Condensation
change from vapor to liquid
Evaporation
state of changing from a liquid into a vapor (room temperature)
Vapor
a gas derived from a substance that is liquid at normal temperatures and pressures. It is also often used to describe gas that has recently come from a liquid
Rate of Evaporation
the number of particles moving from liquid to gas per second
Rate of Condensation
the number of particles moving rom gas to liquid per second
Dynamic Equilibrium
a state of balance between continuing processes/rates
Equilibrium vapor pressure
the partial pressure of vapor above a liquid in a closed system with a dynamic equilibrium between the rate of evaporation and the rate of condensation
Boiling
the conversion of liquid to vapor anywhere in the liquid rather than just at the top surface
Boiling Point temp
the temperature at which a liquid boils. (it is also the temperature at which the equilibrium vapor pressure of the liquid becomes equal to the external pressure acting on the liquid)
Normal Boiling Point
temperature at which the equilibrium vapor pressure of the liquid equals one atmosphere
Dipole
a molecule that contains an asymmetrical distribution of positive and negative charges
Dipole-dipole attraction
the intermolecular attraction between the partial negative end of one polar molecule and the partial positive end of another polar molecule
Electronegativity
a measure of the electron attracting ability of an atom in a chemical bond
Bond Dipole
a polar covalent bond, which has an atom with a partial positive charge and an atom with a partial negative charge
Intermolecular attraction
attraction between molecules
Hydrogen Bond
the intermolecular attraction between a nitrogen, oxygen, or fluorine atom of one molecule and a hydrogen atom bonded to a nitrogen, oxygen, or fluorine atom in another molecule
London dispersion forces
the attractions produced between molecules by instantaneous and induced dipoles
Metallic Bond
the attraction between the positive metal cations that form the fundamental structure of a solid medal and the negative charge from the mobile sea of electrons that surround the cations
Dispersion Forces/i.e. london forces
-weakest forces of attraction between molecules
-momentary dipole occurring due to uneven electron distributions
-weak residual attraction of the nuclei in one molecule for the electrons in a neighboring molecule
-more electrons that are present in the mo
Examples of molecules with dispersion forces
-Hydrogen (H2)
-Chlorine (Cl2)
-Carbon Dioxide (CO2)
-Dinitrogen Tetroxide (N2O4)
-Methane (CH4)
Dipole-Dipole interactions
-stronger than dispersion forces, yet not than hydrogen bonds
-occurs between molecules that have permanent net dipoles (polar molecules)
-partial positive charge on one molecule is electrostatically attracted to the partial negative charge on a neighbori
Examples of molecules with dipole-dipole interactions
-Sulfur DiChloride (SCl2)
-Phosphorus Trichloride (PCl3)
-Methyl Chloride (CH3Cl)
Hydrogen Bonds
-strongest because the hydrogen nucleus is extremely small and charged
-occurs between molecules that have a permanent net dipole resulting from hydrogen being covalently bonded to either fluorine, oxygen or nitrogen.
Examples of molecules with hydrogen bonds
-anything with fluorine, oxygen or nitrogen
Intermolecular forces
-between molecules
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-determines the physical properties of a compound and impact the chemical properties
intramolecular forces
-within molecules
-covalent bonds
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effect of a strong intermolecular force on boiling point
the stronger the intermolecular force, the higher the higher boiling point. this is because the molecules are closer together and it takes more to break them apart
gases
-total disorder
-lots of empty space
-particles have complete freedom of motion; particles are farther apart
cooling or compressing a gas
gas to liquid
heating or reducing pressure
liquid to gas
liquid
-disorder
-particles or clusters of particles are free to move relative to each other
-particles close together
cooling a liquid
liquid to solid
heating a liquid
solid to liquid
crystalline solid
-ordered arrangement
-particles are essentially in fixed positions
-particles close together
how can molecules without dipoles condense to form liquids or solids
slow the molecules down by cooling them and increasing the pressure
heating curve
-solid to gas
part 1 (A): temperature is being raised to break apart the IMF of a solid and make the molecules less together, like a liquid
part 2 (B): plateau, where the temperature is staying constant because all extra energy is used to break apart all
cooling curve
-gas to solid
part 1 (A): temperature is being lowered to gather the particles of the gas together so that it can start to form a liquid-like shape
part 2 (B): plateau, where the temperature is staying constant because all extra energy is using to bring a
freezing/melting (opposites)
freezing-liquid to solid
melting-solid to liquid
*at the plateaus
vaporization/condensation (opposites)
vaporization-liquid to gas
condensation-gas to liquid
*at the plateaus
why are changes in state considered to be physical changes and not chemical changes
no new substance is formed
why doesn't the temperature of a substance (such as ice) change during melting or freezing?
added energy is used to break intermolecular forces
what effect does the large molecular size have on the strength of intermolecular forces
larger the molecule, more dispersion forces you have
increased pressure
elevates the boiling point
decreased pressure
lowers the boiling point
molar heat of vaporization
heat energy required to vaporize one mole of a liquid at its standard boiling point
equilibrium
dynamic state in which two opposing changes occur at equal rates in the same system
what did farady do?
discovered it was possible to liquefy certain gases by cooling and compressing them
critical temperature
highest temperature at which it is possible to liquefy a gas
critical pressure
pressure required to liquefy a gas at its critical temperature
critical volume
volume occupied by one mole of gas under these conditions
sublimation
conversion of a solid directly into a gas
freezing point
temperature at which solid and liquid forms of a substance exist in equilibrium
phase change
conversion of a substance from one of the three physical states of matter to another
volatile
description of a liquid that evaporates easily
deposition
transformation of a gas directly into a solid (opposite of sublimation)
what average kinetic energy of particles in a liquid depends
temperature
reason for why solids do not flow
because the attractive forces between their particles are stronger than those in liquids or gases
when dynamic equilibrium is reached
when the rate of vaporization is equal to the rate of condensation
opposite of melting solid ice
freezing liquid
where can all three states of matter exist in equilibrium
triple point
why do ice cubes shrink and become rounded if left in the freezer for a long time
it sublimes
physical properties of liquids
-slight compressibility
-dense compared to gases
-non-definite shape
-slow rate of diffusion
physical properties of solids
-no compressibility
-very dense compared to gases
-definite shape
-does not diffuse
behavior of the molecules in a liquid in terms of intermolecular forces
there are weaker intermolecular forces than in solids, but stronger than in gases
how do intermolecular forces determine moelecular arrangement in solids
molecules held in fixed positions by strong attractive forces movement limited to vibrations
intermolecular forces determine on what properties
physical
intermolecular forces are forces of attraction between --
molecules
chemical bonds are forces between --
atoms
what are covalent bonds result rom
electrons being shared between atoms in a molecule
what do intermolecular forces result from
electron interactions between neighboring molecules
when the electron cloud is not distributed symmetrically, a molecule has --
dipole
all three types of chemical bonds
-ionic
-metallic
-covalent
types of intermolecular forces
-dispersion forces
-dipole dipole forces
-hydrogen forces
state of a substance at room temperature depends on
string of intermolecular forces
what are water molecules in an ice cube held together of?
intermolecular forces, i.e. hydrogen bonds
what type of force is between SO2 molecules
dipole dipole
force that accounts for HF being a liquid while H2 and F2 are gases
hydrogen bonding
force that depends on temperary, induced dipoles
dispersion forces
only intermolecular force that exists in noble gases
dispersion forces
attractive force between neighboring dipoles
dipole dipole
force that arises because of the large difference in electronegativities in the N-H bonds
hydrogen bonding
why does water have a unusually high boiling point?
-the molecules have a strong intermolecular force
-oxygen is more electronegative than hydrogen
-water is an angular molecule
-there is a large difference in electronegativity between oxygen and hydrogen
universal solid
water
why does a sample of boiling water remain at the same temperature until all the water has been boiled away
plateaus-all energy is being used to break apart intermolecular forces and once its changed to a different state, then temp rises again
changes in state physical or chemical?
physical
why does the boiling point of a liquid vary with altitude?
increased pressure elevates boiling point, reduced pressure reduces boiling point (higher the altitude, the higher the pressure)
conditions necessary for hydrogen bonding to exist in a substance or mixture
-bonded with something electronegative: N,O or F
why does vaporization require an input of energy
your breaking apart all intermolecular forces
how is the magnitude of a liquid's vapor pressure related to its intermolecular forces?
stronger the intermolecular force, lower the vapor pressure (harder to break apart)
bonding that exists in metals
metallic bonding (delocalized electrons)
alloys
mixture of a metal with another metal; 2 or more metals melted together
brass, jewelry, steel etc
lattice
the arrangement of particles in a crystal
unit cell
smallest part of a lattice
ionic crystal
-made up of both positive and negative ions that are arranged in a regular repeating pattern
-very hard and brittle
-high melting points and good conductors of electricity
ex: salt
covalent network cyrstal
-atoms that are covalently bonded to the atom next to them, meaning the two atoms share electrons
-hard and brittle, high melting points
-NOT conductors of electricity
ex: diamond
covalent molecular crystal
-made of covalently bonded molecules that are held together by intermolecular forces such as london dispersion forces dipole-dipole and hydrogen bonding
-soft, low melting points and good insulators
ex: ice crystal
metallic cyrstals
-made of metal cations surrounded by freely moving valence electrons
-electrons come from the metal atoms and belong to the crystal as a whole
-good conductors of electricity because the electrons are so mobile