VALID Science 10 key terms

A testable, falsifiable statement that predicts the outcome of an experiment under specific conditions. It must be worded so that evidence could show it to be wrong.

The factor that a researcher deliberately changes or selects in an experiment, so its effect on the measured outcome can be observed.

The factor that is measured or observed in an experiment; its value is expected to depend on how the independent variable is set.

A test in which all factors except the independent variable are held constant, so any change in the outcome can be attributed to that one factor.

The comparison group in an experiment that does not receive the treatment being tested, providing a baseline against which the treated group's results are judged.

The degree to which repeated measurements or repeated trials give consistent results. Reliable data can still be inaccurate if a systematic error is present.

How close a measured value is to the true or accepted value. Accuracy differs from precision, which concerns how closely repeated measurements agree with each other.

A judgment about whether the results support the hypothesis, based only on the collected evidence and acknowledging sources of error or uncertainty.

The smallest unit of an element that retains that element's properties, consisting of a nucleus of protons and neutrons surrounded by electrons.

A pure substance made of only one kind of atom, defined by its atomic number and unable to be broken into simpler substances by chemical means.

The number of protons in the nucleus of an atom, which uniquely identifies the element and determines its position on the periodic table.

A positively charged particle found in the atomic nucleus. Its count equals the atomic number and, in a neutral atom, the number of electrons.

An electrically neutral particle in the atomic nucleus. Atoms of the same element can differ in neutron number, forming isotopes.

A negatively charged particle that occupies energy levels around the nucleus and participates in bonding and chemical reactions.

One of two or more atoms of the same element that have equal proton numbers but different neutron numbers, and therefore different mass numbers.

An arrangement of elements in order of increasing atomic number, organized so that elements with similar chemical properties fall into the same vertical groups.

An electron in the outermost occupied energy level of an atom. These electrons chiefly determine how the atom bonds and reacts.

An atom or group of atoms that has gained or lost electrons, giving it a net positive or negative electrical charge.

A process in which substances are transformed into new substances with different properties, as atoms are rearranged and bonds are broken and formed.

A starting substance in a chemical reaction that is consumed as the reaction proceeds and appears on the left side of a written equation.

A substance formed by a chemical reaction, appearing on the right side of a written equation and having properties unlike the reactants.

The principle that the total mass of the reactants equals the total mass of the products in a closed system, because atoms are neither created nor destroyed.

A chemical equation in which coefficients are adjusted so that each kind of atom appears in equal numbers on both sides, reflecting conservation of mass.

A pure substance formed when two or more different elements are chemically bonded in fixed proportions, with properties unlike those of its elements.

The electrical attraction that holds oppositely charged ions together, typically formed when a metal transfers electrons to a nonmetal.

A bond formed when two atoms share one or more pairs of electrons, usually between nonmetals, producing molecules rather than separate ions.

A notation using element symbols and subscript numbers to show the kinds and relative numbers of atoms in a compound or molecule.

The distance an object travels per unit of time, a scalar quantity that has magnitude but no direction.

The rate at which an object changes position in a stated direction; a vector quantity that includes both speed and direction.

The rate at which velocity changes with time, occurring when an object speeds up, slows down, or changes direction.

A push or a pull that can change an object's motion or shape, measured in newtons and having both magnitude and direction.

Three principles describing how forces affect motion: inertia, the relation between force, mass and acceleration, and equal and opposite action-reaction pairs.

The rate at which electric charge flows past a point in a circuit, measured in amperes and driven by a potential difference.

The electrical potential difference between two points that drives current through a circuit, measured in volts.

A material's opposition to the flow of electric current, measured in ohms and depending on the material, length, and thickness.

A circuit in which components are connected in a single path, so the same current passes through each and one break stops all flow.

The theory that Earth's rigid outer shell is broken into large plates that move over the mantle, causing earthquakes, volcanoes, and mountain building at their boundaries.

A plate boundary where two plates move toward each other, producing subduction, mountain belts, deep ocean trenches, and often powerful earthquakes.

Ground shaking caused by the sudden release of stored energy when rock breaks or slips along a fault within Earth's crust.

The layer of gases held by gravity around a planet, which stores heat, carries weather, and shields the surface from harmful radiation.

The short-term condition of the atmosphere at a particular place, described by temperature, humidity, precipitation, wind, and air pressure.

The long-term average pattern of weather in a region, including typical conditions and their variation over decades or more.

The warming of a planet's surface as certain atmospheric gases absorb and re-emit outgoing infrared radiation, trapping heat near the ground.

The smallest unit of life, bounded by a membrane, that can carry out the basic processes needed to sustain living things.

The selectively permeable barrier around a cell that controls which substances enter and leave, allowing the cell to maintain internal conditions.

The net movement of particles from an area of higher concentration to lower concentration, driven by random motion and requiring no energy input.

A type of cell division producing two genetically identical daughter cells, used for growth, repair, and replacement in multicellular organisms.

A cell division that halves the chromosome number and produces genetically varied gametes for sexual reproduction.

One of the alternative versions of a gene that an organism may inherit, which can lead to different observable traits.

A trait that is expressed in an organism's appearance whenever at least one copy of its allele is inherited, masking the recessive form.

A community of interacting organisms together with the nonliving parts of their environment, through which energy and matter flow.

A model of overlapping feeding relationships in an ecosystem that shows how energy and matter move from producers to various consumers.

The largest population size an environment can support indefinitely, given the food, water, space, and other resources available.

Meeting present needs for resources without depleting or degrading the systems that future generations will depend on.