ACE Chemistry
Q&A
Plasma - answer-Ionized gas that is considered fourth state of matter. Makes up most of visible
mass of universe, including all stars and interstellar medium. On Earth, exists in lightning, polar
aurorae, plasma torches, neon lights, and plasma TVs. Transmit Alfven waves and are
described by the Vlasov and Saha equation. Can be examined by a Langmuir probe and exhibit
Debye interaction length. Named by Langmuir.
Bose-Einstein Condensate - answer-Supercooled fifth state of matter created in 1995 by
Cornell, Wieman, and Ketterle using rubidium-87. Particles collapse into a single quantum
mechanical state, effectively forming a "super atom". A recent example is the Tonks-Girardeau
gas, and can be analyzed using the Gross-Pitaevskii equation.
Sublimation - answer-The direct transition from a solid to a gas. Used during lyophilization to
freeze-dry perishable materials. Occurs at temperatures and pressures less than the triple point.
The enthalpy of sublimation is the sum of the enthalpies of fusion and vaporization. Occurs in
dry ice, solid iodine, naphthalene (the main component of moth balls). When done in lab, often
followed by "cold finger" for condensing.
Deposition - answer-Direct transition from a gas to a solid. Snow in clouds and frost on windows
form by deposition. Chemical-vapor type used to form synthetic diamonds. Easiest method for
vitrifying water.
Triple point - answer-Temperature and pressure at which a substance exists as a solid, liquid,
and gas in equilibrium. For water, defines the Kelvin scale. Gibbs phase rule says a pure
substance has no degrees of freedom at the triple point. Any system has p choose three triple
points, where p is the number of phases. Helium-4 has two triple points called lambda points
because of superfluidity.
Critical point - answer-Temperature and pressure where a phase boundary ceases to exist.
Clausius-Clapeyron Equation - answer-Gives the slope of a coexistence curve for a phase
change in a pressure vs. temperature plot. One version of it is called the Antoine equation.
Explains the nonlinear relation between the temperature of a liquid and its vapor pressure. Can
be used to model cloud formation.
Gold Foil Experiment (or Geiger-Marsden Experiment) - answer-Alpha particles (helium nuclei)
fired at a very thin sheet of gold foil. Surrounding sheet of zinc sulfide would light up when
struck by an alpha particle. Wide deflection of some particles could only be explained by a
dense mass within atoms: the nucleus. The Rutherford (planetary) model of the atom
supplanted the Plum Pudding model based on the experiment. Originally sought to prove Plum
Pudding Model of atom.
, Deuterium - answer-H-2. Found in heavy water. Often found in solvents for NMR spectroscopy.
Almost all was made during Big Bang. Produced in first step of proton-proton chain. Used to
slow down enzymes in the primary isotope effect.
Tritium - answer-H-3. Commonly produced by bombarding lithium with neutrons. A small
amount is formed when cosmic rays strike atmospheric nitrogen. Used in self-powered beta
lights found in watches and exit signs. Necessary for a hydrogen bomb.
Carbon-14 - answer-Used in radiocarbon dating of organic samples. Becomes incorporated into
organic compounds by photosynthesis. Discovered by Kamen and Ruben. Half-life of 5730
years. Decays into nitrogen-14 through beta decay.
Uranium-235 - answer-Main fuel of fission reactors where it splits into barium-141 and krypton-
92. Used in "Little Boy" bomb on Hiroshima.
Isotope - answer-Atoms with the same atomic number (number of protons) but different mass
numbers (different number of neutrons).
Allotrope - answer-Different structural forms of an element in the same state of matter at room
temperature.
Allotropes of phosphorus - answer-White phosphorus has a tetrahedral arrangement of atoms.
Used in weapons because it will ignite spontaneously at low temperatures. Red phosphorus is
an amorphous solid used in match tips. Also purple and black allotropes.
Allotropes of oxygen - answer-Monatomic oxygen is a highly reactive free radical that is rare on
Earth but common in the upper atmosphere. DIatomic oxygen is the most common allotrope on
Earth. Ozone is a destructive pollutant on Earth but forms a layer of the stratosphere that
shields the Earth from UV radiation.
Allotropes of carbon - answer-Diamond is the hardest known natural mineral. Graphite is the
most stable allotrope, found in pencils, lubricants, and arc lamps. A single layer of graphite is
called graphene. Fullerenes like buckyballs and nanotubes are at the heart of nanotechnology.
Valence Shell Electron Pair Repulsion (VSEPR) theory - answer-Pairs of valence electrons
surrounding an atom arrange themselves to be as far apart as possible. Developed by Gillespie
and Nyholm. Based on the steric number, or the number of electron pairs around an atom. Must
account for both shared pairs (bonds) and lone pairs. Common shapes are linear, bent, trigonal
planar, trigonal pyramidal, tetrahedral, trigonal bipyramidal, octahedral, seesaw, T-shaped, and
square planar.
Molecular Orbital (MO) theory - answer-Alternative to VSEPR theory based on regions of
electron density called orbitals. Most common molecular orbitals are called sigma and pi. There
are bonding and nonbonding (marked with an asterisk) types. Molecular orbitals are determined
Q&A
Plasma - answer-Ionized gas that is considered fourth state of matter. Makes up most of visible
mass of universe, including all stars and interstellar medium. On Earth, exists in lightning, polar
aurorae, plasma torches, neon lights, and plasma TVs. Transmit Alfven waves and are
described by the Vlasov and Saha equation. Can be examined by a Langmuir probe and exhibit
Debye interaction length. Named by Langmuir.
Bose-Einstein Condensate - answer-Supercooled fifth state of matter created in 1995 by
Cornell, Wieman, and Ketterle using rubidium-87. Particles collapse into a single quantum
mechanical state, effectively forming a "super atom". A recent example is the Tonks-Girardeau
gas, and can be analyzed using the Gross-Pitaevskii equation.
Sublimation - answer-The direct transition from a solid to a gas. Used during lyophilization to
freeze-dry perishable materials. Occurs at temperatures and pressures less than the triple point.
The enthalpy of sublimation is the sum of the enthalpies of fusion and vaporization. Occurs in
dry ice, solid iodine, naphthalene (the main component of moth balls). When done in lab, often
followed by "cold finger" for condensing.
Deposition - answer-Direct transition from a gas to a solid. Snow in clouds and frost on windows
form by deposition. Chemical-vapor type used to form synthetic diamonds. Easiest method for
vitrifying water.
Triple point - answer-Temperature and pressure at which a substance exists as a solid, liquid,
and gas in equilibrium. For water, defines the Kelvin scale. Gibbs phase rule says a pure
substance has no degrees of freedom at the triple point. Any system has p choose three triple
points, where p is the number of phases. Helium-4 has two triple points called lambda points
because of superfluidity.
Critical point - answer-Temperature and pressure where a phase boundary ceases to exist.
Clausius-Clapeyron Equation - answer-Gives the slope of a coexistence curve for a phase
change in a pressure vs. temperature plot. One version of it is called the Antoine equation.
Explains the nonlinear relation between the temperature of a liquid and its vapor pressure. Can
be used to model cloud formation.
Gold Foil Experiment (or Geiger-Marsden Experiment) - answer-Alpha particles (helium nuclei)
fired at a very thin sheet of gold foil. Surrounding sheet of zinc sulfide would light up when
struck by an alpha particle. Wide deflection of some particles could only be explained by a
dense mass within atoms: the nucleus. The Rutherford (planetary) model of the atom
supplanted the Plum Pudding model based on the experiment. Originally sought to prove Plum
Pudding Model of atom.
, Deuterium - answer-H-2. Found in heavy water. Often found in solvents for NMR spectroscopy.
Almost all was made during Big Bang. Produced in first step of proton-proton chain. Used to
slow down enzymes in the primary isotope effect.
Tritium - answer-H-3. Commonly produced by bombarding lithium with neutrons. A small
amount is formed when cosmic rays strike atmospheric nitrogen. Used in self-powered beta
lights found in watches and exit signs. Necessary for a hydrogen bomb.
Carbon-14 - answer-Used in radiocarbon dating of organic samples. Becomes incorporated into
organic compounds by photosynthesis. Discovered by Kamen and Ruben. Half-life of 5730
years. Decays into nitrogen-14 through beta decay.
Uranium-235 - answer-Main fuel of fission reactors where it splits into barium-141 and krypton-
92. Used in "Little Boy" bomb on Hiroshima.
Isotope - answer-Atoms with the same atomic number (number of protons) but different mass
numbers (different number of neutrons).
Allotrope - answer-Different structural forms of an element in the same state of matter at room
temperature.
Allotropes of phosphorus - answer-White phosphorus has a tetrahedral arrangement of atoms.
Used in weapons because it will ignite spontaneously at low temperatures. Red phosphorus is
an amorphous solid used in match tips. Also purple and black allotropes.
Allotropes of oxygen - answer-Monatomic oxygen is a highly reactive free radical that is rare on
Earth but common in the upper atmosphere. DIatomic oxygen is the most common allotrope on
Earth. Ozone is a destructive pollutant on Earth but forms a layer of the stratosphere that
shields the Earth from UV radiation.
Allotropes of carbon - answer-Diamond is the hardest known natural mineral. Graphite is the
most stable allotrope, found in pencils, lubricants, and arc lamps. A single layer of graphite is
called graphene. Fullerenes like buckyballs and nanotubes are at the heart of nanotechnology.
Valence Shell Electron Pair Repulsion (VSEPR) theory - answer-Pairs of valence electrons
surrounding an atom arrange themselves to be as far apart as possible. Developed by Gillespie
and Nyholm. Based on the steric number, or the number of electron pairs around an atom. Must
account for both shared pairs (bonds) and lone pairs. Common shapes are linear, bent, trigonal
planar, trigonal pyramidal, tetrahedral, trigonal bipyramidal, octahedral, seesaw, T-shaped, and
square planar.
Molecular Orbital (MO) theory - answer-Alternative to VSEPR theory based on regions of
electron density called orbitals. Most common molecular orbitals are called sigma and pi. There
are bonding and nonbonding (marked with an asterisk) types. Molecular orbitals are determined
