Chapter 10 Flashcards
(37 cards)
IMF
Inter molecular forces
-Forces of attraction
- Gas-weak
- Liquide-Moderate
- Solid-Strong
Intramolecular Force
Those that hold the atoms together within the molecule (covalent bonds)
Intermolecular forces
attractions between molecules
Three types of intermolecular forces in Pure substances
- London dispersion force
Dispersion Force
-Are present in all atoms & molecules
-Even molecules with no net dipole moment with have fluctuations in the electron distribution that result in an instantaneous or transient dipole moment
-As a transient dipole is established in one molecule it induces a dipole in all the surrounding molecules
-Induced dipoles cause attractive forces: dispersion forces
Strength of intermolecular forces
Can be measured by boiling point
Polarizability:
The ease with which the electron cloud can be distorted by neighboring charges
Dipole-Dipole Forces
- Only occur between polar molecules (with fixed net dipoles)
Dominates when comparing molecules of similar size
But for molecules of very different sizes, dispersion forces dominate-will probably not give us a question on it
Hydrogen Bonding
-Only if an H bonded to F,O, & N
-Very electronegative atoms is bonded with H is strongly pulls the bonding electrons toward it
- The H nucleus becomes exposed, acts as a very strong center of positive charge
-If another molecule has a F, O, N it will have a strong parctial negative charge
Format X-H-Y
X & Y must be F,O, or N
Dispersion Forces
the weakest, present in all molecules
✓Increase with increasing molar mass
✓Can be significant in large molecules
Higher boiling point for stronger forces
Ion-dipole forces
An attractive force that results from the electrostatic attraction between an ion and a neutral molecule that has a dipole.
There will be questions on ranking boiling point, intermolecular
Viscosity
he resistance of a liquid to flow
Stronger intermolecular forces →higher viscosity
You can look at the number of hydrogen bonds and what has bonds
Cohesive Forces
Cohesive forces: the forces that bind molecule to
each other in a liquid (IMFs)
✓because they have fewer neighbors, the surface
molecules are less stable (aka higher energy) than
those in the interior
✓leads liquids to minimize their surface are & minimize
interactions w/ surfaces
Surface Tension
Surface tension: the energy required to increase
the surface area by a given amount
✓ Water has a high surface tension due to its strong hydrogen bonds
Adhesive Forces
Adhesive forces: The IMFs between molecules of
a liquid and a solid surface are
✓If the adhesive forces are weak & the cohesive forces
are strong, the liquid will not “wet” the surface
✓When the adhesive forces are strong enough, the liquid
will “wet” the surface
Capillary Action
A liquid will climb up or down a narrow tube due to capillary action
Vaporization and Condensation
Some liquid molecules have enough kinetic energy to escape and be
a gas: vaporization or evaporation (liquid →gas)
- Some gas molecules have very little kinetic energy, therefore return
to liquid: condensation (gas →liquid) - Usually KE is lost to a surface (dust in clouds or condensation on a
glass).
Dynamic Equilibrium
Once the rates of vaporization and condensation are equal, total amount of vapor and liquid will not change:dynamic equilibrium
Vapor Pressure
- The pressure exerted by the vapor when it is in dynamic equilibrium with its liquid is the vapor pressure
- Liquids that evaporate easily are volatile
✓Weaker intermolecular forces → higher vapor pressure
✓Ethanol, gasoline, fingernail polish remover - Liquids that do not evaporate easily are nonvolatile
✓Stronger intermolecular forces → little or almost no vapor pressure
✓motor oil, antifreeze
All liquides exert a vapor at dynamic equilibrium
sublimation
phase change from a solid to a gas.
critical point
is the point at which two phases become indistinguishable from each other. It is found at the high-temperature extreme of the liquid–gas phase boundary.
supercritical fluid region
. A supercritical fluid is a region at which point distinct liquid and gas phases do not exist. It is found at the high-temperature extreme of the liquid–gas phase boundary.
the triple point
The triple point where the solid, liquid, and gas phases of CO₂ exist in equilibrium. It can be found at the intersection of the boundary lines for these phases.
