AP Chem-Unit 3 (1-4)

Inter molecular forces

The forces holding solids and liquids together

• much weaker than bonds
  -when substance melts/boils -- are broken

Ion-Dipole Forces

Interaction between ion and dipole
Strongest of all intermolecular forces

Dipole Dipole Forces

Exist between neutral polar molecules
Weaker than ion dipole
If two molecules have about the same mass and size, the dipole-dipole forces increase with increasing polarity

London Dispersion Forces

Weakest of all the forces, exist between all molecules
One molecule's electron cloud can become distorted causing an instantaneous dipole and that can induce another instantaneous dipole in an adjacent molecule/atom
Forces between instantaneous dipoles are ---
The strength of the LDF depends on how polarizable an atom or molecule is, more polarizable ->stronger LDF

More Polarizable Molecules…

1. Greater size (more electrons)
2. Shape (more electrons exposed, flatter)
3. The existence of pi bonds

Hydrogen Bonding

Special case of Dipole Dipole forces
H-F, H-O, H-N boiling points are extremely high --> intermolecular forces are high
Requires:
H bonded to a small, highly EN element (F,O,&N)
an unshared electron pair on a nearby small, highly EN ion or atom

Ionic Solids

• -- Bond
• High MP
• Brittle and Hard
• Relatively Dense
• Dull Surface
• Conducts elec when melted or dissolved
• Ions

Molecular Solids

• Van der Waals forces
• Low MP
• Soft
• Low Density
• Dull Surface
• Cannot conduct electricity
  -Atoms or molecules

Covalent Network Solids

• --- Bond
• High MP
• Very Brittle and Hard
• Low Density
• Dull Surface
• Cannot conduct electricity
  Atoms in networks

Metallic Solids

• Atoms
• MP depends on e- configuration
• Ductile and Malleable and Very Hard
• Usually High Density
• Lustrous (Shiny)
• Can conduct electricity

Amorphous

No pattern to the arrangement of particles. Their
melting point is over a wide range of temperatures. They just get
softer and softer when heated. (Examples- glass, plastic, wax)

Crystalline

Well-ordered, definite arrangement of atoms.
Crystals have a repeated structure and a melting point at a very
narrow range of temperatures. (Examples- metals, H2O, diamond)

Endothermic

melting, evaporating/boiling & sublimation

Exothermic

freezing, condensation, & deposition

Critical Temp

min temp required for a substance to become supercritical fluid

Critical Pressure

minimum pressure required to become super critical fluid

Triple Point

All 3 phases of matter at equilibrium

heat of vaporization

the heat energy required to evaporate a given mass of liquid at a constant temp

heat of fusion

the heat energy required to melt a given mass of a solid at a constant temperature

viscosity

resistance of a liquid

• thicker the liquid the more viscosity
• the stronger the IMF, higher ---
• as temp increases --- decreases

Surface Tension

Acts as thin skin
Bulk molecules (those in liquid) are equally attracted to their neighbors. Surface molecules are only attracted inwards towards the bulk molecules. Surface molecules are packed more closely.
--- is the amount of energy required to increase surface area of a liquid

• Stronger IMF, greater ---

Dynamic Equilibrium

the point when as many
molecules escape the surface
as strike the surface.

Vapor Pressure

is the
pressure exerted when the
liquid and vapor are in
dynamic equilibrium.

Liquids boil when…

the external pressure equals the vapor pressure.

Normal Boiling Point

is the boiling point at
760 mmHg (1 atm).

Volitile

A substance with a
high vapor pressure is
said to be ---. It
readily evaporates.

Pressure

force acting on an object per unit area P= F/A

Manometer

The pressures of gases not
open to the atmosphere are
measured in ---.

A --- consists of a
bulb of gas attached to a
U-tube containing Hg.

Avogadro's Hypothesis

equal volumes of gas at the
same temperature and pressure will contain the same
number of molecules.

Avogadro's Law

the volume of gas at a given
temperature and pressure is directly proportional to the
number of moles of gas.

Doubling the moles of gas in a balloon would double the
volume of a balloon.

STP

0 C or 273.15 K
1 atm or 760 mmHg or 101.3 kPa

Density equals

nM/V or PM/RT (no more varun or please manage roy's things)

Molar Mass equals

dRT/P (dirt pump)

Partial Pressure equals

X(specific mol/total mols)*P(total)