Exam 1 Flashcards
only compressible state of matter
gas
specific volume, but fill container
liquids
only state of matter that cannot diffuse
solids
specific shape & volume
solids
no specific volume - fills container
gases
3 things that cause change in state of matter
temperature
pressure
charge
determines state of matter
IMFs
define IMFs
short range attractive & repulsive forces between molecules
4 types of IMFs
- dipole-dipole interactions
- dispersion forces
- hydrogen bonds
- ion-dipole interactions
only non-van der waals IMF
ion-dipole
explain dipole-dipole
polar molecules - polarity caused by differences in electronegativity among atoms in molecule
partial charges result in a dipole
+ parts of molecule attracted to - parts of other molecules
examples of dipole dipole
H2O
HF
HCl
most electronegative parts of PT
top right
H
most electronegative element (4)
fluorine
____ and _____ of dipole dipole interactions determines properties
strength and number
strength of IMFs is reflected in….
BP
describe hydrogen bonding
subset of dipole-dipole interactions
includes H bound to N, O, or F
when H is bound to highly electronegative atoms, it acquires a highly positive charge & attracts other electronegative atoms
explain dispersion forces
result from instantaneous dipoles & induced dipoles
occur among ALL molecules
constantly happening
describe instantaneous dipole
nonuniform distribution of electrons (even in a nonpolar molecule)
temporary, moves back and forth
describe induced dipole
when an instantaneous dipole polarizes neighboring molecules
“pushes” electrons
_____ and _____ determines magnitude of dispersion forces
size & shape
which shape creates greater dispersion forces?
linear
more surface area
which molecules have largest instantaneous dipoles?
large
nonpolar
describe ion-dipole interactions
ions interacting with neutral polar molecules
examples of ion-dipole
salt dissolving in water (Na+ becomes surrounded by the O side of the water molecule, Cl- becomes surrounded by the H sides of the water molecule)
ammonia
acetic acid
magnitude of ion-dipole interactions depends on…
charge & size of ion
strongest ion-dipole interactions involve…
cations
highly charged ions
ions with smaller radii
define viscosity
resistance to flow
what increases viscosity?
IMFs
larger surface area
lower temp
higher molecular weight
define surface tension
measure of elastic force on surface of a liquid
what is the cause of surface tension?
the surface molecules are the only ones that do not have IMFs in all directions; because nothing attracts them from the top, they cohere to molecules below the surface
example of surface tension
capillary action
define vapor pressure
pressure exerted by a liquid’s vapor when the liquid and the vapor are in dynamic equilibrium
define volatile
liquids that evaporate more readily
volatile liquids have ______ IMFs and __ VP
weaker IMFs
higher VP
higher temperature _______ VP
increases
define boiling point
temperature at which a liquid’s VP equals external pressure acting on liquid’s surface
define normal BP
BP at 1 atm (760 torr)
properties of solids are based on…
how molecules are held together
define melting point
temperature at which energies of individual particles allow them to break free of their fixed positions
regular repeating arrangement
crystalline solids
arrangement lacks regularity
amorphous solids
well-defined MP
crystalline solids
MP varies
amorphous solids
define unit cell
smallest repeating structure in a crystal
where two lines meet on a unit cell
lattice point
7 types of unit cells
- Simple cubic
- Tetragonal
- Orthorhombic
- Rhombohedral
- Monoclinic
- Triclinic
- Hexagonal
primitive cubic
total atoms
L =
1 atom
L = 2r
V =
V = L3
body-centered cubic
total atoms
L =
2 atoms
L = 4r/√3
face-centered cubic
total atoms
L =
4 atoms
L = √8(r)
define coordination number
how many particles one particle touches
body centered CN
8
face centered CN
12
5 steps to find density of a unit cell
- find number of atoms
- find total mass (in units requested)
- find length of the unit cell (in units requested)
- find volume
- find density
corner atom = ___ of an atom
1/8
edge atom = ___ of an atom
¼
face atom = ___ of an atom
½
1 AMU = _______ grams
1 AMU = 1.66*10-24 grams
1 gram = ________ AMU
1 gram = 6.022*1023 AMU
how to convert from pm to cm
L (in pm) * 1 m/1012 pm * 100 cm/1 m = L (in cm)
D =
D = m/v
cations & anions held together by Coulumic attraction
ionic crystals
ionic crystal properties (5)
hard, brittle, high MP, poor conductor, often white/grainlike
large network of atoms connected by covalent bonds
covalent crystals
diamonds, graphite, silicon dioxide, silicon carbide
covalent crystals
covalent crystal properties (4)
hard, brittle, high MP, poor conductor
repeating structures held together by van der waals forces (hydrogen bonds, dispersion, dipole-dipole)
molecular crystals
sugar, ice, dry ice, caffeine
molecular crystals
molecular crystal properties (3)
soft, low MP, poor conductors
crystals likely to be organic
molecular
held together by van der waals forces - electrons are delocalized & shared
metallic crystals
metallic crystals properties (4)
strong, malleable, good conductors, variable MPs
4 types of crystals
ionic
covalent
molecular
metallic
