acidity
a chemical characteristic that helps determine how a substance dissolved in water will interact with and affect its environment
atom
The most basic building block of matter is an atom: the smallest unit of matter into which an element can be divided and still retain its chemical properties.
atomic number
equal to the number of protons in the nucleus of its atom
atomic theory
the most widely accepted scientific theory in chemistry that states the idea that all elements are made up of atoms
cells
the fundamental structural units of life
chain reaction
Multiple fissions within a certain amount of mass produce a chain reaction, which releases an enormous amount of energy.
chemical change, or chemical reaction
In a chemical change, or chemical reaction, there is a change in the arrangement of atoms or ions within molecules of the substances involved.
chemical formula
Chemists use a chemical formula to show the number of each type of atom or ion in a compound.
chromosome
Thousands of genes, in turn, make up a single chromosome, a special DNA molecule together with a number of proteins.
compounds
combinations of two or more different elements held together in fixed proportions.
data
information needed to answer their questions�scientists make observations of the subject area they are studying.
deductive reasoning
involves using logic to arrive at a specific conclusion based on a generalization or premise.
electromagnetic radiation
another form of kinetic energy, energy travels in the form of a wave as a result of changes in electric and magnetic fields.
electrons (e)
negatively charged subatomic particles
elements
each of which is a fundamental substance that has a unique set of properties and cannot be broken down into simpler substances by chemical means.
energy
the capacity to do work or transfer heat. Work is done when something is moved.
Energy efficiency, or energy productivity
a measure of how much useful work is accomplished by a particular input of energy into a system.
energy quality
a measure of an energy source's capacity to do useful work
experiments
procedures carried out under controlled conditions to gather information and test ideas
feedback
any process that increases (positive feedback) or decreases (negative feedback) a change to a system.
feedback loop
a process that 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
genes
certain sequences of nucleotides within some DNA molecules
heat
Another form of kinetic energy is heat: the total kinetic energy of all moving atoms, ions, or molecules within a given substance.
high-quality energy
is concentrated and has a high capacity to do useful work.
high-quality matter
is highly concentrated, is typically found near the earth's surface, and has great potential for use as a resource.
inductive reasoning
involves using specific observations and measurements to arrive at a general conclusion or hypothesis.
inorganic compounds
Table sugar, vitamins, plastics, aspirin, penicillin, and most of the chemicals in your body are organic compounds, which contain at least two carbon atoms combined with atoms of one or more other elements. All other compounds are called inorganic compoun
inputs/flows or throughputs/outputs
Most systems have the following key components: inputs from the environment, flows or throughputs of matter and energy within the system at certain rates, and outputs to the environment.
ion
an atom or groups of atoms with one or more net positive or negative electrical charges (building block of matter)
isotopes
Forms of an element having the same atomic number but different mass numbers
kinetic energy
Moving matter has kinetic energy because it has mass and velocity.
law of conservation of energy
(first law of thermodynamics) When energy is converted from one form to another in a physical or chemical change, no energy is created or destroyed.
law of conservation of matter
when a physical or chemical change occurs, no atoms are created or destroyed.
low-quality energy
is dispersed and has little capacity to do useful work
mass number
the total number of neutrons and protons in its nucleus
matter
anything that has mass and takes up space
matter quality
a measure of how useful a form of matter is to humans as a resource, based on its availability and concentration, or amount of it that is contained in a given area or volume.
model
an approximate representation or simulation of a system being studied.
molecule
a combination of two or more atoms of the same or different elements held together by forces called chemical bonds (building block of matter)
natural radioactive decay
isotopes spontaneously emit fast-moving subatomic particles, high-energy radiation such as gamma rays, or both
negative, or corrective, feedback loop
causes a system to change in the opposite direction from which it is moving
neutrons (n)
a subatomic particle with no electrical charge
nuclear changes
changes in the nuclei of its atoms (3 types)
nuclear fission
a nuclear change in which the nuclei of certain isotopes with large mass numbers (such as uranium-235) are split apart into lighter nuclei when struck by neutrons; each fission releases two or three neutrons plus energy.
nuclear fusion
a nuclear change in which two isotopes of light elements, such as hydrogen, are forced together at extremely high temperatures until they fuse to form a heavier nucleus.
nucleus
an extremely small and dense center of an atom �which contains one or more protons and, in most cases, one or more neutrons.
organic compounds
contain at least two carbon atoms combined with atoms of one or more other elements (table sugar, vitamins, plastics, aspirin, penicillin, and most of the chemicals in your body)
paradigm shift
when new discoveries and new ideas overthrow a well-accepted scientific theory or law
peer review
happens when scientists report 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
pH
a measure of acidity, based on the amount of hydrogen ions (H+) and hydroxide ions (OH-) contained in a particular volume of a solution
physical change
when a sample of matter undergoes change but its chemical composition, or the arrangement of its atoms or ions within molecules, does not change
positive feedback loop
causes a system to change further in the same direction
potential energy
stored energy that is potentially available for use
protons (p)
positively charged subatomic particles
radioactive decay
occurs when nuclei of unstable isotopes spontaneously emit fast-moving chunks of matter (alpha particles or beta particles), high-energy radiation (gamma rays), or both at a fixed rate. A particular radioactive isotope may emit any one or a combination of
radioactive isotopes or radioisotopes
unstable isotopes
reliable science
consists of data, hypotheses, theories, and laws that are widely accepted by scientists who are considered experts in the field under study.
science
an endeavor to discover how nature works and to use that knowledge to make predictions about what is likely to happen in nature.
scientific hypothesis
a possible and testable explanation of what they observe in nature or in the results of their experiments.
scientific law, or law of nature
a well-tested and widely accepted description of what we find happening over and over again in the same way in nature
scientific theory
A well-tested and widely accepted scientific hypothesis or a group of related hypotheses
second law of thermodynamics
When energy changes from one form to another, we always end up with lower-quality or less usable energy than we started with. This lower-quality energy usually takes the form of heat given off at a low temperature to the environment.
synergistic interaction, or synergy
occurs when two or more processes interact so that the combined effect is greater than the sum of their separate effects.
system
a set of components that function and interact in some regular way.
tentative science or frontier science
Sometimes, preliminary results that capture news headlines are controversial because they have not been widely tested and accepted by peer review. They are not yet considered reliable, and can be thought of as tentative science or frontier science.
time delays
Complex systems often show time delays between the input of a feedback stimulus and the response to it.
tipping point
Time delays can allow an environmental problem to build slowly until it reaches a threshold level, or tipping point, causing a fundamental shift in the behavior of a system
trait
Each of these coded units of genetic information concerns a specific trait, or characteristic passed on from parents to offspring during reproduction in an animal or plant.
unreliable science
Scientific hypotheses and results that are presented as reliable without having undergone the rigors of peer review, or that have been discarded as a result of peer review, are considered to be unreliable science