Glossary
Chapter 3
acid	See acid solution.
alpha particle	Positively charged matter, consisting of two neutrons and two protons, that is emitted as a form of radioactivity from the nuclei of some radioisotopes. See also beta particle, gamma rays.
atom	Minute unit made of subatomic particles that is the basic building block of all chemical elements and thus all matter; the smallest unit of an element that can exist and still have the unique characteristics of that element. Compare ion, molecule.
atomic number	Number of protons in the nucleus of an atom. Compare mass number.
beta particle	Swiftly moving electron emitted by the nucleus of a radioactive isotope. See also alpha particle, gamma rays.
biodegradable pollutant	Material that can be broken down into simpler substances (elements and compounds) by bacteria or other decomposers. Paper and most organic wastes such as animal manure are biodegradable but can take decades to biodegrade in modern landfills. Compare degradable pollutant, nondegradable pollutant, slowly degradable pollutant.
chain reaction	Multiple nuclear fissions, taking place within a certain mass of a fissionable isotope, that release an enormous amount of energy in a short time.
chemical	One of the millions of different elements and compounds found naturally and synthesized by humans. See compound, element.
chemical change	Interaction between chemicals in which there is a change in the chemical composition of the elements or compounds involved. Compare nuclear change, physical change.
chemical formula	Shorthand way to show the number of atoms (or ions) in the basic structural unit of a compound. Examples are H₂O, NaCl, and C₆H₁₂O₆.
chemical reaction	See chemical change.
chlorinated hydrocarbon	Organic compound made up of atoms of carbon, hydrogen, and chlorine. Examples are DDT and PCBs.
compound	Combination of atoms, or oppositely charged ions, of two or more different elements held together by attractive forces called chemical bonds. Compare element.
concentration	Amount of a chemical in a particular volume or weight of air, water, soil, or other medium.
consensus science	Scientific data, models, theories, and laws that are widely accepted by scientists considered experts in the area of study. These results of science are very reliable. Compare frontier science.
critical mass	Amount of fissionable nuclei needed to sustain a nuclear fission chain reaction.
DDT	Dichlorodiphenyltrichloroethane, a chlorinated hydrocarbon that has been widely used as a pesticide but is now banned in some countries.
degradable pollutant	Potentially polluting chemical that is broken down completely or reduced to acceptable levels by natural physical, chemical, and biological processes. Compare biodegradable pollutant, nondegradable pollutant, slowly degradable pollutant.
electromagnetic radiation	Forms of kinetic energy traveling as electromagnetic waves. Examples are radio waves, TV waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X rays, and gamma rays. Compare ionizing radiation, nonionizing radiation.
electron (e)	Tiny particle moving around outside the nucleus of an atom. Each electron has one unit of negative charge and almost no mass. Compare neutron, proton.
element	Chemical, such as hydrogen (H), iron (Fe), sodium (Na), carbon (C), nitrogen (N), or oxygen (O), whose distinctly different atoms serve as the basic building blocks of all matter. There are 92 naturally occurring elements. Another 23 have been made in laboratories. Two or more elements combine to form compounds that make up most of the world's matter. Compare compound.
energy	Capacity to do work by performing mechanical, physical, chemical, or electrical tasks or to cause a heat transfer between two objects at different temperatures.
energy productivity	See energy efficiency.
energy quality	Ability of a form of energy to do useful work. High-temperature heat and the chemical energy in fossil fuels and nuclear fuels are concentrated high-quality energy. Low-quality energy such as low-temperature heat is dispersed or diluted and cannot do much useful work. See high-quality energy, low-quality energy.
feedback loop	Circuit of sensing, evaluating, and reacting to changes in environmental conditions as a result of information fed back into a system; it occurs when one change leads to some other change, which eventually reinforces or slows the original change. See negative feedback loop, positive feedback loop.
first law of energy	See first law of thermodynamics.
first law of thermodynamics	In any physical or chemical change, no detectable amount of energy is created or destroyed, but in these processes energy can be changed from one form to another; you can't get more energy out of something than you put in; in terms of energy quantity, you can't get something for nothing (there is no free lunch). This law does not apply to nuclear changes, in which energy can be produced from small amounts of matter. See also second law of thermodynamics.
flows	See throughputs
frontier science	Preliminary scientific data, hypotheses, and models that have not been widely tested and accepted. Compare consensus science.
gamma rays	A form of ionizing electromagnetic radiation with a high energy content emitted by some radioisotopes. They readily penetrate body tissues. See also alpha particle, beta particle.
genes	Coded units of information about specific traits that are passed on from parents to offspring during reproduction. They consist of segments of DNA molecules found in chromosomes.
half-life	Time needed for one-half of the nuclei in a radioisotope to emit its radiation. Each radioisotope has a characteristic half-life, which may range from a few millionths of a second to several billion years. See radioisotope.
heat	Total kinetic energy of all the randomly moving atoms, ions, or molecules within a given substance, excluding the overall motion of the whole object. Heat always flows spontaneously from a hot sample of matter to a colder sample of matter. This is one way to state the second law of thermodynamics. Compare temperature.
high-quality energy	Energy that is concentrated and has great ability to perform useful work. Examples are high-temperature heat and the energy in electricity, coal, oil, gasoline, sunlight, and nuclei of uranium-235. Compare low-quality energy.
high-quality matter	Matter that is concentrated and contains a high concentration of a useful resource. Compare low-quality matter.
high-throughput economy	The situation in most advanced industrialized countries, in which ever-increasing economic growth is sustained by increasing the rate at which matter and energy resources are used, with little emphasis on pollution prevention, recycling, reuse, reduction of unnecessary waste, and other forms of resource conservation. Compare low-throughput economy, matter-recycling economy.
hydrocarbon	Organic compound of hydrogen and carbon atoms. The simplest hydrocarbon is methane (CH₄), the major component of natural gas.
inorganic compounds	All compounds not classified as organic compounds. See organic compounds.
input	Matter, energy, or information entering a system. Compare output, throughput.
ion	Atom or group of atoms with one or more positive (1) or negative (2) electrical charges. Compare atom, molecule.
ionizing radiation	Fast-moving alpha or beta particles or high-energy radiation (gamma rays) emitted by radioisotopes. They have enough energy to dislodge one or more electrons from atoms they hit, forming charged ions in tissue that can react with and damage living tissue. Compare nonionizing radiation.
isotopes	Two or more forms of a chemical element that have the same number of protons but different mass numbers because they have different numbers of neutrons in their nuclei.
kinetic energy	Energy that matter has because of its mass and speed or velocity. Compare potential energy.
law of conservation of energy	See first law of thermodynamics.
law of conservation of matter	In any physical or chemical change, matter is neither created nor destroyed but merely changed from one form to another; in physical and chemical changes, existing atoms are rearranged into different spatial patterns (physical changes) or different combinations (chemical changes).
low-quality energy	Energy that is dispersed and has little ability to do useful work. An example is low-temperature heat. Compare high-quality energy.
low-quality matter	Matter that is dilute or dispersed or contains a low concentration of a useful resource. Compare high-quality matter.
low-throughput economy	Economy based on working with nature by (1) recycling and reusing discarded matter, (2) preventing pollution, (3) conserving matter and energy resources by reducing unnecessary waste and use, (4) not degrading renewable resources, (5) building things that are easy to recycle, reuse, and repair, (6) not allowing population size to exceed the carrying capacity of the environment, and (7) preserving biodiversity. See environmental worldview. Compare high-throughput economy, matter-recycling economy.
low-waste society	See low-throughput economy.
mass	The amount of material in an object.
mass number	Sum of the number of neutrons (n) and the number of protons (p) in the nucleus of an atom. It gives the approximate mass of that atom. Compare atomic number.
material efficiency	Total amount of material needed to produce each unit of goods or services. Also called resource productivity. Compare energy efficiency.
matter	Anything that has mass (the amount of material in an object) and takes up space. On the earth, where gravity is present, we weigh an object to determine its mass.
matter quality	Measure of how useful a matter resource is, based on its availability and concentration. See high-quality matter, low-quality matter.
mixture	Combination of one or more elements and compounds.
model	An approximate representation or simulation of a system being studied.
molecule	Combination of two or more atoms of the same chemical element (such as O₂) or different chemical elements (such as H,sub>2O) held together by chemical bonds. Compare atom, ion.
natural ionizing radiation	Ionizing radiation in the environment from natural sources.
natural law	See scientific law.
natural radioactive decay	Nuclear change in which unstable nuclei of atoms spontaneously shoot out particles (usually alpha or beta particles) or energy (gamma rays) at a fixed rate.
negative feedback loop	Situation in which a change in a certain direction provides information that causes a system to change less in that direction. Compare positive feedback loop.
neutral solution	Water solution containing an equal number of hydrogen ions (H⁺) and hydroxide ions (OH^-); water solution with a pH of 7. Compare acid solution, basic solution.
neutron (n)	Elementary particle in the nuclei of all atoms (except hydrogen-1). It has a relative mass of 1 and no electric charge. Compare electron, proton.
nondegradable pollutant	Material that is not broken down by natural processes. Examples are the toxic elements lead and mercury. Compare biodegradable pollutant, degradable pollutant, slowly degradable pollutant.
nonionizing radiation	Forms of radiant energy such as radio waves, microwaves, infrared light, and ordinary light that do not have enough energy to cause ionization of atoms in living tissue. Compare ionizing radiation.
nonpersistent pollutant	See degradable pollutant.
nuclear change	Process in which nuclei of certain isotopes spontaneously change, or are forced to change, into one or more different isotopes. The three principal types of nuclear change are natural radioactivity, nuclear fission, and nuclear fusion. Compare chemical change, physical change.
nuclear fission	Nuclear change in which the nuclei of certain isotopes with large mass numbers (such as uranium-235 and plutonium-239) are split apart into lighter nuclei when struck by a neutron. This process releases more neutrons and a large amount of energy. Compare nuclear fusion.
nucleus	Extremely tiny center of an atom, making up most of the atom's mass. It contains one or more positively charged protons and one or more neutrons with no electrical charge (except for a hydrogen-1 atom, which has one proton and no neutrons in its nucleus).
organic compounds	Compounds containing carbon atoms combined with each other and with atoms of one or more other elements such as hydrogen, oxygen, nitrogen, sulfur, phosphorus, chlorine, and fluorine. All other compounds are called inorganic compounds.
output	Matter, energy, or information leaving a system. Compare input, throughput.
parts per billion (ppb)	Number of parts of a chemical found in 1 billion parts of a particular gas, liquid, or solid.
parts per million (ppm)	Number of parts of a chemical found in 1 million parts of a particular gas, liquid, or solid.
parts per trillion (ppt)	Number of parts of a chemical found in 1 trillion parts of a particular gas, liquid, or solid.
PCBs	See polychlorinated biphenyls.
persistent pollutant	See slowly degradable pollutant.
physical change	Process that alters one or more physical properties of an element or a compound without altering its chemical composition. Examples are changing the size and shape of a sample of matter (crushing ice and cutting aluminum foil) and changing a sample of matter from one physical state to another (boiling and freezing water). Compare chemical change, nuclear change.
pollutant	A particular chemical or form of energy that can adversely affect the health, survival, or activities of humans or other living organisms. See pollution.
polychlorinated biphenyls (PCBs)	Group of 209 different toxic, oily, synthetic chlorinated hydrocarbon compounds that can be biologically amplified in food chains and webs.
positive feedback loop	Situation in which a change in a certain direction provides information that causes a system to change further in the same direction. Compare negative feedback loop.
potential energy	Energy stored in an object because of its position or the position of its parts. Compare kinetic energy.
ppb	See parts per billion.
ppm	See parts per million.
ppt	See parts per trillion.
prokaryotic cell	Cell that doesn't have a distinct nucleus. Other internal parts are also not enclosed by membranes. Compare eukaryotic cell.
pyramid of energy flow	Diagram representing the flow of energy through each trophic level in a food chain or food web. With each energy transfer, only a small part (typically 10%) of the usable energy entering one trophic level is transferred to the organisms at the next trophic level. Compare pyramid of biomass, pyramid of numbers.
radioactive isotope	See radioisotope.
reserve-to-production ratio	Number of years reserves of a particular nonrenewable mineral will last at current annual production rates. See reserves.
salinization	Accumulation of salts in soil that can eventually make the soil unable to support plant growth.
saltwater intrusion	Movement of salt water into freshwater aquifers in coastal and inland areas as groundwater is withdrawn faster than it is recharged by precipitation.
sanitary landfill	Waste disposal site on land in which waste is spread in thin layers, compacted, and covered with a fresh layer of clay or plastic foam each day.
scavenger	Organism that feeds on dead organisms that were killed by other organisms or died naturally. Examples are vultures, flies, and crows. Compare detritivore.
science	Attempts to discover order in nature and use that knowledge to make predictions about what should happen in nature. See consensus science, frontier science, scientific data, scientific hypothesis, scientific law, scientific methods, scientific model, scientific theory.
scientific data	Facts obtained by making observations and measurements. Compare scientific hypothesis, scientific law, scientific methods, scientific model, scientific theory.
scientific hypothesis	An educated guess that attempts to explain a scientific law or certain scientific observations. Compare scientific data, scientific law, scientific methods, scientific model, scientific theory.
scientific law	Description of what scientists find happening in nature repeatedly in the same way, without known exception. See first law of thermodynamics, law of conservation of matter, second law of thermodynamics. Compare scientific data, scientific hypothesis, scientific methods, scientific model, scientific theory.
secondary pollutant	Harmful chemical formed in the atmosphere when a primary air pollutant reacts with normal air components or other air pollutants. Compare primary pollutant.
secondary sewage treatment	Second step in most waste treatment systems in which aerobic bacteria break down up to 90% of degradable, oxygen-demanding organic wastes in wastewater. This usually involves bringing sewage and bacteria together in trickling filters or in the activated sludge process. Compare advanced sewage treatment, primary sewage treatment.
shelterbelt	See windbreak.
stream	Flowing body of surface water. Examples are creeks and rivers.
subatomic particles	Extremely small particlesQelectrons, protons, and neutronsQthat make up the internal structure of atoms.
sustainable living	Taking no more potentially renewable resources from the natural world than can be replenished naturally and not overloading the capacity of the environment to cleanse and renew itself by natural processes.
synergistic interaction	Interaction of two or more factors or processes so that the combined effect is greater than the sum of their separate effects.
synthetic natural gas (SNG)	Gaseous fuel containing mostly methane produced from solid coal.
thermal inversion	See temperature inversion.
thermocline	Zone of gradual temperature decrease between warm surface water and colder deep water in a lake, reservoir, or ocean.
threatened species	Wild species that is still abundant in its natural range but is likely to become endangered because of a decline in numbers. Compare endangered species.
DNA (deoxyribonucleic acid)	Large molecules in the cells of organisms that carry genetic information in living organisms.
sustainable development	See environmentally sustainable economic development.
acid solution	Any water solution that has more hydrogen ions (H⁺) than hydroxide ions (OH^-); any water solution with a pH less than 7. Compare basic solution, neutral solution.
nuclear energy	Energy released when atomic nuclei undergo a nuclear reaction such as the spontaneous emission of radioactivity, nuclear fission, or nuclear fusion.
nuclear fusion	Nuclear change in which two nuclei of isotopes of elements with a low mass number (such as hydrogen-2 and hydrogen-3) are forced together at extremely high temperatures until they fuse to form a heavier nucleus (such as helium-4). This process releases a large amount of energy. Compare nuclear fission.
energy efficiency	Percentage of the total energy input that does useful work and is not converted into low-quality, usually useless heat in an energy conversion system or process. See energy quality, net energy. Compare material efficiency.
matter-recycling economy	Economy that emphasizes recycling the maximum amount of all resources that can be recycled. The goal is to allow economic growth to continue without depleting matter resources and without producing excessive pollution and environmental degradation. Compare high-throughput economy, low-throughput economy.
experiment	Procedure a scientist uses to study some phenomenon under known conditions. Scientists conduct some experiments in the laboratory and others in nature. The resulting scientific data or facts must be verified or confirmed by repeated observations and measurements, ideally by several different investigators.
biodegradable	Capable of being broken down by decomposers.
temperature	Measure of the average speed of motion of the atoms, ions, or molecules in a substance or combination of substances at a given moment. Compare heat.
chromosome	A grouping of various genes and associated proteins in plant and animal cells that carry certain types of genetic information. See genes.
persistence	How long a pollutant stays in the air, water, soil, or body. See also inertia.
calorie	Unit of energy; amount of energy needed to raise the temperature of 1 gram of water 1!C (unit on Celsius temperature scale). See also kilocalorie.
kilocalorie (kcal)	Unit of energy equal to 1,000 calories. See calorie.