CH. 12: Intermolecular Forces- Liquids, Solids, and Phase Changes

Condensation, freezing, and deposition are (1)_____ phase changes, whereas melting, vaporization, and sublimation are (2)_____ changes.

1) exothermic 2) endothermic

As the temperature of a substance increases, the average (1)_____ energy of its particles also increases, and movement overcomes forces of (2)_____ more easily. As temperature decreases, particles move more slowly, and the (3)_____ forces between particles dominate.

1) kinetic 2) attractions 3) intermolecular

Describe bonding and intermolecular forces

1. Bonding forces are generally much stronger than intermolecular forces. 2. Intermolecular forces involve partial or small charges that are far apart and are relatively weak.

Describe dipole-dipole forces

1. For two compounds of similar molar mass, the greater the molecular dipole moment, the stronger the dipole-dipole forces. 2. Dipole-dipole forces are the forces of attraction between two polar molecules.

Water is unique in the way it behaves as a wonderful solvent of many substances. Describe why.

1. H2O dissolves polar non-ionic substances by hydrogen bonding and/or dipole-dipole forces. 2. H2O dissolves nonpolar gases through dipole-induced dipole and dispersion forces. 3. H2O dissolves ionic compounds through ion-dipole forces.

H2O exhibits extremely strong and efficient hydrogen bonding between its molecules. Describe why.

1. High capillarity 2. High surface tension 3. High specific heat capacity

Describe a phase equilibrium

1. If the rate of condensation is equal to the rate of evaporation, a phase equilibrium exists. 2. A system must be closed in order for a phase equilibrium to be established. 3. At equilibrium, the amount of the substance in each phase remains constant.

Describe nanotechnology and nanoscale materials.

1. Nanoscale materials can be constructed through processes using self-assembly and controlled orientation of molecules. 2. Nanoscale particles are found in nature. 3. Nanoscale materials exhibit distinct behaviors. 4. Nanotechnology involves the manipulation of materials whose sizes range from 1 to 100 nm.

Describe polymers

1. Polymers have large molecular masses. 2. Not all the molecules of a given polymer will have the same molecular mass. 3. Polymers are macromolecules made of repeating units called monomers.

List typical properties of ceramics

1. Strength 2. Thermal insulation 3. Hardness

List typical characteristics of molecules that form liquid crystal phases

1. Structure that promotes intermolecular attractions 2. Long, cylindrical shape

Describe the surface tension of a liquid

1. Surface tension is the amount of energy required to increase the surface area of a liquid by a unit area. 2. A polar liquid will have a higher surface tension than a nonpolar liquid. 3. Surface tension is the result of a net downward and inward force on the surface particles of a liquid.

Describe viscosity of a liquid

1. Viscosity is a liquid's resistance to flow. 2. The viscosity of a given liquid decreases with increasing temperature. 3. A liquid with stronger intermolecular forces will have a higher viscosity.

Water is often called the "universal solvent" because of its ability to dissolve so many substances. What are the means water behaves as a solvent?

1. Water dissolves ionic compounds through such strong ion-dipole forces that ions separate from their lattices and stay in solution. 2. Water dissolves polar substances through hydrogen bonding or dipole-dipole attractions. 3. Water dissolves nonpolar gases somewhat through dipole-induced dipole interactions.

A liquid rises against the pull of gravity through a narrow space through capillary action. This results from a competition between the (1)_____ intermolecular forces between the molecules of the liquid itself and the (2)____ forces between the liquid and the walls of the container.

1. cohesive 2. adhesive

Molecular orbital (MO) theory proposes that metals bond through the formation of extremely large numbers of MOs whose energies are so close that they form a "band" of MOs. The lower energy MOs form the valence band and are occupied by valence electrons. In metallic solids, the empty (1)_____ lies (2)_____ above the valence band at higher energy.

1. conduction band 2. directly

Bonding forces include ionic bonds, metallic bonds, and (1)_____bonds. These types of forces are much (2)_____than the forces of attraction between individual molecules, which are called (3)_____ forces.

1. covalent 2. stronger 3. intermolecular, nonbonding

A p-type semiconductor is formed by doping silicon with any Group 3A element. This (1)_____ the number of valence electrons available, creating (2) _____ sites into which Si electrons can migrate. This increases the conductivity of the material.

1. decreases 2. posistive

The attraction between an ion and a nearby polar molecule is called an ion - (1)_____interaction. This attractive force is important when a(n) (2)_____compound dissolves in a polar solvent such as H2O.

1. dipole 2. ionic

The surface tension of a liquid, the energy required to increase the surface area by a given amount, is dependent on (1)_____ and (2)_____.

1. intermolecular forces 2. temperature

In a molecular substance, the covalent bonds between the atoms hold the individual molecule together as a unit and are referred to as (1)_____ forces. The nonbonding forces of attraction between one individual molecule and another are called (2)_____ forces. The physical behavior of the phases of matter reflect the difference in the strength of their (3)_____.

1. intramolecular 2. intermolecular 3. intermolecular forces

The particles in a crystal are arranged in an orderly 3-D array called the crystal (1)_____ The simplest repeating unit of the crystal is called the unit (2)_____.

1. lattice 2. cell

When two polar molecules are close to each other they will orient themselves so that the positive pole of one molecule attracts the (1)_____ pole on the adjacent molecule. These intermolecular forces are called (2)_____ forces.

1. negative 2. dipole-dipole

Dispersion forces are the only type of intermolecular force exhibited by atoms and by (1)_____ molecules. Without the existence of dispersion forces, such substances could not exist in the (2)_____states of matter.

1. nonpolar 2. condensed

The (1)_____pattern (geometry) of H bonding in H2O gives ice a very open structure with large (2)_____ between the molecules. Water therefore differs from most liquids because it becomes (3)_____dense when it freezes.

1. tetrahedral 2. spaces 3. less

According to MO band theory, metals bond by forming a large number of (1)_____MOs whose energies are so close that they form a continuous band. The lower energy MOs, occupied by the valence electrons, form the (2)_____band, whereas the empty higher energy MOs form the (3)_____ band

1.delocalized/shared 2. valence 3. conduction

Nanomachine

A mechanical device whose components are on the nanoscale

Correctly describe a heating-cooling curve

A plot of heat vs. temperature for a substance that is heated or cooled at a constant rate and constant pressure

Network covalent solid

Atoms held together by covalent bonds

Nanocomposites

Bulk materials constructed from nanoscale particles to increase strength, ductility, and many other properties

Ionic solid

Cations and anions arranged in a regular lattice held together by ion-ion attraction

Liquid Crystal

Consist of a crystal phase that flows like a liquid but has an ordered shape

Nanostructured Material

Consist of materials that do not behave as atoms or as crystals; sizes range from 1 to 100 nm

Ceramic Material

Consists mostly of a network covalent solids formed at high temperature that are very resistant to heat and chemicals

Polymeric Material

Consists of extremely large molecules that adopt the shape of coils due to intermolecular forces

Molecular

Fairly soft with low melting points and poor conductors of heat and electricity

covalent radius

Half the distance between the nuclei of two covalently bonded atoms

van der Waals radius

Half the shortest distance between the nuclei of two identical nonbonded atoms

Ionic

Hard and brittle with high melting points, and good thermal and electrical conductivity in the molten phase

Nanotubes

High-surface-area self-assembling hollow nanostructures

Atomic solid

Individual atoms held together by dispersion forces

Molecular solid

Individual molecules held together by various combinations of intermolecular forces

_____involve the attraction between an charged particle and a nearby polar molecule. The most common example of such an intermolecular force of attraction is the dissolution of an ionic compound by water.

Ion-dipole forces

Quantum dots

Semiconducting materials that have discrete energy levels and are "tunable" to emit different wavelengths of light based on particle size

Metallic

Soft to hard, varying melting points, and excellent conductors of electricity and heat as well as malleable and ductile

bond length

The distance between the nuclei of two bonded atoms

How does the addition of phosphorus to silicon create an n-type semiconductor?

The extra electrons from the phosphorus atoms bridge the gap between the valence and conductance bands, increasing the conductivity.

Describe capillary action.

The rising of a liquid through a narrow space against gravity

van der Waals distance

The shortest distance between two non-bonded atoms in adjacent molecules

Polarizability

This is a measure of how the electron cloud around an atom responds to its electronic environment.

True or false: Many amorphous solids are formed from rapid cooling of molten crystals.

True

Network covalent

Very hard with high melting points but usually poor thermal and electrical conductors

Polymeric materials

are macromolecules containing covalently linked chains of smaller molecules called monomers.

Liquid crystals

are substances with an ability to flow but with a regular arrangement of particles in a lattice.

All _____ are nonmetallic inorganic compounds.

ceramics

The number of nearest neighbors for a particle (atoms or ions) in the unit cell of a crystal is called the _____ number of the particle.

coordination

A change in the physical state of a molecular substance does NOT involve the breaking of

covalent bonds.

Compounds that maintain an orderly arrangement of particles in the liquid phase are known as liquid _____

crystals

The resistance of large bodies of water to changes in temperature with the input of energy (typically radiant solar energy) is a result of water's

high specific heat capacity

The physical state of a molecular substance at a particular temperature and pressure depends on the strength of its

intermolecular forces.

Covalent Bonds are classified as

intramolecular forces

Intermolecular forces are the forces

of attraction between one individual molecule and another.

The term _____ is used to describe how well the electron cloud around an atom responds to changes in its electronic environment.

polarizability

The high capillary action of water is a result of its

strong hydrogen bonding

Water has a very high specific heat capacity compared to other common liquids. This property is due to _____ water.

strong hydrogen bonding in