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Chemistry Dictionary Terminology "A"
Chemistry Dictionary Terminology  "S"

Salt Bridge
A U-shaped tube containing electrolyte, which connects two half-cells of a voltaic cell.
Saponification
Hydrolysis of esters in the presence of strong soluable bases.
Saturated Hydrocarbons
Hydrocarbons that contain only single bonds. They are also called alkanes or paraffin hydrocarbons.
Saturated Solution
Solution in which no more solute will dissolve.
Second Law of Thermodynamics
The universe tends toward a state of greater diorder in spontaneous processes.
Secondary Standard
a solution that has been titrated against a primary standard. A standard solution is a secondary standard.
Secondary Voltaic Cells
Voltaic cells that can be recharged; original reactanats can be regenerated be reversing the direction of the current flow.
Semiconductor
A substance that does not conduct electricity at low temperatures but does so at higher temperatures.
Semipermable Membrane
A thin partition between two solutions through which certain molecules can pass but others cannot.
Shielding Effect
Electrons in filled sets of s , p orbitals between the nucleus and outer shell electrons shield the outer shell electrons somewhat from the effect of protons in the nucleus; also called screening effect.
Sigma Bonds
Bonds resulting from the head-on overlap of atomic orbitals, in which the region of electron sharing is along and (cylindrically) symmetrical to the imaginary line connecting the bonded atoms.
Sigma Orbital
Molecular orbital resulting from head-on overlap of two atomic orbitals.
Silicones
Polymeric organosilicon compounds; contain individual or cross-linked Si-O chains or rings in which some oxygens of SiO4 tetrahedra are replaced by other groups.
Single Bond
Covalent bond resulting from the sharing of two electrons (one pair) between two atoms.
Solubility Product Constant
Equilibrium constant that applies to the dissolution of a slightly soluble compound.
Solubility Product Principle
The solubility product constant expression for a slightly soluble compound is the product of the concentrations of the constituent ions, each raised to the power that corresponds to the number of ions in one formula unit.
Solute
The dispersed (dissolved) phase of a solution.
Solution
Homogeneous mixture of two or more substances.
Solvation
The process by which solvent molecules surround and interact with solute ions or molecules.
Solvent
The dispersing medium of a solution.
Solvolysis
The reaction of a substance with the solvent in which it is dissolved.
S Orbital
A spherically symmetrical atomic orbital; one per energy level.
Specific Gravity
The ratio of the density of a substance to the density of water.
Specific Heat
The amount of heat required to raise the temperature of one gram of substance one degree Celsius.
Specific Rate Constant
An experimentally determined (proportionality) constant, which is different for different reactions and which changes only with temperature; k in the rate-law expression: Rate = k [A] x [B]v.
Spectator Ions
Ions in a solution that do not participate in a chemical reaction.
Spectral Line
Any of a number of lines corresponding to definite wavelengths of an atomic emission or absorption spectrum; represents the energy difference between two energy levels.
Spectrochemical Series
Arrangement of ligands in order of increasing ligand field strength.
Spectrum
Display of component wavelengths (colours) of electromagnetic radiation.
Square Planar
A term used to describe molecules and polyatomic ions that have one atom in the center and four atoms at the corners of a square.
Square Planar Complex
Complex in which the metal is in the center of a square plane, with ligand donor atoms at each of the four corners
Standard Electrodes
Half-cells in which the oxidized and reduced forms of a species are present at unit activity; 1.0M solutions of dissolved ions, 1.0atm partial pressure of gases, and pure solids and liquids.
Standard Electrode Potential
By convention , potential, Eo, of a half-reaction as a reduction relative to the standard hydrogen electrode when all species are present at unit activity.
Standard Entropy
The absolute entropy of a substance in its standard state at 298 K.
Standard Molar Enthalphy of Formation
The amount of heat absorbed in the formation of one mole of a substance in a specified state from its elements in their standard states.
Standard Molar Volume
The volume occupied by one mole of an ideal gas under standard conditions; 22.4liters.
Standard Reaction
A reaction in which the numbers of moles of reactants shown in the balanced equation, all in their standard states, are completely converted to the numbers of moles of products shown in the balanced equation, also sall at their standard state.
Stereoisomers
Isomers that differ only in the way that atoms are oriented in space; consist of geometrical and optical isomers.
Stoichiometry
Description of the quantitative relationships among elements and compounds as they undergo chemical changes.
Strong Electrolyte
A substance that conducts electricity well in a dilute aqueous solution.
Strong Field Ligand
Ligand that exerts a strong crystal or ligand electrical field and generally forms low spin complexes with metal ions when possible.
Structural Isomers
Compounds that contain the same number of the same kinds of atoms in different geometric arrangements.
Sublimation
The direct vaporization of a sold by heating without passing through the liquid state.
Substance
Any kind of matter all specimens of which have the same chemical composition and physical properties.
Substitution Reaction
A reaction in which an atom or a group of atoms is replaced by another atom or group of atoms.
Supercooled Liquids
Liquids that, when cooled, apparently solidify but actually continue to flow very slowly under the influence of gravity.
Supercritical Fluid
A substance at temperature above its critical temperature.
Supersaturated Solution
A solution that contains a higher than saturation concentration of solute; slight disturbance or seeding causes crystallization of excess solute.
Suspension
A heterogeneous mixture in which solute-like particles settle out of solvent-like phase some time after their introduction.


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