Chapter 10 Flashcards
Dipole-Dipole Forces
Attraction between molecules with dipole moments
The larger the difference in electromagnetic, what happens to dipole moment?
increases in size
Inter-molecular Forces
Forces that exist between the molecules/atoms that a substance is composed of
What bonds are INTRAMOLECULAR?
ionic and covalent bonding
Dipole-Dipole forces are considered?
uneven, polar, and weak
Dipole Dipole force interactions maximize what between the atoms?
attractive forces
Dipole Dipole force interactions minimize what between the atoms?
repulsive forces
Dipole dipole forces compared to ionic solids?
1% as strong
Dipole Dipole forces only exist in what phases?
solid and liquid
Hydrogen bonding is what strength?
strong
Hydrogen bonding is a specific example of?
Dipole-Dipole attraction
Hydrogen bonding is only between?
hydrogen and oxygen, fluorine, nitrogen
What gives water its unique properties?
hydrogen bonding
London dispersion forces are considered?
non-polar and most weak
In London dispersion forces what are formed?
instantaneous dipoles
Molecules without dipole moments still need to have?
ability to exert force on one another
instantaneous dipoles exist in?
non-polar molecules and diatomic gases
The random movement of electrons can create?
non-symmetrical electron distribution
Instantaneous dipoles can induce?
short lived dipole in neighboring molecules
London dispersion forces exist between all molecules but are?
the weakest forces of attraction
Polarizability
how easy the electron cloud of an atom can be distorted to give a dipole charge
Polarizability increases with?
the number of electrons in a molecule
the more electrons a molecule has the more chances for?
a momentary dipole interaction to occur
CCl₄ experiences greater London dispersion forces than?
CH₄
Surface tension
the resistance of a liquid to an increase in its surface area
Which shape has the smallest surface area?
sphere
the higher the intermolcular forces, the greater?
the surface tension can be
Have higher surface tensions in liquid state?
polar substances
Capillary action
based upon cohesive forces between liquid molecules
Adhesive forces are between?
polar liquid molecules and polar bonds in the material and the container
glass has partial negative charges and attracted to?
positive end of polar molecules
Waters adhesive forces are greater than
cohesive forces
cohesive forces
the force of attraction between the same molecules
adhesive forces
forces between the liquid molecules and their container
what in glass is attracted to hydrogen in water?
oxygen
Viscosity
resistance to flow
structural models for a liquid are dependent on? (3)
-Intermolecular forces
-polar or nonpolar
-what adding to liquid
Is there a definite model for liquids?
no
Crystalline solids have a highly ______ arrangement of components?
regular
The components of a crystalline solid arrange themselves how?
3D lattice network that is repeated throughout the structure
Unit Cell
smallest repeating 3D lattice
a solid can be composed of?
atoms, ions, or molecules
The type of component found at the lattice point determines?
what type of solid that you are
Types of solids
molecular, ionic, atomic
What type of solid has the lowest melting point?
molecular
What type of solid has lowest enthalpy of fusion?
molecular
Order of weakest to strongest attractive forces?
molecular, ionic, metallic, network covalent
Amorphous solid
Components are “frozen in place” before they can achieve an ordered arrangement
What do amorphous solids lack?
ordered arrangement
examples of amorphous solids?
glass and plastic
Ionic solids are composed of?
hard, high melting point, conduct when dissolved in water
In ionic solids ions occupy?
lattice points
Molecular solids
discrete covalent bonded molecules at each lattice points
lattice point
a point at the intersection of grid lines in a regularly spaced array of points
examples of molecular solids
ice and sucrose
3 subgroups of atomic solids?
metallic, network, group 8A
network solids
atomic solids with strong directional covalent bonds
closet packing
arrangement of packing uniform hard spheres into the most efficient use of available space
spheres are arranged in?
layers
each sphere is surrounded by?
6 others
In the second layer, how are the spheres arranged?
to fill in the dimples formed by three spheres in the first layer
In the 3rd layer what are the two ways the particles can arrange themselves?
aba, abc
hexagonal closest packing
has hexagonal unit cell structure
In hexagonal closest packing each layer is?
identical
In hexagonal closest packing the spheres in _____ occupy the same ________?
every other level, vertical positional
Aba is also known as?
hexagonal closest packing
Hexagonal closest packing abbreviated is?
hcp packing
Cubic Closest Packing
has a face centered cubic unit cell
Cubic Closest Packing is also referred to as?
ccp
In Cubic Closest Packing the spheres in every _____ layer occupy the same ________.
4th, vertical position
What is common in both ccp and hcp?
-12 equivalent nearest neighbors
-6 in the same layer
-3 in layer above
-3 in layer below
Where does an intermolecular force occur?
between molecules
changes in state of matter are due to ___________ among the molecules rather than those ________ the molecules.
changes in force, within
how much energy is needed to vaporize 1 mole of water?
40.7 kJ
how much energy is needed to break the O-H bond in 1 mole of water molecules?
934 kJ
dipole moment
molecules with polar bonds behaving as if they had a center of positive and negative charge.
as the distance between the dipoles increases, the force of attraction?
weakens
the formation of a temporary dipole can affect?
electron distribution of a neighboring atom
Instantaneous dipole
The separation of charges in a non-polar molecule at an instant due to sudden disturbance in the electron cloud around the molecule
The formation of a temporary dipole is also called?
instantaneous dipole
the instantaneous dipole that occurs accidentally can induce?
a similar dipole in a neighboring atom
Why does the freezing point rise as you go down group 18?
increased polarizability
To increase a liquid’s surface area, molecules must?
move from the interior to the surface
Which liquids have relatively large intermolecular forces?
polar molecules
Liquids with large intermolecular forces tend to have high?
surface tensions
When do adhesive forces occur?
When a container is made of a substance with polar bonds
The concave shape of a meniscus shows water’s ___________ are greater than _______.
adhesive forces, cohesive forces
liquids with large intermolcular forces tend to be?
highly viscous
When does a convex meniscus occur?
when a liquid has stronger cohesive forces than adhesive forces.
Crystalline Solids
highly regular arrangement of components
lattice
3D system of points designating the position of substances that make up a substance
The structure of crystalline solids are most commonly determined by?
x-ray diffraction
atomic solids include?
carbon, boron, silicon and all metals
Two types of alloys
substitutional and interstitial
electron sea model
explains how metals can conduct electricity and are malleable and ductile
In electron sea model where are metal cations found?
in a “sea” of valence electrons
The valance electrons found in the electron sea model are?
mobile
The mobile electrons in the electron sea model can?
conduct heat and electricity
The metal ions in the electron sea model can be easily moved around as?
metal is hammered into a sheet or pulled into a wire
Alloy
substance that contains a mixture of elements and has metallic properties
What happens in a substitutional alloy?
some of the host metals are replaced by other metal atoms of similar size
What happens in a interstitial alloy?
holes in closest packed metal structure are occupied by small atoms
Network solids are composed of?
brittle, do not efficiently conduct heat or electricity.
Two most common forms of carbon?
diamond and graphite
diamond and graphite are?
network solids
The differences in diamond and graphite arise from?
differences in bonding
silica is composed of?
oxygen, quartz, and some types of sand
silicates are found in most?
rocks, soils, and clays
O/Si ratio
2:1
Silicates O/Si ratio is?
greater than 2:1
Silicates contain?
silicon-oxygen anions
When silica is heated above its melting point and cooled rapidly what happens?
an amorphous solid called glass results
Silicon is a ___________ element
semiconducting
how can the conductivity of silicon be enhanced at normal temperature?
doping the silicon crystal with certain other elements
When molecules have dipole moments, their intermolecular forces are?
significantly greater, especially when hydrogen bonding is possible
Ionic solids are ________, ____________ substances
stable, high melting
how are ionic solids held together?
by strong electrostatic forces that exist between oppositely charged ions
Three types of holes in closet packing structures?
Trigonal, tetrahedral, octahedral
Trigonal holes
formed by 3 spheres in same layer
Tetrahedral holes
formed when a sphere sits in the dimple of 3 spheres in an adjacent layer
octahedral holes
formed between two sets of three spheres in adjoining layers
example of substitutional alloy
brass
example of interstitial alloy
steel
by adding smaller atoms to a interstitial alloy, you alter?
the properties of the host metal
diamonds are composed entirely of?
carbon-60
each carbon in a diamond is?
surrounded by a tetrahedral arrangement of other carbon atoms
network solids can be viewed as?
giant molecules
the structure of diamond is held together and stabilized with?
covalent bonds that are formed by the overlap of sp3 hybrid orbitals
Why is diamond a poor conductor of heat but a good insulator?
Because of large gap between the occupied and unoccupied orbitals
graphite is made of?
carbon-10
Graphite is a great conductor of?
electricity
The structure of graphite is based on?
layers of carbon atoms in 6 member rings
Each carbon in one layer is surrounded by?
3 other carbons in a trigonal planar arrangement with sp2 hybridization
There are what kind of bonds in graphite’s layers?
pie bonds
Pie bonds in graphite contribute to?
stablization and conductivity because of delocalized electrons associated with them.
In graphite there are ______ bonds within the layers and ____ between the layers.
strong, weak
The more London dispersion forces the _________ the boiling point?
higher
In non-metals, metallic bonds are present in?
aluminum foil and copper wire
What solid has valance electrons delocalized over huge array of atoms?
network solids
Vaporization or evaporation is clear evidence that?
the molecules of a liquid can escape the liquid’s surface and form a gas
What type of process is vaporization?
endothermic
Why is vaporization endothermic?
energy is required to overcome the strong intermolecular forces in the liquid
heat of vaporization
the energy required to vaporize 1 mole of a liquid at a pressure of 1 atm.
Heat of vaporization is also called?
enthalpy of vaporization
Condensation
the process by which vapor molecules reform into a liquid
A system is a equilibrium when no further net charges occur in?
the amount of liquid or vapor
In any closed container at equilibrium, the rate of condensation and vaporization
exactly balance each other out
Equilibrium Vapor Pressure
the pressure of the vapor present at equilibrium
Equilibrium Vapor Pressure is also called?
vapor pressure
Silicon is different from carbon because?
it cannot use 3p orbitals to form pie bonds with oxygen due to its large size
The silica structure has all ___ bonds?
single
Why does silica have only single bonds?
silica cannot form a double bond with oxygen
quartz is based on a?
SiO4 tetrahedron
Silica is the main component of _____ which is an amorphous solid.
glass
Molecular solids can be though of as?
one giant molecule
In molecular solids what takes place within the molecules?
strong covalent bonding
In molecular solids what takes place between the molecules?
weak attractive forces
Examples of molecular solids
Ice, Dry Ice, S8
Generally the attractive forces between the molecules in molecular solids are?
London Dispersion
What happens to the London dispersion forces in a molecular solid as the size of the molecules increase?
increase in strength
Vapor Pressure is very dynamic on the molecular level because?
molecules are constantly escaping and entering the liquid phase
Why is equilibrium established in a closed container?
because molecules are constantly escaping and entering the liquid phase
Once vapor pressure is ______kPa or ________atm or _____mmHg that is boiling point.
101.3, 1, 760
Lower vapor pressure means ____ ______ _______ in liquids.
greater intermolecular forces
High vapor pressure means ____ _______ _______ in liquids.
lower intermolecular forces
Why do liquids with greater intermolecular forces have low vapor pressures?
the significant attractions between the molecules need to be overcome before the liquid particles can move into the gas phase
Sublimation
substance goes from solid to gas phase.
Reasons for sublimation
-solids have low vapor pressures
-solids with little intermolecular attraction are able to sublime at room temperatures
heat of fusion
energy required to co convert 1 mole of solid substance into a mole of liquid substance
Normal melting point
temperature at which the solid and liquid states have same vapor pressure under 1 atm
Normal boiling point
temperature at which the vapor pressure of a liquid is exactly 1 atm
Super cooling
liquid is cooled below 0 degrees Celsius and remains in a liquid state
In super cooling the quick temperature change does not allow time for?
the organization of the molecules into an orderly solid structure
Super heating
when a liquid is heated above its boiling point
How is super heating avoided in lab?
boiling chips
In super heating, there is not enough _____ _____ _______ accumulated in one place to form bubbles and escape.
high energy molecules
Most slopes in a closed diagram have?
positive slope between liquid and solid
The water in a closed diagram has a _______ slope between the _____ & _______ phase.
negative, solid, liquid
What occurs at triple point?
-solids and liquids have identical vapor pressure
-all three phases exist together in equilibrium
Critical Temperature
temperature where substances can not exist as a liquid no matter the pressure.
Critical Pressure
the pressure needed to produce a liquid at critical temperature
Critical point
point where critical temp and critical pressure meet
Melting Point ____ as pressure increases for water.
decreases
Why does Melting point decreases as pressure increases for water?
the density of ice is less than that of water thus the volume increases.
