ______end of one molecule is attracted to a ______end of a nearby molecule.
H+ - F --- H+ - F- --- H+ - F-
- Dipole – dipole forces will also ______melting and boiling points.
- A dipole can also temporarily attract electrons from another molecule causing an ______dipole.
3. London Dispersion Forces
- A ______intermolecular force (a type of induced dipole).
- Occurs in ______molecules and ______gases.
- Electrons are constantly ______, therefore electron density ______.
- This effect ______with increasing number of ______.
F2 Gas
Br2 Liquid
I2 Solid
III. Liquids and Solids
A. Liquids
1. Density and Compression
2. Fluidity
3. Viscosity
B. Solids
1. Density of Solids
2. Crystalline Solids
3. Network Covalent Solids
4. Metallic Solids
5. Amorphous Solid
IV. Gases and the Kinetic Molecular Theory
A. Kinetic Molecular Theory
B. Assumptions:
1. Particle Size
2. Particle Motion
a. Collisions
1. elastic
2. inelastic
b. Constant, rapid, random motion
In all directions
c. No forces of attraction or repulsion between gas particles
Therefore, do not stick together
3. Particle Energy
Depends on temperature
Increase Temp, Increase speed & KE of gas particles
Decrease Temp, Decrease speed & KE of gas particles
C. Temperature
1. Definition: A measure of the average KE of the particles in an object
2. Three scales:
a. Celsius – Anders Celsius, Swedish astronomer – Based on when water freezes and boils. (Δ 100o)
b. Kelvin – Lord Kelvin (William Thomson)
S.I. unit – Absolute zero – all motion stops (Δ 100o)
c. Fahrenheit – Gabriel Fahrenheit
Alcohol thermometer in 1709
Hg in 1714 (Δ 180o)
3. Conversions
K = oC + 273
oF = 1.8(oC)+32
oC = (oF-32)/1.8
4. Practice:
a. 28 o C = ______K
b. 200 K = ______o C
c. – 15 o C = ______o F
d. 10 K = ______o F
D. Physical Properties (of gases)
1. Density - low density à typically a small amout of mass per unit of volume
2. Fluidity
-Gases are more fluid than liquids
3. Compression
Reduce the volume by squeezing the molecules closer together
4. Expansion
-Increase volume, molecules move further apart
5. Diffusion
Movement of molecules. Mixingof gases – (high à low concentrations)
6. Effusion
Movement of molecules through a small opening (ex: puncture a tire or balloon)
E. Graham’s Law of Diffusion/Effusion
Velocity A √ Mass B
= at same T and P
Velocity B √ Mass A
Essentially, _Smaller__ molecules move _Faster_
than _larger_ ones.
Sample: Which gas will diffuse the fastest: ammonia, NH3, or hydrogen chloride, HCl?
F. Gas Pressure
1. Definition of Pressure:
Gas molecules hitting container walls
2. Mathematical Formula:
P = Force/area = N/m2 = Pascal (Pa)
3. Air Pressure Conversions-Conversion Factors
760 mmHg (torr) = 1 atm = 101.3 kPa = 30.0 in Hg = 1 torr = .133 kPa
Sample: Convert 0.70 atm to mmHg.
Practice:
Convert 2.0 atm to torr (mmHg).
Convert 725 torr to atm.
3. Atmospheric (air) Pressure
The mixture of gases surrounding the Earth exerting pressure (78%N2, 21%O2, Ar, CO2…)
4. Measuring Atmospheric Pressure
a. Hg Barometer = glass tube sealed at one end with the other end immersed in a container of Hg
5. Measuring Pressure of Gases
a. Closed Manometer
Instrument used to measure pressure of a gas in a closed container
b. Open Manometer
Open to air so that atmospheric pressure must be taken into account
5. Standard Pressure (STP = standard temperature and pressure (1 atm and 0oC)
1 Atm = 760 torr (mmHg)
6. Air Pressure Varies with Altitude
Higher altitudes = lower pressure
7. Dalton’s Law of Partial Pressures
Ptotal = P1 + P2 + P3 …….
The sum of all the individual pressures = the total pressure
Practice:
1. Determine the total pressure, in mm Hg, for a mixture that contains four gases with partial pressures of 5.0 atm, 4.56 atm, 3.02 atm, and 1.2 atm.
2. What is the partial pressure of hydrogen gas in a mixture of hydrogen and helium if the total pressure is 600 mmHg and the partial pressure of helium is 439 mmHg?
V. Phase Changes
A. Phase changes that require energy (endothermic)
1. Melting (fusion)
Solid to liquid
2. Vaporization (evaporation)
Liquid to gas
3. Sublimation
Solid to gas
B. Phase changes that release energy (exothermic)
1. Condensation
gas to liquid
2. Deposition
gas to solid
3. Freezing
liquid to solid
Heating Curve
Diagonal lines (1 state of matter) = inc in temp, inc in KE
Horizontal lines (2 states of matter) = Phase change
No change in temp, therefore, no change in KE