Chemistry

Diatomic Molecule

a molecule consisting of two atoms

mixture

a physical combination of two or more pure substances present in variable amounts

chemical reaction

a process whereby substances described as reactants are transformed into different substances called products

Respiration

the foods we eat are metabolized to produce carbon dioxide and water

Megacities

urban areas with 10 million people or more

Metalloids

Elements that lie between metals and nonmetals on the periodic table and do not fall cleanly into either category

Microgram

a millionth of a gram of 10^-6

Chemical Formula

a symbolic way to represent the elementary composition of a substance

Periodic Table

an orderly arrangement of all the elements based on similarities in their properties

Aerosols

are liquids and solid particles that remain suspended in the air rather than settling out

Coalescents

chemicals added to soften the latex particles in paint so that these particles spread to form a continuos film of uniform thickness

Metals

elements that are shiny and conduct electricity and heat well

Pm2.5

is a subset of PM10 and includes particles with an average diameter of less than 2.5ums

Chemical Symbols

on or two letter abbreviations for the elements

Parts per billion ppb

on part out of one billion or 1000 times less concentrated than one part per million

Element

one of the 100 or so pure substances in our world from which compounds are formed

Noble Gas

one of the inert elements in Group 8A that undergoes few, if any, chemical reactions

What does percent meant?

parts per hundred

Ambient Air

the air surrounding us, usually meaning the outside air

Combustion

the chemical process of burning; that is, the rapid combination of fuel with oxygen to release energy in the form of heat and light

Toxicity

the intrinsic health hazard of a substance

Troposphere

the lower region of the atmosphere in which we live that lies directly above the surface of the Earth

Atom

the smallest unit of an element that can exist as a stable, independent entity.

Molecule

two or more atoms held together by chemical bonds in a certain spatial arrangement

Tragedy of the Commons

when a resource is common to all and used by many , but has no one in particular responsible for it. As a result, the resource may be destroyed by overuse to the detriment of all who use it

Catalyst

a chemical substance that participates in a chemical reaction and influences its rate without itself undergoing permanent change

Compound

a pure substance made up of two or more different elements in a fixed, characterized chemical combination

Chemical Equations

a representation of chemical reaction using chemical formulas

Scientific Notation

a system for writing numbers as the product of a number and 10 raised to the appropriate power

Organic Compound

always contains carbon, almost always contains hydrogen, and may contain elements such as oxygen and nitrogen

Carcinogenic

capable of causing cancer

Volatile Organic Compounds(VOCs)

carbon-containing compounds that pass easily into the vapor phase

Hydrocarbons

compounds made up only of the elements hydrogen and carbon

Significant Figure

digit that is included (or excluded) to correctly represent the accuracy with which an experimental quantity is known

Nonmetals

elements that do not conduct heat or electricity well and have no one characteristic appearance

Law of Conservation of matter and mass

in a chemical reaction, matter and mass are conserved

PM10

includes particles with an aberage diameter of 10 Um or less, a length on the order of 0.0004 inches

Secondary Pollutant

it is produced from chemical reactions involving one more more other pollutants

Halogen

one of the reactive nonmetals in group 7A such as fluorine (F), Chlorine (Cl), Bromine (Br), or iodine (I).

groups

organize elements according to important properties that they have in common and are numbered from left to right

Volatile

readily passes into the vapor phase; tat is it evaporated easily

Nanotechnology

refers to the creation of materials at the atomic and molecular (nanometer) scale: 1 nanometer (nm)= 1 X 10 ^ -9 m

Exposure

the amount of the substance encountered

Risk Assessment

the process of evaluating scientific data and making predictions in an organized manner about the probabilities of an outcome