Chapter 10

Question 1

IMF

Answer 1

Inter molecular forces
-Forces of attraction

• Gas-weak
• Liquide-Moderate
• Solid-Strong

Question 2

Intramolecular Force

Answer 2

Those that hold the atoms together within the molecule (covalent bonds)

Question 3

Intermolecular forces

Answer 3

attractions between molecules

Question 4

Three types of intermolecular forces in Pure substances

Answer 4

• London dispersion force

Question 5

Dispersion Force

Answer 5

-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

Question 6

Strength of intermolecular forces

Answer 6

Can be measured by boiling point

Question 7

Polarizability:

Answer 7

The ease with which the electron cloud can be distorted by neighboring charges

Question 8

Dipole-Dipole Forces

Answer 8

• 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

Question 9

Hydrogen Bonding

Answer 9

-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

Question 10

Dispersion Forces

Answer 10

the weakest, present in all molecules
✓Increase with increasing molar mass
✓Can be significant in large molecules

Higher boiling point for stronger forces

Question 11

Ion-dipole forces

Answer 11

An attractive force that results from the electrostatic attraction between an ion and a neutral molecule that has a dipole.

Answer 12

There will be questions on ranking boiling point, intermolecular

Question 13

Viscosity

Answer 13

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

Question 14

Cohesive Forces

Answer 14

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

Question 15

Surface Tension

Answer 15

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

Question 16

Adhesive Forces

Answer 16

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

Question 17

Capillary Action

Answer 17

A liquid will climb up or down a narrow tube due to capillary action

Question 18

Vaporization and Condensation

Answer 18

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).

Question 19

Dynamic Equilibrium

Answer 19

Once the rates of vaporization and condensation are equal, total amount of vapor and liquid will not change:dynamic equilibrium

Question 20

Vapor Pressure

Answer 20

• 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

Question 21

sublimation

Answer 21

phase change from a solid to a gas.

Question 22

critical point

Answer 22

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.

Question 23

supercritical fluid region

Answer 23

. 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.

Question 24

the triple point

Answer 24

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.

Question 25

phase diagram

Answer 25

combines plots of pressure versus temperature for the liquid-gas, solid-liquid, and solid-gas phase-transition equilibria of a substance. These diagrams indicate the physical states that exist under specific conditions of pressure and temperature, and also provide the pressure dependence of the phase-transition temperatures (melting points, sublimation points, boiling points).

Question 26

crystalline solids

Answer 26

solids in which the atoms, ions, or molecules are arranged in a definite repeating pattern.

Usually Metals and ionic compounds

Question 27

amorphous solids

Answer 27

The particles of such solids lack an ordered internal structure and are randomly arranged

Substances that consist of large molecules, or a mixture of molecules whose movements are more restricted, often form amorphous solids.

Question 28

Ionic Solids

Answer 28

Ionic solids: consist of positive & negative ions held together by electrostatic forces (ionic bonds
✓Typically have high melting pts
✓Are hard but brittle
✓Don’t conduct electricity in solid state
➢but do in liq. state or solution

Question 29

Metallic solids

Answer 29

Metallic solids: atoms held together by metallic bonds
✓“Sea of electrons” model
✓High thermal & electrical conductivity
✓Metallic luster
✓Are ductile & malleable
✓Many are hard & strong

Question 30

Covalent Network Solid

Answer 30

Covalent network solids: atoms held together by covalent bonds, throughout
✓Very hard & strong
✓Have high melting pts
✓Don’t conduct electricity well

To ID you would need to know something about repeating patterns

Properties: very hard, not conductive, very high melting points

Question 31

Molecular solids,

Answer 31

Molecular solids: composed of neutral molecules, held together by IMFs
✓Melting pts vary, but typically not very high
✓Many are soft & waxy
✓Don’t conduct electricity

are composed of neutral molecules. The strengths of the attractive forces between the units present in different crystals vary widely

Properties: variable hardness, variable brittleness, not conductive, low melting points

Question 32

Boiling Point

Answer 32

Vapor pressure increases with temperature

When vapor pressure = external pressure (horizontal line), the liquid boils (that temp = boiling point)

The boiling point is dependent on the external pressure
✓ Higher external pressure → higher boiling point
✓ Lower external pressure →lower boiling point

Question 33

Deposition

Answer 33

Gas to solid phase change

Question 34

Supercritical Fluids

Answer 34

Above the critical point, the meniscus between the liquid and
vapor disappears and the states commingle to form a
supercritical fluid
✓ The temp. & press. of this are the critical temperature and critical
pressure
* Supercritical fluid have properties of both gas and liquid states:
✓ Fills confines of container (like a gas)
✓ Does not behave like an ideal gas
✓ Density more like that of a liquid
✓ But density increases continuously as the pressure is increased

Question 35

Allotropes

Answer 35

Some elements can exist in multiple solid forms,
called allotropes

Question 36

Crystal Defects

Answer 36

Crystalline solids can have defects
* Vacancy: place in the crystal struct. that is missing an atom/ion
* Interstitial site: an atom/ion occupies a site in between the usual sites of the crystal struct.
* Substitution site: one atom/ion in the crystal struct. is replaced by a diff. one (impurity)
✓ can be done intentionally (or naturally), altering the properties of the material: doping

Question 36

Crystal Defects

Answer 36

Crystalline solids can have defects
* Vacancy: place in the crystal struct. that is missing an atom/ion
* Interstitial site: an atom/ion occupies a site in between the usual sites of the crystal struct.
* Substitution site: one atom/ion in the crystal struct. is replaced by a diff. one (impurity)
✓ can be done intentionally (or naturally), altering the properties of the material: doping