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Terms in this set (47)
What is the fundemental difference between the states of matter?
the distance between particles
solids and liquids (particles are close together)
What determines that state of matter at a particular temperature and pressure?
The kinetic energy of the particles and
The strength of the attractions between the particles
more kinetic energy than attractive force then its a
more attraction that kinetic force then its a
solid or liquid
forces of attraction between molecules
Which are stronger intramolecular forces or intermolecular forces?
What do intermolecular forces determine?
They control physical properties such as boiling and melting points, vapor pressures, and viscosities.
London dispersion forces
temporary attractive force between temporary dipole moments in neighboring or adjacent atoms
How are London dispersion forces formed?
Sometimes electrons will end up on one side of a molecule, creating a temporary dipole -> this induces another dipole on a neighboring molecule -> this creates an attraction
attractions between an instantaneous dipole (the dipole creating when the first atom randomly had an uneven distribution of electrons) and an induced dipole (the dipole created when atoms nearby were impacted by the first).
True or False: London dispersion forces are present in all molecules regardless of polarity
the ease with which the electron distribution in the atom or molecule can be distorted
Comparing the strength of london dispersion forces
1. shape of the molecule: long, skinny molecules -> tend to have stronger dispersion forces than short, fat ones bc of increased surface area in n-pentane.
2. Molecular weight: increases with more molecular weight; Larger atoms have larger electron clouds, which are easier to polarize.
Boiling pt _______ are molecular weight increases
Molecules that have permanent dipoles are attracted to each other
How do dipole-dipole forces work?
The positive end of one is attracted to the negative end of the other and vice-versa.
Comparing dipole-dipole forces
strength of dipole (greatest difference in electronegativity values)
True or false: dipole-dipole interactions are only important when the molecules are close to each other.
The more polar the molecule
the higher the boiling pt (ask question about diagram)
Hydrogen from one molecule is attracted to an electronegative element (F, O, N) in another molecule
How does hydrogen bonding work?
when hydrogen is bonded to one of those very electronegative elements, the hydrogen nucleus is exposed (positive attractive charge) making it possible to bond with a negative charge on a different molecule
an attractive force that results from the electrostatic attraction between an ion and a neutral molecule that has a dipole (ask about these)
ion-dipole interactions are important force in
solutions of ions bc the strength of these forces are what make it possible for ionic substances to dissolve in polar solvents.
A liquid's resistance to flowing (the ease at which molecules can move past each other)
Viscosity ___________ with stronger intermolecular forces and ___________ with higher temperature.
if partciles are strongly attracted to eachother, they can flow past each other easily
Stronger intermolecular forces means _________ viscocity
a measure of the elastic force on the surface of a liquid (creates an invisible barrier or a film)
ASK WHAT IT HAS TO DO WITH INTERMOLECULER FORcES
What is surface tension caused by?
cohesive forces between the same type of molecule on the surface of a liquid.
All molecules in the liquid are attracted toward themselves, so those on the surface are attracted downwards and sideways (not upwards).
the ability for a substance to draw itself upwards against gravity in a small tube.
How capillary action works
relies on cohesive and adhesive forces (ability to attach two different surfaces). The smaller the tube the more surface (in comparison to the volume of the substance) there is for the liquid to attract towards.
As surface area increases, capillary action _________
Stronger intermolecular forces have ____________ capillary action
a measure of the pressure (force per unit area) exerted by a gas above a liquid in a sealed container.
How does vapor pressure work?
1. partially filled container of liquid is sealed
2. Some liquid molecules at surface evaporate
3. The vapor molecules cannot escape
4. After some time, the space above the liquid reaches a point where it cannot hold any more vapor molecules.
5. vapor molecules condense back into a liquid.
The system reaches the point where the rate of evaporation is equal to the rate of condensation.
the vapor molecules above the surface of the liquid exert a pressure on the walls of the container.
A liquid with weak intermolecular forces evaporates more easily and has a ________ vapor pressure.
A liquid with stronger intermolecular forces does not evaporate easily and thus has a _________ vapor pressure.
an increase in temperature causes an increase in vapor pressure because
more molecules have entered the gas phase.
When the liquid in a closed container is heated, more molecules escape the liquid phase and evaporate.
The greater number of vapor molecules strike the container walls more frequently, resulting in an increase in pressure.
the temperature at which its vapor pressure equals atmospheric pressure.
normal boiling point
the temperature at which its vapor pressure is 760 torr (standard!)
heat of fusion
Energy required to change a solid at its melting point to a liquid.
Heat of vaporization
The amount of energy required for the liquid at its boiling point to become a gas
The heat (energy) added to the system at the melting and boiling points goes into
pulling the molecules farther apart from each other
True or false: The temperature of the substance does rise during the phase change
false; , it only splits the intermolecular forces
display the state of a substance at various pressures and temperatures and the places where equilibria exist between phases (transitions occur between two phases)
review phase diagram
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