Attempts to discover order in nature and use that knowledge to make predictions about what is likely to happen in nature.
Factual information collected by scientists.
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.
An educated guess that attempts to explain a scientific law or certain scientific observations.
Approximate representation or simulation of a system being studied.
A well-tested and widely accepted scientific hypothesis.
Process of scientists reporting details of the methods and models they used, the results of their experiments, and the reasoning behind their hypotheses for other scientists working in the same field (their peers)to examine and criticize.
Using specific observations and measurements to arrive at a general conclusion or hypothesis.
Use of logic to arrive at a specific conclusion based on a generalization or premise.
Description of what scientists find happening in nature repeatedly in the same way, without known exception.
Law Of Nature (Scientific Law)
Description of what scientists find happening in nature repetadly in the same way, without known exception.
Shift in thinking that occurs when the majority of scientists in a field or related fields agree that a new explanation or theory is better than the old one.
Preliminary scientific data, hypotheses, and models that have not been widely tested and accepted.
Concepts and ideas that are widely accepted by experts in a particular field of the natural or social sciences.
Scientific results or hypotheses presented as reliable science but not having undergone the rigors of the peer review process
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.
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. Two or more elements combine to form the compounds that make up most of the world's matter.
Combination of atoms, or oppositely charged ions, of two or more elements held together by attractive forces called chemical bonds. Examples are NaCl, CO2, and C6H12O6.
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.
Idea that all elements are made up of atons; the most widely accepted scientific theory in chemistry.
Positively charged particle in the nuclei of all atoms. Each proton has a relative mass of 1 and a single positive charge.
Elementary particle in the nuclei of all atoms (except hydrogen-1). It has a relative mass of 1 and no electric charge.
Tiny particle moving around outside the nucleus of an atom. Each electron has one unit of negative charge and almost no mass.
Number of protons in the nucleus of an atom.
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 the atom.
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.
Numeric value that indicates the relative acidity or alkalinity of a substance on a scale of 0 to 14, with the neutral point at 7. Acid solutions have pH values lower than 7; basic or alkaline solutions have pH values greater than 7.
Combination of two or more atoms of the same chemical element (such as O2) or different chemical elements (such as H2O) held together by chemical bonds.
Shorthand way to show the number of atoms (or ions) in the basic structural unit of a compound. Examples include H2O, NaCl, and C6H12O6.
Compounds containing carbon atoms combined with each other and with atoms of a one or more other elements such as hydrogen, oxygen, nitrogen, sulfur, phosphorus, chlorine, and fluorine. All other compounds are called inorganic compounds.
All compounds not classified as organic compounds.
Smallest living unit of an organism. Each cell is encased in an outer membrane or wall and contains genetic material (DNA) and other parts to perform its life function. Organisms such as bacteria consist of only one cell, but most organisms contain many cells.
Coded units of information about specific traits that are passed from parents to offspring during reproduction. They consist of segments of DNA molecules found in chromosomes.
Characteristic passed on from parents to offspring during reproduction in an animal or plant.
A grouping of genes and associated proteins in plant and animal cells that carry certain types of genetic information.
Matter that is concentrated and contains a high concentration of a useful resource.
Measure of how useful a matter resource is, based on its availability and concentration.
Process that alters one or more physical properties of an element or a compound without changing its chemical composition. Examples include 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 frezing water).
One of the millions of different elements and compounds found naturally and synthesized by humans.
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.
Natural Radioactiv Decay
Nuclear changes in which unstable nuclei of atoms spontanously shoot out particles (usually alpha or beta particles) or energy (gamma rays) at a fixed rate
Radioactive Isotopes (Radioisotope)
Isotope of an atom that spontaneously emits one or more types of radioactiviry (alpha particles, beta particles, gamma rays).
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.
Multiple nuclear fissions, taking place within a certain mass of a fissionable isotope, which release an enormous amount of energy in a short time.
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.
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).
Capcity to do work by performing mechanical, physical, chemical, or electrical tasks or to cause a heat transfer between two objects at different temperatures.
Energy that matter has because of its mass and speed, or velocity.
Total kinetic energy of all randomly moving atoms, ions, or molecules within a given substance, excluding the overall motion of the whole object. Heat always flows spontaneously from a warmer sample of matter to a colder sample of matter. This is one way to state the second law of thermodynamics.
Forms of kinetic energy traveling as electromagnetic waves. Examples include radio waves, TV waves, microwaves, infrared radiation, visible light, ultraviolet radiation, Xrays, and gamma rays.
Energy stored in an object because of its position or the position of its parts.
Ability of a form of energy to do useful work. High-temperature heat and chemical energy in fossil fuels and nuclear fuels are concentrated high-quality energy. Low-quality energy suchas low-temperature heat is dispersed or diluted and cannot do much useful work.
Energy that is concentrated and has great ability to perform useful work. Examples include high-temperature heat and the energy in electricity, coal, oil, hasoline, sunlight, and nuclei of uranium-235.
Energy that is dispersed and has little ability to do useful work. An example is low-temperature heat.
First Law Of Thermodynamics
In any physical or chemical change, no detectable amount of energy is created or destroyed, but energy can be changed from one form to another; you cannot get more energy out of something than you put in; in terms of energy quantity. You cannot get something for nothing.This law does not apply to nuclear changes, in which energy can apply to nuclear changes, in whcih energy can be produced from small amounts of matter.
Second Law Of Thermodynamics
In any conversion of heat energy to useful work, some of the initial energy input is always degraded to lower-quality , more dispersed, less useful energy - usuallylow-temperature heat that flows into the environment; you cannot break even in terms of energy quality.
Percentage of the total energy input that does useful work and is not converted into low-quality, generally useless heat in an energy conversion system or process.
Rate of flow of matter, energy, or information through a system.
Matter, energy, or information entering a system.
Matter, energy, or information leaving a system.
Set of components that function and interact in some regular and theoretically predictable manner.
Any process that increases (positive feedback) or decreases (negative feedback) a change to a system.
Occurs when an output of matter, energy, or information is fed back into the system as an input and leads to changes in that system.
Positive Feedback Loop
Feedback loop that causes a system to change further in the same direction.
Negative Feedback Loop
Feedback loop that causes a system to change in the opposite direction from which is it moving.
Threshold level at whcih an environmental problem causes a fundamental and irreversible shift in the behavior of a system
Synergistic Interaction (Synergy)
Interaction of two or more factors or processes so that the combined effect is greater than the sum of their separate effects.