CHEM 105 Chp. 1-2

Chemical symbols

1 or 2 letter abbreviations for the elements

Significant figures

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

Microgram

a millionth of a gram (g), or 10^-6g

Diatomic molecule

a molecule consisting of two atoms

Mixture

a physical combinations of two or more pure substances present in variable form

Chemical reaction

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

Chemical equation

a representation of a chemical reaction using chemical formulas

Green Chemistry

a set of principles to guide all in the chemical community . It is 'benign by design. Calls for designing chemical products and processes that reduce or eliminate the use or generation of hazardous substances.

Chemical arrangement

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

Volatile organic compounds (VOC's)

carbon-containing compounds that pass easily into the vapor phase

Coalescents

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

Metalloids (semimetals)

elements that lie between metals and nonmetals on the periodic table and do not fall cleanly into either category. Only 8 elements fall into this category.

Aerosols

liquid and solid particles that remain suspended in the air rather than settling out. (smoke)

Halogen

one of the reactive nonmetals in group 7A (Fluorine, Chlorine, Bromine, Iodine)

Parts per billion (ppb)

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

Nanotechnology

refers to the creation of materials at the atomic and molecular (nanometer) scale: 1 nanometer (nm)=1x10^-9

Exposure

the amount of a substance encountered

Respiration

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

Shifting baselines

the idea that what people expect as "normal" on our planet has changed over time, especially with regard to ecosystems

Risk Assessment

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

Groups

vertical columns on the periodic table. Numbered from left to right

Law of conservation of matter and mass

In a chemical reaction, matter and mass are conserved. The mass of the reactants consumed equals the mass of the products formed

Parts per million (ppm)

One ppm is a unit 10,000 times smaller than 1% (one part per hundred)

Catalyst

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

Compound

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

Scientific notation

a system for writing numbers as the product of a number 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

Hydrocarbons

compounds made up only of the elements hydrogen and carbon

Metals

elements that ares shiny and conduct electricity and heat well (iron, gold, copper)

Nonmetals

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

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.

Secondary pollutant

produced from chemical reactions involving one or more other pollutants

Volatile

substance readily passes into the vapor phase; that is, it evaporates easily (gasoline, nail polish remover)

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

Atoms

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.

Megacities

urban ares with 10 million people or more

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 resources may be destroyed by overuse to the detriment of all who use it.