Junkao Science Knowledge key terms

A testable, falsifiable statement predicting the relationship between variables, written before data collection so that results can either support or contradict it.

The factor a researcher deliberately changes or selects across treatment groups, so that its effect on the measured outcome can be observed.

The outcome that is measured in an experiment; its value is expected to respond to changes in the factor the researcher manipulates.

A comparison group that receives no treatment or a neutral treatment, establishing the baseline against which the effects of the experimental treatment are judged.

A study in which all variables except the one being tested are held constant, so that observed differences can be attributed to the manipulated factor.

A broad, well-tested explanation for a body of evidence that has survived repeated attempts at falsification and unifies many observations and laws.

Evaluation of a study's methods and conclusions by independent experts before publication, intended to catch errors and unsupported claims.

The number of independent observations or subjects in a study; larger samples generally reduce the influence of chance variation on conclusions.

A statistical relationship in which two variables tend to change together; it does not by itself establish that one causes the other.

Standard multipliers attached to SI units, such as kilo (1000), centi (0.01), milli (0.001), and micro (0.000001), used to scale measurements conveniently.

The internationally agreed measurement system built on seven base units, including the meter, kilogram, second, ampere, kelvin, mole, and candela.

A unit formed by combining base units through multiplication or division, such as the newton (kg·m/s²) for force or the watt for power.

The digits in a measurement that carry meaningful information about its precision, including all certain digits plus one estimated digit.

A way of writing numbers as a coefficient between 1 and 10 multiplied by a power of ten, convenient for very large or very small quantities.

Mass per unit volume of a substance, calculated by dividing mass by volume and commonly expressed in grams per cubic centimeter.

Accuracy describes how close a measurement is to the true value, while precision describes how closely repeated measurements agree with one another.

The smallest unit of an element that retains that element's chemical 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 listed on the periodic table.

A substance formed when atoms of two or more different elements bond in fixed proportions, with properties unlike those of its constituent elements.

Two or more atoms held together by covalent bonds; a molecule may contain atoms of one element or of several different elements.

A process in which bonds break and form so that reactant substances rearrange into new products, conserving atoms but not necessarily properties.

The principle that the total mass of substances is unchanged in a chemical reaction because atoms are neither created nor destroyed.

A characteristic observable or measurable without changing a substance's chemical identity, such as density, melting point, or color.

A push or pull acting on an object, capable of changing its motion or shape; measured in newtons and having both magnitude and direction.

Three principles describing motion: inertia without net force, acceleration proportional to net force and inversely to mass, and equal and opposite action-reaction pairs.

A contact force that opposes relative motion or the tendency to move between surfaces, converting kinetic energy into thermal energy.

The energy an object possesses because of its motion, calculated as one-half its mass times the square of its speed.

Stored energy determined by an object's position or configuration, such as the energy of a raised mass or a stretched spring.

The principle that energy cannot be created or destroyed but only transferred or transformed between forms, keeping total energy constant in a closed system.

A disturbance that transfers energy through space or a medium without permanently displacing the medium itself.

Wavelength is the distance between successive wave crests; frequency is the number of cycles passing a point per second, and the two are inversely related.

The full range of electromagnetic radiation ordered by wavelength, from long radio waves through microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.

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

The electric potential difference between two points, measured in volts, that supplies the energy per unit charge driving current through a circuit.

Opposition to the flow of electric current in a material, measured in ohms and determined by material, length, and cross-sectional area.

A region around a magnet or moving charge where magnetic forces act on other magnets or moving charges, represented by field lines from north to south.

A selectively permeable phospholipid bilayer surrounding a cell that controls which substances enter and leave.

The smallest structural and functional unit of life, bounded by a membrane and containing genetic material and cytoplasm.

A double-stranded molecule of nucleotides that stores genetic instructions in its base sequence and is copied before cell division.

A segment of DNA that carries the instructions for producing a functional product, often a protein, and is inherited from parent to offspring.

One of the alternative versions of a gene at a given position on a chromosome, which may produce different observable traits.

The process by which heritable traits that improve survival and reproduction become more common in a population over successive generations.

A heritable feature or behavior that enhances an organism's ability to survive and reproduce in its particular environment.

The diffusion of water across a selectively permeable membrane from a region of higher water concentration to one of lower water concentration.

A community of interacting organisms together with the nonliving physical environment in which they live and exchange matter and energy.

A network of interconnected feeding relationships showing how energy and matter move among producers, consumers, and decomposers in an ecosystem.

The process by which plants, algae, and some bacteria use light energy to convert carbon dioxide and water into glucose and oxygen.

The movement of carbon among the atmosphere, oceans, soil, and living organisms through processes including photosynthesis, respiration, and combustion.

The maximum population size of a species that a given environment can sustain indefinitely with the resources available.

The variety of species, genetic variation within species, and ecosystem types present in a region, which supports ecosystem stability and resilience.

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

The theory that Earth's rigid outer shell is divided into plates that move on the underlying mantle, causing earthquakes, volcanoes, and mountain building.

Ground shaking produced when built-up stress in crustal rock is suddenly released along a fault, radiating seismic waves.

The ongoing transformation of rock among igneous, sedimentary, and metamorphic forms through melting, cooling, weathering, erosion, and heat and pressure.

Weathering breaks rock down in place by physical or chemical means, while erosion transports the resulting fragments elsewhere.

The continuous circulation of water among oceans, atmosphere, and land through evaporation, condensation, precipitation, and runoff.

Annual variations in daylight and temperature caused by the tilt of Earth's axis as the planet orbits the Sun, not by distance from the Sun.

The Sun and all bodies gravitationally bound to it, including planets, moons, asteroids, and comets orbiting in roughly the same plane.

A mutual attractive force between masses that governs falling objects, orbits, and the large-scale structure of the universe.