Glossary of Terms

Safety matches
These matches can only be lit by striking on the specially prepared abrasive surface on the side of the matchbox, while "strike-anywhere" matches (illegal in many countries because of fire hazard) can be struck on any rough surface.
The heads of safety matches contain sulfur and oxidizing agents such as potassium chlorate with powdered glass, fillers, colouring matter and a binder of glue and starch. The striking surface on the box contains red phosphorus, powdered glass or silica (sand), filler and binder. When the match is struck, the heat from the friction causes a small amount of red phosphorus on the box to be vapourized as white phosphorus vapour. The latter burns spontaneously in air and initiates the decomposition of the potassium chlorate which liberates oxygen. The sulfur ignites and lights the wood of the match.
The heads of strike-anywhere matches contain phosphorus sulphide P₄S₃, oxidizing agents, powdered glass to increase the friction and a glue as a binder. Since both phosphorus and sulfur are present on the heads of the strike-anywhere matches, striking these matches anywhere will generate enough heat of friction to ignite the phosphorus sulfide. The train of reactions thereafter is similar to that which is described above.
Salt
An ionic compound made up of a cation and an anion. It is often produced in neutralizaion reactions.
Scientific Notation
A systematic way of expressing a number in exponential notation. The format is

#.### x 10^#
Semimetals
Also called metalloids, are elements that have both metallic and nonmetallic properties.
These are:
- B, Si, Ge, As, Sb, Te, Po, At
The semimetals are positioned next to the diagonal line on the periodic table, between the metals, and the nonmetals.

SI unit

The system of units used universally for expressing all measured quantites is Le Système International d'Unités (The International System of Units). Some SI units are:

Physical quantity	Units	Symbol
length	meter	m
mass	kilogram	kg
time	second	s
temperature	kelvin	K
energy	joule	J
charge	coulomb	C

The following is a summary of some of the base units in the SI system. All base units except the kilogram are now defined by physical phenomena which can be measured anywhere in the universe. The kilogram is still defined by a unique artifact.

Base Unit	Origin
meter (m)	The distance light travels in a vacuum in 1/299 792 458 of a second.
kilogram (kg)	The mass of the International Prototype Kilogram, a small cylinder of platinum-iridium preserved in a vault in France.
second (s)	The duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium-133 atom (at a temperature of 0 K).
kelvin (K)	The fraction 1/273.16 of the thermodynamic temperature of the triple point of water.

Slaked lime
Slaked lime is an important material in the control of air pollution. It reacts with the SO₂ formed in the combustion of sulfur-containing coal. The product is a solid, calcium sulfite, CaSO₃, which cannot escape into the atmosphere.
Solvent extraction
If a substance is shaken with two immisicible liquids, upon standing, the two layers will separate and the substance will be distributed between the two liquid layers. A greater concentration of the substance will be present in that solvent in which it is more soluble.
Solvent extraction is an industrial method of removing impurities from liquids and in separating pure metals from their ores.
Spectroscopy
Spectroscopy is a branch of analytical chemistry devoted to the determination of structure of atoms and the chemical composition of molecules by measuring the radiant energy they absorb or emit in any of the wavelengths of the electromagnetic spectrum.
When atoms or molecules are excited electrically by an arc or spark, they emit electromagnetic radiation that is characteristic of their component atoms. An instrument for measuring the intensity of radiation at different wavelengths in a spectrum is called a spectrophotometer.
Standard Temperature and Pressure (STP)

standard temperature is 273 K (or 0 ^oC).

standard pressure is 1 atm (760 torr)
Stone Age
The earliest known period of human culture, marked by the use of stone tools.
Sublimation
Direct transition to the gaseous state from the solid state without passing through the liquid state.
Substance
A substance has constant composition and properties throughout. All substances are either elements or compounds.
Superconductor
A material that has zero bulk electrical resistance. Most superconductors only exhibit this behaviour at extremely low temperatures (< 10 K). In the late 80s, scientists discovered a new class of high temperature of superconducting material that can remaining superconducting up to approximately 80 to 100K.
Superphosphate
The most important agricultural source of phosphorus. Naturally-occurring rock phosphate consists essentially of calcium phosphate, Ca₃(PO₄)2, is almost insoluble in water. Before it can be applied to soils and made readily available for plants, treatment with sulfuric acid converts the rock phosphate to the more soluble form, a mixture of dihydrogen phosphate and hydrated calcium sulfate, gypsum (Ca(H₂PO₄)₂ and CaSO₄.2H₂O). This mixture is sold as superphosphate.
Teflon
Teflon,a trademark for a waxy, opague material. It is a very unreactive plastic consisting of polymers of -CF₂-CF₂- units. It is used as a coating on cooking utensils and in industrial applications to prevent sticking.
Thermocouple
A very accurate device for measuring temperature by use of two dissimilar metals (usually in wire form) in fused contact. The junction develops a measurable electric potential which varies with change of temperature.
Different sets of dissimilar metals can be used over a range of from subzero temperatures to those above 2000^oC.
TNT
Trinitrotoluene is a highly unstable solid that is used as an explosive.
Tooth decay
Tooth enamel consists of hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂). If a reasonable level of fluoride ion is present in the diet during the growing phase of teeth, a significant amount of fluoroapatite (Ca₁₀(PO₄)₆F₂), is incorporated in the enamel in place of the hydroxyapatite. Fluoroapatite is less soluble in mouth acids, hence fluoride-containing teeth are less susceptible to decay.
Many communities recommend a fluoride supplement for growing children. About half the population of the U.S. and Canada drinks artificially fluoridated water. Sodium fluoride is added to public water supplies in carefully regulated, nontoxic amounts.
It should be told that too much fluoride is also harmful. It discolours teeth and it accumulates in the bones, causing pain and possible crippling.
Transferium elements
Elements which have atomic numbers greater than 100. They are:

Element Name and Symbol Atomic Number

Mendelevium, Md 101

Nobelium, No 102

Lawrencium, Lr 103

Rutherfordium, Rf 104

Dubnium, Db 105

Seaborgium, Sg 106

Bohrium, Bh 107

Hassium, Hs 108

Meitnerium, Mt 109

standard temperature is 273 K (or 0 ^oC).
standard pressure is 1 atm (760 torr)

Element Name and Symbol	Atomic Number
Mendelevium, Md	101
Nobelium, No	102
Lawrencium, Lr	103
Rutherfordium, Rf	104
Dubnium, Db	105
Seaborgium, Sg	106
Bohrium, Bh	107
Hassium, Hs	108
Meitnerium, Mt	109

Transuranium elements

Elements which have atomic numbers greater than 92. They are:

Element Name and Symbol	Atomic Number
Neptunium, Np	93
Plutonium, Pu	94
Americium, Am	95
Curium, Cm	96
Berkelium, Bk	97
Californium, Cf	98
Einsteinium, Es	99
Fermium, Fm	100
Mendelevium, Md	101
Nobelium, No	102
Lawrencium, Lr	103

Type Metal
An alloy consisting chiefly of tin, lead, and antimony, used for making metal printing type.
Units
The units of a measurement indicates the standard against which the measured quantity is compared. In Chemistry, the units for:
- length is meter
- mass is gram
- volume is liter
Valence electrons
The electrons in the outermost energy level of an atom. The number of valence electrons vary from 1 to 8. These are the electrons that participate in chemical bonding.
Vector
Vectors are quantities that can be described when both their magnitude and direction are specified. Examples of vectors are velocity, force and momentum.
Dipole moment is also a vector quantity.
Work
In science, work is a measure of the transfer of energy. It is expressed as a force acting through a distance.

work = (force) x (distance)

The unit of work can be in joules or calories.

Zeolite

Zeolite is a member of a group of hydrated aluminosilicate minerals which occur in nature and are also manufactured for their ion exchange properties. They are crystalline compounds composed of silicon, oxygen and some aluminum atoms. The crystalline complex forms channels and cages of varying size which can exert an ionic selectivity or "sieving" effect when placed in a solutions containing ions.

All zeolite crystal structures is a framework built up by silicon and aluminum atoms (black) surrounded by 4 oxygen (white) atoms in "tetrahedral" configurations.

These linked tetrahedra form cage-like structures, with voids measuring several angstroms. Diameters of atoms range from approximately 1 to 4 angstroms.

Zeolite ion-exchange units are extensively used in water conditioning to remove calcium and magnesium ions by replacing them with sodium ions. These units can be regenerated by treatment with sodium chloride solutions.

Nowadays, a large number of different natural and synthetic zeolites are used for:

removal of radioactive elements from low-level waste streams of nuclear plants,
treatment of sewage by removing toxic ammonia compounds that kill fish and promote algae growth,
pollution control as an adsorbent in oil-spill cleanup,
purification of gas produced from sewage and decaying garbage,
energy production through the incorporation of zeolites as boosters in solar panels or heat reservoirs,
blood purification in dialysis machines.

Zone refining
In this process, a rod of metal is heated near one end so that a cross-sectional wafer of molten metal is produced. Since impurities are more soluble in the melt than they are in the solid they concentrate in the melt, and the melted zone is then caused to move slowly along the rod by moving the heat source. This carries impurities to the end. The process can be repeated and the impure end is then removed.
Super-pure (with impurities < 10^-9 atom per cent) of silicon and germanium are obtained by this process as high purity is required for the fabrication of semiconductors.

This page is part of the BCIT Chemistry Resource Center website.

All contents copyrighted © 1997 - 2004
 Chemistry Department
British Columbia Institute of Technology, Burnaby, B.C. Canada.
All Rights reserved

Safety matches

Salt

Scientific Notation

Semimetals

SI unit

Slaked lime

Solvent extraction

Spectroscopy

Standard Temperature and Pressure (STP)

Stone Age

Sublimation

Substance

Superconductor

Superphosphate

Teflon

Thermocouple

TNT

Tooth decay

Transferium elements

Transuranium elements

Type Metal

Units

Valence electrons

Vector

Work

Zeolite

Zone refining