Gen Chem Key Terms Ch.4 (Redox) - Ch.7 (De Broglie Wavelength)

oxidation number (O.N.)

(also oxidation state) A number equal to the magnitude of the charge an atom would have if its shared electrons were transferred to the atom that attracts them more strongly.

oxidation-reduction reaction

(also redox reaction) A process in which there is a net movement of electrons from one reactant (reducing agent) to another (oxidizing agent).

oxidizing agent

The substance that accepts electrons in a reaction and undergoes a decrease in oxidation number.

reducing agent

The substance that donates electrons in a redox reaction and undergoes an increase in oxidation number.

reduction

The gain of electrons by a species, accompanied by a decrease in oxidation number.

atmosphere

The mixture of gases that extends from a planet’s surface and eventually merges with outer space. (For the unit, see standard atmosphere.)

Avogadro's law

The gas law stating that, at fixed temperature and pressure, equal volumes of any ideal gas contain equal numbers of particles, and, therefore, the volume of a gas is directly proportional to its amount (mol): V ∝ n.

barometer

A device used to measure atmospheric pressure. Most commonly, a tube open at one end, which is filled with mercury and inverted into a dish of mercury.

Boyle's law

The gas law stating that, at constant temperature and amount of gas, the volume occupied by a gas is inversely proportional to the applied (external) pressure: V ∝ 1/P.

Charles's law

The gas law stating that, at constant pressure, the volume occupied by a fixed amount of gas is directly proportional to its absolute temperature: V ∝ T.

collision frequency

The average number of collisions per second that a particle undergoes.

Dalton's law of partial pressures

A gas law stating that, in a mixture of unreacting gases, the total pressure is the sum of the partial pressures of the individual gases: Ptotal = P1 + P2 + P3 + ….

diffusion

The movement of one fluid through another.

effusion

The process by which a gas escapes from its container through a tiny hole into an evacuated space.

Graham's law of effusion

A gas law stating that the rate of effusion of a gas is inversely proportional to the square root of its density (or molar mass)

ideal gas

A hypothetical gas that exhibits linear relationships among volume, pressure, temperature, and amount (mol) at all conditions; approximated by simple gases at ordinary conditions.

ideal gas law

(also ideal gas equation) An equation that expresses the relationships among volume, pressure, temperature, and amount (mol) of an ideal gas: PV = nRT.

kinetic-molecular theory

The model that explains macroscopic gas behavior in terms of particles in random motion whose volumes and interactions are negligible.

manometer

A device used to measure the pressure of a gas in a laboratory experiment.

mean free path

The average distance a particle travels between collisions at a given temperature and pressure.

millimeter of mercury (mmHg)

A unit of pressure based on the difference in the heights of mercury in a barometer or manometer. Renamed the torr in honor of Torricelli.

mole fraction (X)

A concentration term expressed as the ratio of number of moles of solute to the total number of moles (solute plus solvent).

partial pressure

The portion of the total pressure contributed by a gas in a mixture of gases.

pascal (Pa)

The SI unit of pressure; 1 Pa = 1 N/m2.

pressure (P)

The force exerted per unit of surface area.

rms (root-mean-square) speed (urms)

The speed of a molecule having the average kinetic energy; very close to the most probable speed.

standard atmosphere (atm)

The average atmospheric pressure measured at sea level and 0°C, defined as 1.01325 × 105 Pa.

standard molar volume

The volume of 1 mol of an ideal gas at standard temperature and pressure: 22.4141 L.

standard temperature and pressure (STP)

The reference conditions for a gas: 0°C (273.15 K) and 1 atm (760 torr).

torr

A unit of pressure identical to 1 mmHg.

universal gas constant (R)

A proportionality constant that relates the energy, amount of substance, and temperature of a system; R = 0.0820578 atm·L/mol·K = 8.31447 J/mol·K.

van der Waals constants

Experimentally determined positive numbers used in the van der Waals equation to account for the interparticle attractions and particle volume of real gases.

van der Waals equation

An equation that accounts for the behavior of real gases.

biomass fuel

A fuel composed of biological materials such as plant and animal matter.

calorie (cal)

A unit of energy defined as exactly 4.184 joules; originally defined as the heat needed to raise the temperature of 1 g of water 1°C (from 14.5°C to 15.5°C).

calorimeter

A device used to measure the heat released or absorbed by a physical or chemical process taking place within it.

change in enthalpy (ΔH)

The change in the system’s internal energy plus the product of the constant pressure and the change in volume: ΔH = ΔE + PΔV; alternatively, the heat lost or gained at constant pressure: ΔH = qP.

endothermic process

A process that occurs with an absorption of heat from the surroundings and therefore an increase in the enthalpy of the system (ΔH > 0).

enthalpy (H)

A thermodynamic quantity that is equal to the system's internal energy plus the product of the pressure and volume.

enthalpy diagram

A graphic depiction of the enthalpy change of a system.

exothermic process

A process that occurs with a release of heat to the surroundings and therefore a decrease in the enthalpy of the system (ΔH < 0).

formation equation

An equation in which 1 mole of a compound forms from its elements.

fossil fuel

Any fuel, including coal, petroleum, and natural gas, derived from the products of the decay of dead organisms.

heat (q)

(also thermal energy) The energy transferred between objects because of a difference in their temperatures only.

heat capacity (C)

The quantity of heat required to change the temperature of an object by 1 K.

Hess's law

A law stating that the enthalpy change of an overall process is the sum of the enthalpy changes of the individual steps.

internal energy (E)

The sum of the kinetic and potential energies of all the particles in a system.

joule (J)

The SI unit of energy; 1 J = 1 kg · m2/s2.

law of conservation of energy

(also first law of thermodynamics) A basic observation that the total energy of the universe is constant; thus, ΔEuniverse = ΔEsystem + ΔEsurroundings = 0.

molar heat capacity (Cm)

The quantity of heat required to change the temperature of 1 mol of a substance by 1 K.

photovoltaic cell

A device capable of converting light directly into electricity.

pressure-volume work

(also PV work) A type of mechanical work done when a volume change occurs against an external pressure.

specific heat capacity (c)

The quantity of heat required to change the temperature of 1 gram of a substance or material by 1 K.

standard enthalpy of formation ΔH°f

(also standard heat of formation) The enthalpy change occurring when 1 mol of a compound forms from its elements with all components in their standard states.

standard enthalpy of reaction ΔH°rxn

(also standard heat of reaction) The enthalpy change that occurs during a reaction when all components are in their standard states.

standard state

A set of specific conditions used to compare thermodynamic data: 1 atm for gases behaving ideally, 1 M for dissolved species, or the pure substance for liquids and solids.

state function

A property of a system determined only by the system's current state, regardless of how it arrived at that state.

surroundings

All parts of the universe other than the system being considered.

system

The defined part of the universe under study.

thermochemical equation

A balanced chemical equation that includes the enthalpy change for the reaction.

thermochemistry

The branch of thermodynamics that focuses on the heat involved in chemical and physical change.

thermodynamics

The study of energy and its transformations.

work (w)

The energy transferred when an object is moved by a force.

absorption spectrum

The spectrum produced when atoms absorb specific wavelengths of incoming light and become excited from lower to higher energy levels.

amplitude

The height of the crest (or depth of the trough) of a wave; related to the intensity of the energy (brightness of the light).

de Broglie wavelength

The wavelength of a moving particle obtained from the de Broglie equation: λ = h/mu.

diffraction

The phenomenon in which a wave striking the edge of an object bends around it. A wave passing through a slit as wide as its wavelength forms a circular wave.

electromagnetic radiation (also electromagnetic energy or radiant energy)

Oscillating, perpendicular electric and magnetic fields moving simultaneously through space as waves and manifested as visible light, x-rays, microwaves, radio waves, and so on.

electromagnetic spectrum

The continuum of radiant energy arranged in order of increasing wavelength.

emission spectrum

The line spectrum produced when excited atoms return to lower energy levels and emit photons characteristic of the element.

oxidation

The loss of electrons by a species, accompanied by an increase in oxidation number.

excited state

Any electron configuration of an atom (or ion or molecule) other than the lowest energy (ground) state.

flame test

A procedure for identifying the presence of metal ions in which a granule of a compound or a drop of its solution is placed in a flame to observe a characteristic color.

frequency (ν)

The number of complete waves, or cycles, that pass a given point per second, expressed in units of 1/second, or s−1 [also called hertz (Hz)]; related inversely to wavelength.

ground state

The electron configuration of an atom (or ion or molecule) that is lowest in energy.

infrared (IR)

The region of the electromagnetic spectrum between the microwave and visible regions.

level (also shell)

A specific energy state of an atom given by the principal quantum number n.

line spectrum

A series of separated lines of different colors representing photons whose wavelengths are characteristic of an element. (See also emission spectrum.)

photoelectric effect

The observation that, when monochromatic light of sufficient frequency shines on a metal, an electric current is produced.

photon

A quantum of electromagnetic radiation.

Planck's constant (h)

A proportionality constant relating the energy and frequency of a photon, equal to 6.626 × 10−34 J·s.

principal quantum number (n)

A positive integer that specifies the energy and relative size of an atomic orbital; a number that specifies an energy level in an atom.

quantum

A packet of energy equal to hν. The smallest quantity of energy that can be emitted or absorbed.

quantum mechanics

The branch of physics that examines the wave nature of objects on the atomic scale.

quantum number

A number that specifies a property of an orbital or an electron.

refraction

A phenomenon in which a wave changes its speed and therefore its direction as it passes through a phase boundary into a different medium.

spectrometry

Any instrumental technique that uses a portion of the electromagnetic spectrum to measure the atomic and molecular energy levels of a substance.

speed of light (c)

A fundamental constant giving the speed at which electromagnetic radiation travels in a vacuum: c = 2.99792458 × 108 m/s.

stationary state

In the Bohr model, one of the allowable energy levels of the atom in which it does not release or absorb energy.

sublevel (also subshell)

An energy substate of an atom within a level. Given by the n and l values, the sublevel designates the size and shape of the atomic orbitals.

wavelength (λ)

The distance between any point on a wave and the corresponding point on the next wave, that is, the distance a wave travels during one cycle.

wave-particle duality

The principle stating that both matter and energy have wavelike and particle-like properties.