final chapter 1

PM10
particulate matter with an average diameter of 10 um or less
pm2.5
particulate matter with an average diameter less than 2.5 um, also called fine particles.
micrometer
a millionth(10^-6) of a meter sometimes simply refered to as a micron.
criteria air pollutants
air pollutants for which EPA has set permissible levels based on their effects on human health and on the environment
mixture
physical combination of two or more substances present in variable amounts
(See page(s) 11)
percent
parts per hundred; sometimes abbreviated as pph
(See page(s) 11, 201)
parts per million (ppm)
1 part out of a million parts, unit of concentration. 1 ppm is 10,000 times less concentrated than 1 part per hundred (pph).
(See page(s) 13, 201)
EPA air quality index
table 1.3 on page 15
risk assessment
organized evaluation of scientific data to predict the probability of an occurrence
(See page(s) 17)
toxicity
intrinsic health hazard of a substance
(See page(s) 17)
exposure
amount of a substance encountered, generally in reference to human contact with a toxic substance or a disease-causing organism
(See page(s) 17)
microgram (µg)
a millionth (10-6) of a gram
(See page(s) 18)
ambient air
the outside air, that is, the air surrounding or encircling us
(See page(s) 18)
parts per billion (ppb)
1 part out of a billion parts, unit of concentration. 1 ppb is 1000 times less concentrated than 1 ppm.
(See page(s) 19, 202)
troposphere
region of the atmosphere that lies directly above the surface of the Earth
(See page(s) 20)
stratosphere
region of the atmosphere above the troposphere; includes the ozone layer
(See page(s) 20)
mesosphere
region of the atmosphere above the stratosphere; found at an altitude starting about 50 km
(See page(s) 20)
element
pure substance that cannot be broken down into simpler ones by any chemical means
(See page(s) 21)
chemical symbol
one- or two-letter abbreviation for an element. Also called atomic symbol
(See page(s) 21)
periodic table
an orderly arrangement of all the elements based on similarities in their properties
(See page(s) 22)
group
vertical column in the periodic table
(See page(s) 23)
metals
elements that are shiny and conduct electricity and heat well. They tend to lose their valence electrons to form cations.
(See page(s) 23, 210)
nonmetals
elements with varied appearances that do not conduct electricity or heat well. Nonmetals tend to gain electrons to form anions.
(See page(s) 23, 210)
metalloids
elements between metals and nonmetals on the periodic table that do not fall cleanly into either group. Sometimes called semimetals.
(See page(s) 23)
noble gases
elements that are inert and do not readily undergo chemical reactions
(See page(s) 24)
compound
pure substance made up of two or more elements in a fixed, characteristic chemical combination
(See page(s) 24)
atom
smallest unit of an element that can exist as a stable, independent entity
(See page(s) 25)
nanotechnology
technology at the atomic and molecular (nanometer) scale: 1 nanometer (nm) =1 ?10-9 m
(See page(s) 25)
molecule
two or more atoms held together by chemical bonds in a certain spatial arrangement
(See page(s) 26)
chemical formula
symbolic way to represent the elementary composition of a substance, indicating the kinds and numbers of atoms present in a molecule
(See page(s) 26, 408)
diatomic molecule
molecule that contains two atoms
(See page(s) 26)
hydrocarbon
compound that contains only the elements hydrogen and carbon
(See page(s) 28, 171)
combustion
chemical process in which a fuel combines rapidly with oxygen to release energy and form products
(See page(s) 29,158)
chemical reaction
process whereby reactants are transformed into products
(See page(s) 29)
reactant
starting material that is transformed into a product during a chemical reaction
(See page(s) 29)
product
substance formed from reactants as a result of a chemical reaction
(See page(s) 29)
chemical equation
representation of a chemical reaction using chemical formulas
(See page(s) 29)
law of conservation of matter and mass
in a chemical reaction, matter and mass are conserved
(See page(s) 30)
aerosols
particles, both liquid and solid, that remain suspended in the air rather than settling out
(See page(s) 35)
catalytic converter
device installed in the exhaust stream of an engine to reduce emissions
(See page(s) 36)
catalyst
chemical substance that participates in a chemical reaction and influences its rate or speed without undergoing permanent change
(See page(s) 36, 84)
volatile
refers to a substance that readily passes into the vapor phase
(See page(s) 36)
organic compound
compound that contains mainly carbon and hydrogen
(See page(s) 36)
volatile organic compounds (VOCs)
vapors of incompletely burned gasoline molecules or fragments of these molecules
(See page(s) 37)
green chemistry
the designing of chemical products and processes that reduce or eliminate the use or generation of hazardous substances
(See page(s) 38)
secondary pollutant
pollutant produced from chemical reactions among two or more other pollutants
(See page(s) 40)
carcinogenic
capable of causing cancer
(See page(s) 43)
significant figure
a number that correctly represents the accuracy with which an experimental quantity is known
(See page(s) 46)