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Salt an ionic compound
Salt bridge a tube containing an electrolyte that connects the two compartments of a galvanic cell, allowing ion flow without extensive mixing of the different solutions
Saturated Solution A solution containing the maximum amount of solute that a given quantity of solvent can dissolve at a given temperature; a solution in which equilibrium exists between the dissolved and undissolved solute
Scientific method the process of studying natural phenomena, involving observations, forming laws and theories, and testing of theories by experimentation
Scintillation counter an instrument that measures radioactive decay by sensing the flashes of light produced in a substance by the radiation
Screening Effect Reduction of the attraction between the nuclear charge and the highest-energy-level electrons, caused by the presence of electrons in lower energy levels
Second law of thermodynamics in any spontaneous process, there is always an increase in the entropy of the universe
Second-Order Rate Equation A rate equation in which the rate is proportional to the second power of the concentration of one reactant or to the first power of the concentration of each of two reactants
Secondary structure (of a protein) the three-dimensional structure of the protein chain (for example, a-helix, random coil, or pleated sheet)
Sedimentary Rocks Rocks formed on the earth's surface or sea floor from small particles or dissolved substances from other rocks
Selective precipitation a method of separating metal ions from an aqueous mixture by using a reagent whose anion forms a precipitate with only one or a few of the ions in the mixture
Semiconductor a substance conducting only a slight electrical current at room temperature, but showing increased conductivity at higher temperatures
Semipermeable Membrane A membrane that allows the passage of only some components of a solution
Shielding the effect by which the other electrons screen, or shield, a given electron from some of the nuclear charge
Sl units International System of units based on the metric system and units derived from the metric system
Side chain (of amino acid) the hydrocarbon group on an amino acid represented by H, CH3, or a more complex substituent
Sigma Bond A covalent bond in which the electron density is symmetrical about the internuclear axis
Significant figures the certain digits and the first uncertain digit of a measurement
Silica the fundamental silicon-oxygen compound, which has the empirical formula SiO2, and forms the basis of quartz and certain types of sand
Silicates salts that contain metal cations and polyatomic siticon-oxygen anions that are usually polymeric
Single Bond a bond in which one pair of electrons is shared by two atoms
Singlet An electron energy state in which electron spins are all paired
Smelting a metallurgical process that involves reducing metal ions to the free metal
Solid Solution A homogeneous solid mixture
Solubility the amount of a substance that dissolves in a given volume of solvent at a given temperature
Solubility product constant the constant for the equilibrium expression representing the dissolving of an ionic solid in water
Solute a substance dissolved in a liquid to form a solution
Solution a homogeneous mixture
Solvent the dissolving medium in a solution
Somatic damage radioactive damage to an organism resulting in its sickness or death (
Space-filling model a model of a molecule showing the relative sizes of the atoms and their relative orientations
Specific heat capacity The amount of energy required to elevate the temperature of one gram of a substance one degree Celsius
Spectator Ions Ions present in a solution that do not participate in a chemical reaction
Spectrochemical series a listing of ligands in order based on their ability to produce d-orbital splitting
Spectrophotometer An instrument for measuring the intensity of radiation absorbed at different wavelengths
Spectroscope A device for dispersing radiation into a spectrum so that the component wavelengths can be observed
Spectrum An array of the components of radiation separated in order of some varying property such as wavelength
Spin Quantum Number The quantum number that specifies the spin state of an electron
Spontaneous fission the spontaneous splitting of a heavy nuclide into two lighter nuclides
Spontaneous process a process that occurs without outside intervention
Standard atmosphere a unit of pressure equal to 760 mm Hg
Standard Electrode Potential The potential of a half-cell when all reactants are present in their standard states relative to the standard hydrogen electrode Normally, standard electrode potentials are for reduction reactions
Standard Electromotive Force The potential of' a cell when all reactants are present in their standard states
Standard enthalpy of formation the enthalpy change that accompanies the formation of one mote of a compound at 25oC from its elements, with all substances in their standard states at that temperature
Standard free energy change the change in free energy that will occur for one unit of reaction if the reactants in their standard states are converted to products in their standard states
Standard free energy of formation the change in free energy that accompanies the formation of one mole of a substance from its constituent elements with all reactants and products in their standard states
Standard reduction potential the potential of a half-reaction under standard state conditions, as measured against the potential of the standard hydrogen electrode
Standard State A reference state for thermodynamic measurements, defined for a liquid or solid as the pure substance at one atmosphere external pressure, for a gas as an ideal gas at one atmosphere pressure, and for a solution as a 1 M solution, in each case at the specified temperature
Standard solution a solution whose concentration is accurately known
Standard temperature and pressure (STP) the condition of 273 K and 1 atm pressure
Standing wave a stationary wave as on a string of a musical instrument; in the wave mechanical model, the electron in the hydrogen atom is considered to be a standing wave
State function A function whose value depends only on the state of a substance and not on the path by which the state was reached
States of matter the three different forms in which matter can exist: solid, liquid, and gas
Steam cracking a process whereby hydrocarbon molecules are broken into small fragments by steam at very high temperatures
Stereoisomers Isomers differing only in the spatial arrangement of the atoms
Steric factor the factor (always less than one) that reflects the fraction of collisions with orientations that can produce a chemical reaction
Steroid the factor (always less than one) that reflects the fraction of collisions with orientations that can produce a chemical reaction
Stoichiometry The quantitative relationships among the reactants and products in a chemical reaction as expressed by the equation for the reaction
Stoichiometric quantities quantities of reactants mixed in exactly the correct amounts so that all are used up at the same time
Storage Cell A voltaic cell that is rechargeable by electric energy from an external source through reversal of the cell reaction
Strong acid an acid that completely dissociates to produce an H+ ion and the conjugate base
Strong base a metal hydroxide salt that completely dissociates into its ions in water
Strong electrolyte a material which, when dissolved in water, gives a solution that conducts an electric current very efficiently
Structural formula the representation of a molecule in which the relative positions of the atoms are shown and the bonds are indicated by lines
Structural isomerism isomerism in which the isomers contain the same atoms but one or more bonds differ
Subcritical reaction (nuclear) a reaction in which less than one neutron causes another fission event and the process dies out
Sublimation The transformation of a solid directly to a vapor without forming a liquid
Subshell a set of orbitals with a given azimuthal quantum number
Subsidiary Quantum Number The quantum number that specifies the number of nodal planes passing through the nucleus in the wave function
Substitution Reaction A reaction in which one atom or group of atoms is replaced by another
Supercooling the process of cooling a liquid below its freezing point without its changing to a solid
Supercritical reaction (nuclear) a reaction in which more than one neutron from each fission event causes another fission event The process rapidly escalates to a violent explosion
Superheating the process of heating a liquid above its boiling point without its boiling
Superoxide a compound containing the O2 anion
Supersaturated Solution An unstable solution containing more solute than a given amount of solvent can dissolve at a given temperature; a solution in a nonequilibrium condition in which saturation is exceeded
Surface-Active Agent Surfactant A substance that acts to reduce surface tension, especially between hydrophilic and hydrophobic phases
Surface tension the resistance of a liquid to an increase in its surface area
Surfactant a wetting agent, such as soap, that assists water in wetting and suspending nonpolar materials
Surroundings The portion of matter or space outside that which is under consideration as a system
Syndiotactic chain a polymer chain in which the substituent groups such as CH3 are arranged on alternate sides of the chain
System (thermodynamic) that part of the universe on which attention is to be focused
Systematic error an error that always occurs in the same direction

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